Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

Spring,
Yes, the image shift by the JOSM "Imagery offset" button is not saved on
the server. It is only evident on the local computer. The Imagery Offset DB
is used to store offsets that should be used by others. It is a manual
process to check the Offset DB, to see if one applies in the area you are
mapping. The Offset DB wouldn't apply to the DG images I've used since
their offsets vary from place-to-place in the same tile, due to the steep
terrain.

Cheers ... Steve

On Sun, May 10, 2015 at 8:08 AM, john whelan  wrote:

> Bing buys images from satellite operators, DigitalGlobe is a satellite
> operator that is nice enough to release some images directly to us
> occasionally and Kevin even does some mapping from time to time.
>
> Since Bing does not have high resolution imagery for everywhere we map HOT
> obtains images from many sources sometimes an Agency will buy images and
> let us have access.
>
> Cheerio John
>
> On 10 May 2015 at 01:19, Springfield Harrison 
> wrote:
>
>> OK, thanks Kevin.  So someone not paying attention to this level of
>> detail might not actually know if they're using a Bing or DG image?
>> However, the word is to use Bing as the positional standard.  This sounds
>> like a potential procedural problem.  Then in JOSM, if the layer list says
>> Bing, then it is Bing?  Or do we use the copyright designation on the image
>> itself?  Which might contradict the designation in the layer list.
>>
>> Thanks, Cheers . . . . . . . . Spring
>>
>>
>> At 09-05-2015 07:30 Saturday, Kevin Bullock wrote:
>>
>>> >>Does Digital Globe supply Bing images? Just curious, they are always
>>> referred to as different products.
>>>
>>> Yes, Microsoft licenses DigitalGlobe imagery for many parts of the
>>> world, you'll notice the attribution in the Bing Maps platform. In various
>>> threads, I've seen Bing imagery "versus" DigitalGlobe imagery, and that is
>>> usually a contradiction. The proper way of characterizing it is:
>>> DigitalGlobe imagery through the Bing platform versus DigitalGlobe imagery
>>> being made available during this crisis.
>>> https://www.digitalglobe.com/partners/platform-partners/microsoft
>>>
>>> Cheers, Kevin
>>>
>>>
>>> This electronic communication and any attachments may contain
>>> confidential and proprietary information of DigitalGlobe, Inc. If you are
>>> not the intended recipient, or an agent or employee responsible for
>>> delivering this communication to the intended recipient, or if you have
>>> received this communication in error, please do not print, copy,
>>> retransmit, disseminate or otherwise use the information. Please indicate
>>> to the sender that you have received this communication in error, and
>>> delete the copy you received.
>>>
>>> DigitalGlobe reserves the right to monitor any electronic communication
>>> sent or received by its employees, agents or representatives.
>>>
>>
>>
>> ___
>> HOT mailing list
>> HOT@openstreetmap.org
>> https://lists.openstreetmap.org/listinfo/hot
>>
>
>
> ___
> HOT mailing list
> HOT@openstreetmap.org
> https://lists.openstreetmap.org/listinfo/hot
>
>
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[john whelan]

Bing buys images from satellite operators, DigitalGlobe is a satellite
operator that is nice enough to release some images directly to us
occasionally and Kevin even does some mapping from time to time.

Since Bing does not have high resolution imagery for everywhere we map HOT
obtains images from many sources sometimes an Agency will buy images and
let us have access.

Cheerio John

On 10 May 2015 at 01:19, Springfield Harrison  wrote:

> OK, thanks Kevin.  So someone not paying attention to this level of detail
> might not actually know if they're using a Bing or DG image?  However, the
> word is to use Bing as the positional standard.  This sounds like a
> potential procedural problem.  Then in JOSM, if the layer list says Bing,
> then it is Bing?  Or do we use the copyright designation on the image
> itself?  Which might contradict the designation in the layer list.
>
> Thanks, Cheers . . . . . . . . Spring
>
>
> At 09-05-2015 07:30 Saturday, Kevin Bullock wrote:
>
>> >>Does Digital Globe supply Bing images? Just curious, they are always
>> referred to as different products.
>>
>> Yes, Microsoft licenses DigitalGlobe imagery for many parts of the world,
>> you'll notice the attribution in the Bing Maps platform. In various
>> threads, I've seen Bing imagery "versus" DigitalGlobe imagery, and that is
>> usually a contradiction. The proper way of characterizing it is:
>> DigitalGlobe imagery through the Bing platform versus DigitalGlobe imagery
>> being made available during this crisis.
>> https://www.digitalglobe.com/partners/platform-partners/microsoft
>>
>> Cheers, Kevin
>>
>>
>> This electronic communication and any attachments may contain
>> confidential and proprietary information of DigitalGlobe, Inc. If you are
>> not the intended recipient, or an agent or employee responsible for
>> delivering this communication to the intended recipient, or if you have
>> received this communication in error, please do not print, copy,
>> retransmit, disseminate or otherwise use the information. Please indicate
>> to the sender that you have received this communication in error, and
>> delete the copy you received.
>>
>> DigitalGlobe reserves the right to monitor any electronic communication
>> sent or received by its employees, agents or representatives.
>>
>
>
> ___
> HOT mailing list
> HOT@openstreetmap.org
> https://lists.openstreetmap.org/listinfo/hot
>
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

Hello Steve,
Thanks for that clarification, I think I get the distinctions.  Are
you saying that the image shift is not saved, it is only evident on the
local computer?  So other users would not see that change, is that
correct?
However, there is an image shift database which implies that the shifts
are permanent and could be documented.
Yes, I was aware of the off-nadir angle problem but didn't realize it was
an issue here.  As you know, the "best" part of the image
is near the center, the off-nadir approach is like looking past the far
edge of the photo!  Necessary in this case, I suppose.
Sorry to be a bit obtuse, but this image shifting practice is new to
me.
Thanks
again, Cheers . . . . . . . . Spring

At 09-05-2015 11:03 Saturday, Steve Bower wrote:
Spring,
When I talk about "moving the imagery" that is only to align it
with Bing imagery as I work in a very localized area, in order to confirm
that the features are (roughly) correctly located, relative to Bing. It
does not change the geo-referencing of the underlying data for other
users - it is only revising it for my display. I expect that how you
understood it, but in case that wasn't clear. 
I haven't personally digitized anything from the DG imagery. I have only
used it to help with interpretation where the Bing imagery is poor (low
res or cloudy). But others may be locating features from the DG imagery -
hopefully only experienced mappers with careful reference to better
geo-rectified imagery ("hopefully" being the aspect that gives
us all concern, of course).
I fully agree this is not "best practice" for digital mapping -
it's "best available" within resource constraints for crisis
response.
By the way, you may already be very familiar with this, but the elevation
aspect of ortho-rectification is described here (see image at top-right):

http://en.wikipedia.org/wiki/Orthophoto. Or see the first image in
this page:

http://www.kevinroper.org/portfolio/ . These explain why the more
severe off-nadir angle causes greater location distortion, more difficult
to correct for. 

On Sat, May 9, 2015 at 10:30 AM, Kevin Bullock
<
kbull...@digitalglobe.com> wrote:


>>Does Digital Globe supply Bing images?  Just curious, they
are always referred to as different products.

Yes, Microsoft licenses DigitalGlobe imagery for many parts of the
world, you’ll notice the attribution in the Bing Maps platform. In
various threads, I’ve seen Bing imagery “versus” DigitalGlobe
imagery, and that is usually a contradiction. The proper way of
characterizing it is: DigitalGlobe imagery through the Bing platform
versus DigitalGlobe imagery being made available during this crisis.

https://www.digitalglobe.com/partners/platform-partners/microsoft


Cheers, Kevin


This electronic communication and any attachments may contain
confidential and proprietary information of DigitalGlobe, Inc. If you are
not the intended recipient, or an agent or employee responsible for
delivering this communication to the intended recipient, or if you have
received this communication in error, please do not print, copy,
retransmit, disseminate or otherwise use the information. Please indicate
to the sender that you have received this communication in error, and
delete the copy you received.

DigitalGlobe reserves the right to monitor any electronic
communication sent or received by its employees, agents or
representatives.





___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

OK, thanks Kevin.  So someone not paying attention to this level of 
detail might not actually know if they're using a Bing or DG 
image?  However, the word is to use Bing as the positional 
standard.  This sounds like a potential procedural problem.  Then in 
JOSM, if the layer list says Bing, then it is Bing?  Or do we use the 
copyright designation on the image itself?  Which might contradict 
the designation in the layer list.


Thanks, Cheers . . . . . . . . Spring


At 09-05-2015 07:30 Saturday, Kevin Bullock wrote:
>>Does Digital Globe supply Bing images? Just curious, they are 
always referred to as different products.


Yes, Microsoft licenses DigitalGlobe imagery for many parts of the 
world, you'll notice the attribution in the Bing Maps platform. In 
various threads, I've seen Bing imagery "versus" DigitalGlobe 
imagery, and that is usually a contradiction. The proper way of 
characterizing it is: DigitalGlobe imagery through the Bing platform 
versus DigitalGlobe imagery being made available during this crisis. 
https://www.digitalglobe.com/partners/platform-partners/microsoft


Cheers, Kevin


This electronic communication and any attachments may contain 
confidential and proprietary information of DigitalGlobe, Inc. If 
you are not the intended recipient, or an agent or employee 
responsible for delivering this communication to the intended 
recipient, or if you have received this communication in error, 
please do not print, copy, retransmit, disseminate or otherwise use 
the information. Please indicate to the sender that you have 
received this communication in error, and delete the copy you received.


DigitalGlobe reserves the right to monitor any electronic 
communication sent or received by its employees, agents or representatives.



___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

Spring,
When I talk about "moving the imagery" that is only to align it with Bing
imagery as I work in a very localized area, in order to confirm that the
features are (roughly) correctly located, relative to Bing. It does not
change the geo-referencing of the underlying data for other users - it is
only revising it for my display. I expect that how you understood it, but
in case that wasn't clear.

I haven't personally digitized anything from the DG imagery. I have only
used it to help with interpretation where the Bing imagery is poor (low res
or cloudy). But others may be locating features from the DG imagery -
hopefully only experienced mappers with careful reference to better
geo-rectified imagery ("hopefully" being the aspect that gives us all
concern, of course).

I fully agree this is not "best practice" for digital mapping - it's "best
available" within resource constraints for crisis response.

By the way, you may already be very familiar with this, but the elevation
aspect of ortho-rectification is described here (see image at top-right):
http://en.wikipedia.org/wiki/Orthophoto. Or see the first image in this
page: http://www.kevinroper.org/portfolio/ . These explain why the more
severe off-nadir angle causes greater location distortion, more difficult
to correct for.



On Sat, May 9, 2015 at 10:30 AM, Kevin Bullock 
wrote:

> >>Does Digital Globe supply Bing images?  Just curious, they are always
> referred to as different products.
>
> Yes, Microsoft licenses DigitalGlobe imagery for many parts of the world,
> you’ll notice the attribution in the Bing Maps platform. In various
> threads, I’ve seen Bing imagery “versus” DigitalGlobe imagery, and that is
> usually a contradiction. The proper way of characterizing it is:
> DigitalGlobe imagery through the Bing platform versus DigitalGlobe imagery
> being made available during this crisis.
> https://www.digitalglobe.com/partners/platform-partners/microsoft
>
> Cheers, Kevin
>
>
> This electronic communication and any attachments may contain confidential
> and proprietary information of DigitalGlobe, Inc. If you are not the
> intended recipient, or an agent or employee responsible for delivering this
> communication to the intended recipient, or if you have received this
> communication in error, please do not print, copy, retransmit, disseminate
> or otherwise use the information. Please indicate to the sender that you
> have received this communication in error, and delete the copy you received.
>
> DigitalGlobe reserves the right to monitor any electronic communication
> sent or received by its employees, agents or representatives.
>
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Kevin Bullock]

>>Does Digital Globe supply Bing images?  Just curious, they are always 
>>referred to as different products.

Yes, Microsoft licenses DigitalGlobe imagery for many parts of the world, 
you’ll notice the attribution in the Bing Maps platform. In various threads, 
I’ve seen Bing imagery “versus” DigitalGlobe imagery, and that is usually a 
contradiction. The proper way of characterizing it is: DigitalGlobe imagery 
through the Bing platform versus DigitalGlobe imagery being made available 
during this crisis. 
https://www.digitalglobe.com/partners/platform-partners/microsoft

Cheers, Kevin


This electronic communication and any attachments may contain confidential and 
proprietary information of DigitalGlobe, Inc. If you are not the intended 
recipient, or an agent or employee responsible for delivering this 
communication to the intended recipient, or if you have received this 
communication in error, please do not print, copy, retransmit, disseminate or 
otherwise use the information. Please indicate to the sender that you have 
received this communication in error, and delete the copy you received.

DigitalGlobe reserves the right to monitor any electronic communication sent or 
received by its employees, agents or representatives.

___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

ut
images of high distortion and displacement.  This would certainly reduce
the volume of deliverable images but at least a higher quality standard
would be maintained.  I have great difficulty adopting the concept that
any data is better than none.  Bad data can lead to bad decisions, not a
good prospect in a major disaster relief exercise.

In GPS mapping, we set PDOP and SNR thresholds and collect no data
when those thresholds are exceeded - such is life.  Those down times are
fairly predictable and are used for lunch, etc.

Are your satellite orbits geostationary or do they move
longitude-wise with each pass?  If so, they must be overhead Nepal
occasionally at least.  Presumably this would allow for higher accuracy
georeferencing during those passes.

Anyway, people seem content with this process of rearranging the
Earth's surface at will and I can only assume that the end-users are
content with the outcome.

Thank you again for your explanation, always good to understand what
others are up to.

                 Cheers . . . . . . . . Spring
Harrison



At 07-05-2015 13:28 Thursday, Kevin Bullock wrote:

Content-Language: en-US

Content-Type: multipart/related;

        
boundary="_005_04736300ae6442c49b5befd127570df2PW00INFMAI021entaddgloc_";

         type="multipart/alternative"

This is a great thread and I wanted to provide some additional
information on behalf of DigitalGlobe:

 

1)Â Â Â Â  Our goal in collecting imagery and making it available via
open license is to provide as much data as possible given the
humanitarian nature of this event. This means we use our satellites in a
manner not typically seen. Charlie did a great job summarizing this in
his recent blog [1]

2)Â Â Â Â  Given this, we are actually swiveling our satellites to
“point†at Nepal even ven when our orbits are not directly over
Nepal. As an example, a satellite may be vertically overhead Bangladesh,
yet, the satellite is looking back at Nepal. This is actually quantified
and measured in the image metadata by referencing the Off Nadir
Angle[2] and Target Azimuth. In typical circumstances, best
accuracy is achieved when Off Nadir angle is less than 20 degrees. In
these cases, the ground RMSE is within a few meters [3] . However,
the events in Nepal are not considered to by typical circumstances, and
in some cases, we are pushing Off Nadir Angles above 40 degrees. 

3)Â Â Â Â  I wanted to confirm that all imagery is indeed
ortho-rectified and geo-corrected to the best of our ability considering
timeliness and the fact many many people and organizations are waiting
for imagery and heavily dependent on its availability. In our
orthorectification process, we are leveraging a variety of elevation
models. Important to note that most elevation models have linear error
that can range from 5-15m. [4] As the off nadir angle increases,
these inaccuracies in the elevation model propagate into horizontal
displacements in the imagery. This is why we are seeing large offsets.


4)Â Â Â Â  The tradeoff here is timely, massive amounts of post event
imagery acquired under less than ideal circumstances containing
horizontal error, or, very limited imagery only collected under ideal
circumstances with minimal horizontal error. As noted below, typically,
the former is preferred. 

 

Hope this helps, Kevin

 

[1] -

https://www.mapbox.com/blog/nepal-imagery-collection/ 

[2] -

http://www.landinfo.com/buying-optical-satellite-imagery-2.html 

[3] -

https://www.digitalglobe.com/sites/default/files/WorldView_Geolocation_Accuracy.pdf
 

[4] -

http://www.satimagingcorp.com/services/orthorectification/ 

 

From: Steve Bower [

mailto:sbo...@gmavt.net] 

Sent: Thursday, May 07, 2015 10:49 AM

To: Milo van der Linden

Cc: Heather Leson;
i...@hotosm.org; Ross Taylor;
HOT@OSM (Humanitarian OpenStreetMap Team)

Subject: Re: [HOT] [info-hotosm] Reference Project #1030 Nepal
Earthquake

 

Springfield,

You raise important points, and are not "raining on a
parade". The resulting data will not be suitable for all purposes,
but it can be very useful for this crisis response.

 

I do think there is significant risk that some mappers will map
directly from un-rectified imagery, and introduce problematic location
errors. That needs to be minimized, e.g., through clear instructions and
good validation. I think there's room for improvement on the
instructions, e.g., it would be good to have a wiki page on mapping from
un-rectified imagery in combination with rectified imagery, for crisis
response.

 

Thanks

 

On Thu, May 7, 2015 at 5:14 AM, Milo van der Linden
<m...@dogodigi.net>
wrote:

Hello Springfield Harrison,

As a 20 year GIS veteran I understand what you say. I do agree that
in communication with first responders it is important to have them
clearly understand that the accuracy of features can be off ~100m. But
for them having maps that give a good indic

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

Hi Kevin,
Thanks for
your reply.  Interesting perspectives on a new (to me) GIS
culture.
In JOSM, I
noticed that although the Bing air photo layer was turned on, the photo
itself was labeled Digital Globe.  Does Digital Globe supply Bing
images?  Just curious, they are always referred to as different
products.

Thanks, Cheers .
. . . . . . . Spring

At 08-05-2015 09:04 Friday, Kevin Bullock wrote:
>>it still concerns me
that untrained users can move the imagery around at a whim
completely agreed; not only in this Nepal activation but for all
OpenStreetMap work!
>>Perhaps a lower cutoff angle could be adopted to filter out
images of high distortion and displacement.
this is our typical operational procedure, so the imagery you’ll see in
Bing Maps, and Mapbox Satellite has these characteristics. 
>>Are your satellite orbits geostationary or do they move
longitude-wise with each pass? 
our satellites (and most Earth Oberservation satellites) are in “Low
Earth Orbit” at around 600-800 km. By comparison, Geostationary is over
35,000 km! Geo is far too distant to make high resolution observations.
DigitalGlobe satellites are in a Sun Synchronous orbit meaning they orbit
from North Pole to South Pole in an approximate 90 min revolution. So
each satellite makes about 15 Earth orbits per day. In fact, all of the
orbit information is public domain data found here:
http

://www.celestrak.com/NORAD/elements/master.asp  
Regards, Kevin 
This electronic communication and any attachments may contain
confidential and proprietary information of DigitalGlobe, Inc. If you are
not the intended recipient, or an agent or employee responsible for
delivering this communication to the intended recipient, or if you have
received this communication in error, please do not print, copy,
retransmit, disseminate or otherwise use the information. Please indicate
to the sender that you have received this communication in error, and
delete the copy you received. 
DigitalGlobe reserves the right to monitor any electronic communication
sent or received by its employees, agents or representatives.




___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Kevin Bullock]

>>it still concerns me that untrained users can move the imagery around at a 
>>whim

completely agreed; not only in this Nepal activation but for all OpenStreetMap 
work!

>>Perhaps a lower cutoff angle could be adopted to filter out images of high 
>>distortion and displacement.

this is our typical operational procedure, so the imagery you’ll see in Bing 
Maps, and Mapbox Satellite has these characteristics.

>>Are your satellite orbits geostationary or do they move longitude-wise with 
>>each pass?

our satellites (and most Earth Oberservation satellites) are in “Low Earth 
Orbit” at around 600-800 km. By comparison, Geostationary is over 35,000 km! 
Geo is far too distant to make high resolution observations. DigitalGlobe 
satellites are in a Sun Synchronous orbit meaning they orbit from North Pole to 
South Pole in an approximate 90 min revolution. So each satellite makes about 
15 Earth orbits per day. In fact, all of the orbit information is public domain 
data found here: http://www.celestrak.com/NORAD/elements/master.asp

Regards, Kevin

This electronic communication and any attachments may contain confidential and 
proprietary information of DigitalGlobe, Inc. If you are not the intended 
recipient, or an agent or employee responsible for delivering this 
communication to the intended recipient, or if you have received this 
communication in error, please do not print, copy, retransmit, disseminate or 
otherwise use the information. Please indicate to the sender that you have 
received this communication in error, and delete the copy you received.

DigitalGlobe reserves the right to monitor any electronic communication sent or 
received by its employees, agents or representatives.
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

by
> typical circumstances, and in some cases, we are pushing Off Nadir Angles
> above 40 degrees.
> 3) I wanted to confirm that all imagery is indeed ortho-rectified and
> geo-corrected to the best of our ability considering timeliness and the
> fact many many people and organizations are waiting for imagery and heavily
> dependent on its availability. In our orthorectification process, we are
> leveraging a variety of elevation models. Important to note that most
> elevation models have linear error that can range from 5-15m. [4] As the
> off nadir angle increases, these inaccuracies in the elevation model
> propagate into horizontal displacements in the imagery. This is why we are
> seeing large offsets.
> 4) The tradeoff here is timely, massive amounts of post event imagery
> acquired under less than ideal circumstances containing horizontal error,
> or, very limited imagery only collected under ideal circumstances with
> minimal horizontal error. As noted below, typically, the former is
> preferred.
>
> Hope this helps, Kevin
>
> [1] - https://www.mapbox.com/blog/nepal-imagery-collection/
> [2] - http://www.landinfo.com/buying-optical-satellite-imagery-2.html
> [3] -
> https://www.digitalglobe.com/sites/default/files/WorldView_Geolocation_Accuracy.pdf
> [4] - http://www.satimagingcorp.com/services/orthorectification/
>
> *From:* Steve Bower [ mailto:sbo...@gmavt.net ]
> *Sent:* Thursday, May 07, 2015 10:49 AM
> *To:* Milo van der Linden
> *Cc:* Heather Leson; i...@hotosm.org; Ross Taylor; HOT@OSM (Humanitarian
> OpenStreetMap Team)
> *Subject:* Re: [HOT] [info-hotosm] Reference Project #1030 Nepal
> Earthquake
>
> Springfield,
> You raise important points, and are not "raining on a parade". The
> resulting data will not be suitable for all purposes, but it can be very
> useful for this crisis response.
>
> I do think there is significant risk that some mappers will map directly
> from un-rectified imagery, and introduce problematic location errors. That
> needs to be minimized, e.g., through clear instructions and good
> validation. I think there's room for improvement on the instructions, e.g.,
> it would be good to have a wiki page on mapping from un-rectified imagery
> in combination with rectified imagery, for crisis response.
>
> Thanks
>
> On Thu, May 7, 2015 at 5:14 AM, Milo van der Linden 
> wrote:
> Hello Springfield Harrison,
> As a 20 year GIS veteran I understand what you say. I do agree that in
> communication with first responders it is important to have them clearly
> understand that the accuracy of features can be off ~100m. But for them
> having maps that give a good indication is way better then having no maps
> at all. In the end, and that is what I hope for, it can save lives.
> I have a long running discussion with y'olde GIS community on "how can a
> map created by amateurs be better then what we professionals do?". It is my
> opinion that it can be. I believe that "the many are smarter than the few"
> (quote by James Surowiecki). And the HOT tasks have all the ingredients to
> succeed:
> 1. There is diversity of opinion
> 2. People involved in the mapping process have opinions not influenced by
> those around them
> 3. People operate decentralized
> The only thing that might need more attention (and this is where
> geospatial experts can take their role) is that HOT and openstreetmap as a
> whole could use more mechanisms to turn all these little "private
> judgements" into collective quality. This process could involve analysing
> quantity and different representations of the same feature through time. In
> that way, you could see the mapping activity (in dense area's) as GPS.
> There are faults, influenced by methodology, opinion and conditions. And as
> a GPS professional, you know that it is _knowing the error_ that
> automagically creates accuracy. I would love the GIS/GPS community to think
> about how to know the error in community mapping.
> I love this new way of mapping. It creates new opportunities. It involves
> new ways of thinking. It is not influenced by what GIS people say GIS
> should be like.
> Kind regards, with respect,
> Milo
>
>
>  https://en.wikipedia.org/wiki/The_Wisdom_of_Crowds
>
> 2015-05-07 10:21 GMT+02:00 Springfield Harrison :
> Hello Steve,
>
> Sorry to rain on the parade yet again but I find this matter of
> image alignment to be puzzling and concerning.
>
> One of the first things I learned when embarking upon GIS/GPS
> mapping was that accurate georeferencing of all layers, but especially the
> base layers (imagery in this case) was sacrosanct. If things are not in
> their correct point in spac

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

Hello Kevin,
Thanks very much for your very helpful memo regarding image
quality.  It is very useful for now the challenges that you face in
your methods for getting the best quality data out to OSM and
others.  I will have a look at your reference articles as time
permits.
Although I now better understand why some of the imagery is displaced, it
still concerns me that untrained users can move the imagery around at a
whim.  Essentially, this means that each user is creating their own
map datum, to me, a recipe for disaster.
If, in certain cases, offsets are deemed to be desirable, perhaps they
should be applied over a broad area, uniformly by the GIS management
crew.  This would introduce a degree of control and consistency that
seems to be completely absent now.
Although I don't know a lot about photogrammetry, an Off Nadir Angle of
40° or more does seem extreme, especially in areas of such high
relief.  Perhaps a lower cutoff angle could be adopted to filter out
images of high distortion and displacement.  This would certainly
reduce the volume of deliverable images but at least a higher quality
standard would be maintained.  I have great difficulty adopting the
concept that any data is better than none.  Bad data can lead to bad
decisions, not a good prospect in a major disaster relief
exercise.
In GPS mapping, we set PDOP and SNR thresholds and collect no data when
those thresholds are exceeded - such is life.  Those down times are
fairly predictable and are used for lunch, etc.
Are your satellite orbits geostationary or do they move longitude-wise
with each pass?  If so, they must be overhead Nepal occasionally at
least.  Presumably this would allow for higher accuracy
georeferencing during those passes.
Anyway, people seem content with this process of rearranging the Earth's
surface at will and I can only assume that the end-users are content with
the outcome.
Thank you again for your explanation, always good to understand what
others are up to.

Cheers . . . . .
. . . Spring Harrison


At 07-05-2015 13:28 Thursday, Kevin Bullock wrote:
Content-Language: en-US
Content-Type: multipart/related;

boundary="_005_04736300ae6442c49b5befd127570df2PW00INFMAI021entaddgloc_";

type="multipart/alternative"
This is a great thread and I wanted to provide some additional
information on behalf of DigitalGlobe:
 
1)  Our goal in collecting imagery and making it
available via open license is to provide as much data as possible given
the humanitarian nature of this event. This means we use our satellites
in a manner not typically seen. Charlie did a great job summarizing this
in his recent blog [1]
2)  Given this, we are actually swiveling
our satellites to “point” at Nepal even when our orbits are not
directly over Nepal. As an example, a satellite may be vertically
overhead Bangladesh, yet, the satellite is looking back at Nepal. This is
actually quantified and measured in the image metadata by referencing the
Off Nadir Angle[2] and Target Azimuth. In typical
circumstances, best accuracy is achieved when Off Nadir angle is less
than 20 degrees. In these cases, the ground RMSE is within a few meters
[3] . However, the events in Nepal are not considered to by
typical circumstances, and in some cases, we are pushing Off Nadir Angles
above 40 degrees. 
3)  I wanted to confirm that all imagery is
indeed ortho-rectified and geo-corrected to the best of our ability
considering timeliness and the fact many many people and organizations
are waiting for imagery and heavily dependent on its availability. In our
orthorectification process, we are leveraging a variety of elevation
models. Important to note that most elevation models have linear error
that can range from 5-15m. [4] As the off nadir angle
increases, these inaccuracies in the elevation model propagate into
horizontal displacements in the imagery. This is why we are seeing large
offsets. 
4)  The tradeoff here is timely, massive amounts
of post event imagery acquired under less than ideal circumstances
containing horizontal error, or, very limited imagery only collected
under ideal circumstances with minimal horizontal error. As noted below,
typically, the former is preferred. 
 
Hope this helps, Kevin
 
[1] -

https://www.mapbox.com/blog/nepal-imagery-collection/ 
[2] -

http://www.landinfo.com/buying-optical-satellite-imagery-2.html 
[3] -

https://www.digitalglobe.com/sites/default/files/WorldView_Geolocation_Accuracy.pdf
 
[4] -

http://www.satimagingcorp.com/services/orthorectification/ 
 
From: Steve Bower
[
mailto:sbo...@gmavt.net] 
Sent: Thursday, May 07, 2015 10:49 AM
To: Milo van der Linden
Cc: Heather Leson; i...@hotosm.org; Ross Taylor; HOT@OSM
(Humanitarian OpenStreetMap Team)
Subject: Re: [HOT] [info-hotosm] Reference Project #1030 Nepal
Earthquake
 
Springfield,
You raise important points, and are not "raining on a parade".
The resulting data will not be 

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Kevin Bullock]

This is a great thread and I wanted to provide some additional information on 
behalf of DigitalGlobe:


1)  Our goal in collecting imagery and making it available via open license 
is to provide as much data as possible given the humanitarian nature of this 
event. This means we use our satellites in a manner not typically seen. Charlie 
did a great job summarizing this in his recent blog [1]

2)  Given this, we are actually swiveling our satellites to “point” at 
Nepal even when our orbits are not directly over Nepal. As an example, a 
satellite may be vertically overhead Bangladesh, yet, the satellite is looking 
back at Nepal. This is actually quantified and measured in the image metadata 
by referencing the Off Nadir Angle[2] and Target Azimuth. In typical 
circumstances, best accuracy is achieved when Off Nadir angle is less than 20 
degrees. In these cases, the ground RMSE is within a few meters [3] . However, 
the events in Nepal are not considered to by typical circumstances, and in some 
cases, we are pushing Off Nadir Angles above 40 degrees.

3)  I wanted to confirm that all imagery is indeed ortho-rectified and 
geo-corrected to the best of our ability considering timeliness and the fact 
many many people and organizations are waiting for imagery and heavily 
dependent on its availability. In our orthorectification process, we are 
leveraging a variety of elevation models. Important to note that most elevation 
models have linear error that can range from 5-15m. [4] As the off nadir angle 
increases, these inaccuracies in the elevation model propagate into horizontal 
displacements in the imagery. This is why we are seeing large offsets.

4)  The tradeoff here is timely, massive amounts of post event imagery 
acquired under less than ideal circumstances containing horizontal error, or, 
very limited imagery only collected under ideal circumstances with minimal 
horizontal error. As noted below, typically, the former is preferred.

Hope this helps, Kevin

[1] - https://www.mapbox.com/blog/nepal-imagery-collection/
[2] - http://www.landinfo.com/buying-optical-satellite-imagery-2.html
[3] - 
https://www.digitalglobe.com/sites/default/files/WorldView_Geolocation_Accuracy.pdf
[4] - http://www.satimagingcorp.com/services/orthorectification/

From: Steve Bower [mailto:sbo...@gmavt.net]
Sent: Thursday, May 07, 2015 10:49 AM
To: Milo van der Linden
Cc: Heather Leson; i...@hotosm.org; Ross Taylor; HOT@OSM (Humanitarian 
OpenStreetMap Team)
Subject: Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

Springfield,
You raise important points, and are not "raining on a parade". The resulting 
data will not be suitable for all purposes, but it can be very useful for this 
crisis response.

I do think there is significant risk that some mappers will map directly from 
un-rectified imagery, and introduce problematic location errors. That needs to 
be minimized, e.g., through clear instructions and good validation. I think 
there's room for improvement on the instructions, e.g., it would be good to 
have a wiki page on mapping from un-rectified imagery in combination with 
rectified imagery, for crisis response.

Thanks

On Thu, May 7, 2015 at 5:14 AM, Milo van der Linden 
mailto:m...@dogodigi.net>> wrote:
Hello Springfield Harrison,
As a 20 year GIS veteran I understand what you say. I do agree that in 
communication with first responders it is important to have them clearly 
understand that the accuracy of features can be off ~100m. But for them having 
maps that give a good indication is way better then having no maps at all. In 
the end, and that is what I hope for, it can save lives.
I have a long running discussion with y'olde GIS community on "how can a map 
created by amateurs be better then what we professionals do?". It is my opinion 
that it can be. I believe that "the many are smarter than the few" (quote by 
James Surowiecki). And the HOT tasks have all the ingredients to succeed:
1. There is diversity of opinion
2. People involved in the mapping process have opinions not influenced by those 
around them
3. People operate decentralized
The only thing that might need more attention (and this is where geospatial 
experts can take their role) is that HOT and openstreetmap as a whole could use 
more mechanisms to turn all these little "private judgements" into collective 
quality. This process could involve analysing quantity and different 
representations of the same feature through time. In that way, you could see 
the mapping activity (in dense area's) as GPS. There are faults, influenced by 
methodology, opinion and conditions. And as a GPS professional, you know that 
it is _knowing the error_ that automagically creates accuracy. I would love the 
GIS/GPS community to think about how to know the error in community mapping.
I love this new way of mapping. It creates new opportunities. It involves new 
ways

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

Springfield,
You raise important points, and are not "raining on a parade". The
resulting data will not be suitable for all purposes, but it can be very
useful for this crisis response.

I do think there is significant risk that some mappers will map directly
from un-rectified imagery, and introduce problematic location errors. That
needs to be minimized, e.g., through clear instructions and good
validation. I think there's room for improvement on the instructions, e.g.,
it would be good to have a wiki page on mapping from un-rectified imagery
in combination with rectified imagery, for crisis response.

Thanks

On Thu, May 7, 2015 at 5:14 AM, Milo van der Linden 
wrote:

> Hello Springfield Harrison,
>
> As a 20 year GIS veteran I understand what you say. I do agree that in
> communication with first responders it is important to have them clearly
> understand that the accuracy of features can be off ~100m. But for them
> having maps that give a good indication is way better then having no maps
> at all. In the end, and that is what I hope for, it can save lives.
>
> I have a long running discussion with y'olde GIS community on "how can a
> map created by amateurs be better then what we professionals do?". It is my
> opinion that it can be. I believe that "the many are smarter than the few"
> (quote by James Surowiecki). And the HOT tasks have all the ingredients to
> succeed:
>
> 1. There is diversity of opinion
> 2. People involved in the mapping process have opinions not influenced by
> those around them
> 3. People operate decentralized
>
> The only thing that might need more attention (and this is where
> geospatial experts can take their role) is that HOT and openstreetmap as a
> whole could use more mechanisms to turn all these little "private
> judgements" into collective quality. This process could involve analysing
> quantity and different representations of the same feature through time. In
> that way, you could see the mapping activity (in dense area's) as GPS.
> There are faults, influenced by methodology, opinion and conditions. And as
> a GPS professional, you know that it is _knowing the error_ that
> automagically creates accuracy. I would love the GIS/GPS community to think
> about how to know the error in community mapping.
>
> I love this new way of mapping. It creates new opportunities. It involves
> new ways of thinking. It is not influenced by what GIS people say GIS
> should be like.
>
> Kind regards, with respect,
>
> Milo
>
>
> https://en.wikipedia.org/wiki/The_Wisdom_of_Crowds
>
> 2015-05-07 10:21 GMT+02:00 Springfield Harrison :
>
>>  Hello Steve,
>>
>> Sorry to rain on the parade yet again but I find this matter of
>> image alignment to be puzzling and concerning.
>>
>> One of the first things I learned when embarking upon GIS/GPS
>> mapping was that accurate georeferencing of all layers, but especially the
>> base layers (imagery in this case) was sacrosanct.  If things are not in
>> their correct point in space, what use is that to the end user?  Especially
>> in rugged terrain, with difficult access and rapidly changing stream flows,
>> it is important to know where a trail or road really is.  Why try to cross
>> a raging torrent when you don't need to?
>>
>> Having untrained users realign the imagery willy-nilly is
>> amazing to me.  What faith can anyone have in the new tracings if the earth
>> is literally moving every time a new user opens up the file?  Accurate map
>> datums and projections were created for a reason.
>>
>> How is it that, "...the DigitalGlobe 2015-05-03 (DG) images have
>> had minimal georectification.."  This is bizarre, this is not GIS, this is
>> merely sketching.  Why is such imagery being offered and accepted?  I know
>> that this is a major emergency but then all the more need for quality data.
>>
>> However, I am newly arrived, and it seems that most people are
>> content with a world that can be up to 200 m out of whack.  I'm not sure if
>> I can contribute much under the circumstances other than this gloomy
>> criticism.  Sorry, will try not to dampen the enthusiasm further.
>>
>>  Thanks for your patience, Cheers . . . . . . . . Spring
>>
>>
>>
>> At 06-05-2015 11:59 Wednesday, Steve Bower wrote:
>>
>> Ross - If you haven't already, see the recent threads on "data alignment
>> to satellite imagery" and "imagery alignment", in the archives for May:
>>  https://lists.openstreetmap.org/pipermail/hot/2015-May/thread.htmlÂ
>>
>> Note some links pointed out there by althio:
>> Â http://wiki.openstreetmap.org/wiki/Using_ImageryÂ
>> Â http://learnosm.org/en/editing/correcting-imagery-offset/Â
>>
>> Because the DigitalGlobe 2015-05-03 (DG) images have had minimal
>> georectification (needed mainly for elevation distortion), they may be
>> offset by 100m or more. On one tile (5.5km wide) I saw offsets relative to
>> Bing of 125m to the west and, elsewhere, 85m to the east. The offsets may
>> vary c

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Milo van der Linden]

Hello Springfield Harrison,

As a 20 year GIS veteran I understand what you say. I do agree that in
communication with first responders it is important to have them clearly
understand that the accuracy of features can be off ~100m. But for them
having maps that give a good indication is way better then having no maps
at all. In the end, and that is what I hope for, it can save lives.

I have a long running discussion with y'olde GIS community on "how can a
map created by amateurs be better then what we professionals do?". It is my
opinion that it can be. I believe that "the many are smarter than the few"
(quote by James Surowiecki). And the HOT tasks have all the ingredients to
succeed:

1. There is diversity of opinion
2. People involved in the mapping process have opinions not influenced by
those around them
3. People operate decentralized

The only thing that might need more attention (and this is where geospatial
experts can take their role) is that HOT and openstreetmap as a whole could
use more mechanisms to turn all these little "private judgements" into
collective quality. This process could involve analysing quantity and
different representations of the same feature through time. In that way,
you could see the mapping activity (in dense area's) as GPS. There are
faults, influenced by methodology, opinion and conditions. And as a GPS
professional, you know that it is _knowing the error_ that automagically
creates accuracy. I would love the GIS/GPS community to think about how to
know the error in community mapping.

I love this new way of mapping. It creates new opportunities. It involves
new ways of thinking. It is not influenced by what GIS people say GIS
should be like.

Kind regards, with respect,

Milo


https://en.wikipedia.org/wiki/The_Wisdom_of_Crowds

2015-05-07 10:21 GMT+02:00 Springfield Harrison :

>  Hello Steve,
>
> Sorry to rain on the parade yet again but I find this matter of
> image alignment to be puzzling and concerning.
>
> One of the first things I learned when embarking upon GIS/GPS
> mapping was that accurate georeferencing of all layers, but especially the
> base layers (imagery in this case) was sacrosanct.  If things are not in
> their correct point in space, what use is that to the end user?  Especially
> in rugged terrain, with difficult access and rapidly changing stream flows,
> it is important to know where a trail or road really is.  Why try to cross
> a raging torrent when you don't need to?
>
> Having untrained users realign the imagery willy-nilly is amazing
> to me.  What faith can anyone have in the new tracings if the earth is
> literally moving every time a new user opens up the file?  Accurate map
> datums and projections were created for a reason.
>
> How is it that, "...the DigitalGlobe 2015-05-03 (DG) images have
> had minimal georectification.."  This is bizarre, this is not GIS, this is
> merely sketching.  Why is such imagery being offered and accepted?  I know
> that this is a major emergency but then all the more need for quality data.
>
> However, I am newly arrived, and it seems that most people are
> content with a world that can be up to 200 m out of whack.  I'm not sure if
> I can contribute much under the circumstances other than this gloomy
> criticism.  Sorry, will try not to dampen the enthusiasm further.
>
>  Thanks for your patience, Cheers . . . . . . . . Spring
>
>
>
> At 06-05-2015 11:59 Wednesday, Steve Bower wrote:
>
> Ross - If you haven't already, see the recent threads on "data alignment
> to satellite imagery" and "imagery alignment", in the archives for May:
>  https://lists.openstreetmap.org/pipermail/hot/2015-May/thread.htmlÂ
>
> Note some links pointed out there by althio:
> Â http://wiki.openstreetmap.org/wiki/Using_ImageryÂ
> Â http://learnosm.org/en/editing/correcting-imagery-offset/Â
>
> Because the DigitalGlobe 2015-05-03 (DG) images have had minimal
> georectification (needed mainly for elevation distortion), they may be
> offset by 100m or more. On one tile (5.5km wide) I saw offsets relative to
> Bing of 125m to the west and, elsewhere, 85m to the east. The offsets may
> vary considerable even in nearby areas, especially in steep terrain.Â
>
> You should align your work with Bing imagery. Thus to digitize from the DG
> imagery you should first adjust the DG imagery to the Bing imagery, and
> re-adjust it as you move from place to place. As you noted, adjusting in
> one area makes it worse in others, so you have to keep re-adjusting as you
> go. You should be able to compare the Bing and DG imagery to confirm where
> a feature visible on DG is located on the Bing imagery (if Bing is clear
> enough). I try to adjust based on buildings, or road intersections/curves
> (keeping in mind that roads are sometimes relocated), or even less
> permanent features (rivers generally are not good, they move around to
> much). It's a time-consuming process, but needed to correctly

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[althio]

On 7 May 2015 at 10:21, Springfield Harrison  wrote:
> Having untrained users realign the imagery willy-nilly is amazing to me.

Usually we don't.

This is crisis response and hence crisis-GIS.
We are striving to produce useful and good enough data, not perfect data.
We are working with multiple passes to improve gradually.

Typically we split users:
Basemap for everyone
- with correctly georeferenced imagery (Bing), not up-to-date
- with standard tagging, included in iD presets
Specialists tasks for experienced OSM/GIS users
- with cutting-edge imagery
- with somewhat innovative or custom tagging


> How is it that, "...the DigitalGlobe 2015-05-03 (DG) images have had
> minimal georectification.."  This is bizarre, this is not GIS, this is
> merely sketching.  Why is such imagery being offered and accepted?

Because this imagery is: first, only, available, best, useful and
directly put to use.


> it seems that most people are content with a world that can be up to 200 m 
> out of whack.

We are not.

___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Springfield Harrison]

Hello Steve,
Sorry to
rain on the parade yet again but I find this matter of image alignment to
be puzzling and concerning.
One of the
first things I learned when embarking upon GIS/GPS mapping was that
accurate georeferencing of all layers, but especially the base layers
(imagery in this case) was sacrosanct.  If things are not in their
correct point in space, what use is that to the end user? 
Especially in rugged terrain, with difficult access and rapidly changing
stream flows, it is important to know where a trail or road really
is.  Why try to cross a raging torrent when you don't need
to?
Having
untrained users realign the imagery willy-nilly is amazing to me. 
What faith can anyone have in the new tracings if the earth is literally
moving every time a new user opens up the file?  Accurate map datums
and projections were created for a reason.
How is it
that, "...the DigitalGlobe 2015-05-03 (DG) images have had
minimal georectification.."  This is bizarre, this is not GIS,
this is merely sketching.  Why is such imagery being offered and
accepted?  I know that this is a major emergency but then all the
more need for quality data.
However, I
am newly arrived, and it seems that most people are content with a world
that can be up to 200 m out of whack.  I'm not sure if I can
contribute much under the circumstances other than this gloomy
criticism.  Sorry, will try not to dampen the enthusiasm
further.

Thanks for your
patience, Cheers . . . . . . . . Spring

At 06-05-2015 11:59 Wednesday, Steve Bower wrote:
Ross - If you haven't already,
see the recent threads on "data alignment to satellite imagery"
and "imagery alignment", in the archives for May:

https://lists.openstreetmap.org/pipermail/hot/2015-May/thread.htmlÂ

Note some links pointed out there by althio:
 

http://wiki.openstreetmap.org/wiki/Using_Imagery 
 

http://learnosm.org/en/editing/correcting-imagery-offset/Â 
Because the DigitalGlobe 2015-05-03 (DG) images have had minimal
georectification (needed mainly for elevation distortion), they may be
offset by 100m or more. On one tile (5.5km wide) I saw offsets relative
to Bing of 125m to the west and, elsewhere, 85m to the east. The offsets
may vary considerable even in nearby areas, especially in steep terrain.Â

You should align your work with Bing imagery. Thus to digitize from the
DG imagery you should first adjust the DG imagery to the Bing imagery,
and re-adjust it as you move from place to place. As you noted, adjusting
in one area makes it worse in others, so you have to keep re-adjusting as
you go. You should be able to compare the Bing and DG imagery to confirm
where a feature visible on DG is located on the Bing imagery (if Bing is
clear enough). I try to adjust based on buildings, or road
intersections/curves (keeping in mind that roads are sometimes
relocated), or even less permanent features (rivers generally are not
good, they move around to much). It's a time-consuming process, but
needed to correctly locate features.
It's not essential that everything be within a few meters of its true
location, but features should be mapped correctly relative to
one-another.
The links above provide guidance on how to align imagery to correct
locations. It's easy in JOSM with the Imagery Offset tool (on the
toolbar).
Steve
On Wed, May 6, 2015 at 1:53 PM, Steve Bower

wrote:


I don't think Chad's IDP guidance document (though very helpful)
addresses the issue of spatial accuracy of the DG imagery, raised by
Ross. I'm going to post that as a separate issue with more
detail.

On Wed, May 6, 2015 at 4:35 AM, Heather Leson
 wrote:


HI Ross, sorry for my delayed response. It is best if you ask your
questions on the main
Hot@openstreetmap.org mailing
list. 

Chad provided this guidance document on IDPs 

http://hotosm.github.io/tracing-guides/guide/Nepal.html#IDP%20Collection%20Guidance


Hope this helps

Heather 

On Tue, May 5, 2015 at 12:40 AM, Ross Taylor
 wrote:


Hi, I am seeing many more IDP sites using DigitlaGlobe imagery vs
Bing. I can toggle between the two image sets, but they are significantly
nonaligned. I created a landuse=brownfield tagged area which aligns with
Bing, but if I mark and tag the individual IDP sites showing up in
DigitalGlobe imagery, the brownfield and idp are not going to be
aligned.  I want to help out as much as possible and would like the data
to be correct. Please advise, thanks!

Note: I tried to adjust alignment but it fixes one area and creates
more offset in other areas.

-Ross

Sent from mobile



___

HOT mailing list

HOT@openstreetmap.org



https://lists.openstreetmap.org/listinfo/hot




___ HOT mailing list
HOT@openstreetmap.org

https://lists.openstreetmap.org/listinfo/hot 



___
HOT mai

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

Ross - If you haven't already, see the recent threads on "data alignment to
satellite imagery" and "imagery alignment", in the archives for May:
https://lists.openstreetmap.org/pipermail/hot/2015-May/thread.html

Note some links pointed out there by althio:
  http://wiki.openstreetmap.org/wiki/Using_Imagery
  http://learnosm.org/en/editing/correcting-imagery-offset/

Because the DigitalGlobe 2015-05-03 (DG) images have had minimal
georectification (needed mainly for elevation distortion), they may be
offset by 100m or more. On one tile (5.5km wide) I saw offsets relative to
Bing of 125m to the west and, elsewhere, 85m to the east. The offsets may
vary considerable even in nearby areas, especially in steep terrain.

You should align your work with Bing imagery. Thus to digitize from the DG
imagery you should first adjust the DG imagery to the Bing imagery, and
re-adjust it as you move from place to place. As you noted, adjusting in
one area makes it worse in others, so you have to keep re-adjusting as you
go. You should be able to compare the Bing and DG imagery to confirm where
a feature visible on DG is located on the Bing imagery (if Bing is clear
enough). I try to adjust based on buildings, or road intersections/curves
(keeping in mind that roads are sometimes relocated), or even less
permanent features (rivers generally are not good, they move around to
much). It's a time-consuming process, but needed to correctly locate
features.

It's not essential that everything be within a few meters of its true
location, but features should be mapped correctly relative to one-another.

The links above provide guidance on how to align imagery to correct
locations. It's easy in JOSM with the Imagery Offset tool (on the toolbar).

Steve

On Wed, May 6, 2015 at 1:53 PM, Steve Bower  wrote:

> I don't think Chad's IDP guidance document (though very helpful) addresses
> the issue of spatial accuracy of the DG imagery, raised by Ross. I'm going
> to post that as a separate issue with more detail.
>
> On Wed, May 6, 2015 at 4:35 AM, Heather Leson 
> wrote:
>
>> HI Ross, sorry for my delayed response. It is best if you ask your
>> questions on the main Hot@openstreetmap.org mailing list.
>>
>> Chad provided this guidance document on IDPs
>> http://hotosm.github.io/tracing-guides/guide/Nepal.html#IDP%20Collection%20Guidance
>>
>> Hope this helps
>>
>> Heather
>>
>> On Tue, May 5, 2015 at 12:40 AM, Ross Taylor 
>> wrote:
>>
>>> Hi, I am seeing many more IDP sites using DigitlaGlobe imagery vs Bing.
>>> I can toggle between the two image sets, but they are significantly
>>> nonaligned. I created a landuse=brownfield tagged area which aligns with
>>> Bing, but if I mark and tag the individual IDP sites showing up in
>>> DigitalGlobe imagery, the brownfield and idp are not going to be aligned.
>>> I want to help out as much as possible and would like the data to be
>>> correct. Please advise, thanks!
>>>
>>> Note: I tried to adjust alignment but it fixes one area and creates more
>>> offset in other areas.
>>>
>>> -Ross
>>>
>>> Sent from mobile
>>
>>
>>
>> ___
>> HOT mailing list
>> HOT@openstreetmap.org
>> https://lists.openstreetmap.org/listinfo/hot
>>
>>
>
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Steve Bower]

I don't think Chad's IDP guidance document (though very helpful) addresses
the issue of spatial accuracy of the DG imagery, raised by Ross. I'm going
to post that as a separate issue with more detail.

On Wed, May 6, 2015 at 4:35 AM, Heather Leson 
wrote:

> HI Ross, sorry for my delayed response. It is best if you ask your
> questions on the main Hot@openstreetmap.org mailing list.
>
> Chad provided this guidance document on IDPs
> http://hotosm.github.io/tracing-guides/guide/Nepal.html#IDP%20Collection%20Guidance
>
> Hope this helps
>
> Heather
>
> On Tue, May 5, 2015 at 12:40 AM, Ross Taylor 
> wrote:
>
>> Hi, I am seeing many more IDP sites using DigitlaGlobe imagery vs Bing. I
>> can toggle between the two image sets, but they are significantly
>> nonaligned. I created a landuse=brownfield tagged area which aligns with
>> Bing, but if I mark and tag the individual IDP sites showing up in
>> DigitalGlobe imagery, the brownfield and idp are not going to be aligned.
>> I want to help out as much as possible and would like the data to be
>> correct. Please advise, thanks!
>>
>> Note: I tried to adjust alignment but it fixes one area and creates more
>> offset in other areas.
>>
>> -Ross
>>
>> Sent from mobile
>
>
>
> ___
> HOT mailing list
> HOT@openstreetmap.org
> https://lists.openstreetmap.org/listinfo/hot
>
>
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot

Re: [HOT] [info-hotosm] Reference Project #1030 Nepal Earthquake

[Heather Leson]

HI Ross, sorry for my delayed response. It is best if you ask your
questions on the main Hot@openstreetmap.org mailing list.

Chad provided this guidance document on IDPs
http://hotosm.github.io/tracing-guides/guide/Nepal.html#IDP%20Collection%20Guidance

Hope this helps

Heather

On Tue, May 5, 2015 at 12:40 AM, Ross Taylor 
wrote:

> Hi, I am seeing many more IDP sites using DigitlaGlobe imagery vs Bing. I
> can toggle between the two image sets, but they are significantly
> nonaligned. I created a landuse=brownfield tagged area which aligns with
> Bing, but if I mark and tag the individual IDP sites showing up in
> DigitalGlobe imagery, the brownfield and idp are not going to be aligned.
> I want to help out as much as possible and would like the data to be
> correct. Please advise, thanks!
>
> Note: I tried to adjust alignment but it fixes one area and creates more
> offset in other areas.
>
> -Ross
>
> Sent from mobile
___
HOT mailing list
HOT@openstreetmap.org
https://lists.openstreetmap.org/listinfo/hot