Re: [Talk-GB] Aerial Photography

[Chris Hill]

Peter Miller wrote:
> I get the impression that rectification gets a lot harder as the angle 
> gets more slight and it is clear to me that a camera pointing straight 
> down would be the most useful device going forward.
Not easy to do.  You can't legally modify an aircraft at all without 
invalidating its certificate of airworthiness, so where to mount the 
camera?
> The time of day is also important to avoid long shadows.
Generally an overcast day reduces the contrast to make the photos easier 
to use, but shadows can actually be very helpful.  They give an 
impression of height for some things.  For archeology shadows sometimes 
showed medieval ridge and furrow field systems and the edges of roman 
building platforms.  Winter time when there are no leaves on the trees 
will reveal much more detail.  The true route of roads and streams are 
easily hidden by tree cover from the air.  Calm winter days often are 
less turbulent than summer days so the 'plane as a platform is 
steadier.  (Clear blue skies in summer can be VERY bumpy in the air).
> I am pleased that this project is creating some useful discussion 
> which we should continue to see what we can extract from these images 
> and what we can learn going forward.
>
> Tools to process images and to host rectified images seem to be pretty 
> crucial to take full advantage of all this.
>
> Fyi, I have added comments to some images to say what it is of, the 
> bearing the image was taken at, and the appropriate link to OSM.


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Re: [Talk-GB] Aerial Photography

[Lennard]

Jack Stringer wrote:

> I would take the assumption they were using a medium format digital
> camera such as a Hasselblad. If I was going to take quality pictures
> of the ground from a plane I would want to use medium format as that
> would give high resolution images.

Although in Dutch, this pdf[1] offers some hints:

Cameras: Large format digital photogrammetric cameras, gyro-stabilised 
mounting ring, forward motion compensation

Stereometric photography:

Resolution: 10 cm (+/- 10%)
Longitudinal overlap: 60%
Lateral overlap: 25%
Spectral bands: colour (24 bit RGB)
Data volume: 600MB per exposure, 17310 x 11310 pixels

Orthorectified photography:

Data volume: 300MB/km^2 uncompressed


[1] 

-- 
Lennard

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Re: [Talk-GB] Aerial Photography

[Jack Stringer]

2009/9/14 Chris Hill :
> One of the airfields I flew from was a base for the OS photo surveying
> unit.  They had a 'plane which had been modified to have a downward
> pointing, very expensive camera built into the fuselage.  They could
> then fly long straight strips, taking overlapping photos and then taking
> overlapping strips.  The pilots didn't stay long - it was a very
> difficult and tedious job getting the strips to line up.  They flew a
> few in a day, always in the same direction to assist with the way your
> track gets moved by the wind.

I would take the assumption they were using a medium format digital
camera such as a Hasselblad. If I was going to take quality pictures
of the ground from a plane I would want to use medium format as that
would give high resolution images.


Jack Stringer

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Re: [Talk-GB] Aerial Photography

[Chris Hill]

One of the airfields I flew from was a base for the OS photo surveying 
unit.  They had a 'plane which had been modified to have a downward 
pointing, very expensive camera built into the fuselage.  They could 
then fly long straight strips, taking overlapping photos and then taking 
overlapping strips.  The pilots didn't stay long - it was a very 
difficult and tedious job getting the strips to line up.  They flew a 
few in a day, always in the same direction to assist with the way your 
track gets moved by the wind. 

Cheers, Chris

John Robert Peterson wrote:
> Part of the idea of this project was to kick start thinking about this 
> sort of thing.
>
> The ideal situation for me would be if we could have some automated 
> tool on a sever somewhere receiving images from users, and 
> automatically rectifying them.
>
> This sounds imposable, but I believe that with a very small amount of 
> user help it could work:
> Images can be automatically pinned together in overlaps (and high res 
> images can be pinned onto wide area images) using tools similar to 
> those in Panorama Tools / hugin (this searches for notable points in 
> the image data, and matches them between images);
> searching the images for road markings (and/or cars) and matching 
> these to the gps traces already uploaded would give a reliable enough 
> way to add real world control points;
> if a concept of altitude is added, automatic control points between 
> images appearing on top of skyscrapers would not be too damaging;
> approximate terrain relief for most of the planet is already known, 
> this can be tied into the above to help;
> manually adding control points would be done by displaying already 
> rectified images next to a map, with the user adding pins to useful 
> points;
> images with no rectification data at all would be added using a push 
> pin system similar to that used on http://warper.geothings.net/
>
> the above is a pipe dream at the moment, but has the potential to 
> revolutionise how we do things in my opinion.
>
> Any further ideas on this?
>
> The images of stratford were taken mostly angled, with a few almost 
> vertical. we spiraled around the town and I took images out the 
> downward facing window, it seemed to work pretty well (if the results 
> are a little chaotic)
>
> mapping from these images is the million dollar question -- the raw 
> images are going up online at 
> http://www.flickr.com/photos/thingomy/collections/72157622345143470/ 
> and are fine for visual reference while mapping, but rectifying them 
> is a more tricky issue.
>
> JR
>
>
> 2009/9/14 Tristan Thomas  >
>
>
> Many of the photos taken above Stratford upon Avon seem to be
> taken at an angle-how do people find them for mapping from?
>
>  
> 2009/9/14 Chris Hill mailto:o...@raggedred.net>>
>
> I used to hold a pilot's licence and I did some work
> photographing archaeological sites.  Photos taken pointing
> sideways are much harder to work with than photos pointing
> straight down. Any kind of rectification adds unwanted
> artifacts.  I used to make high bank angle turns (60' bank
> angle) over the feature I wanted to photograph which made it
> very easy to photograph.
>
> I was trying to photograph a small area in detail, so circling
> over the feature helped.  I was also using film (before
> widespread hi-res digital), so there was a limited stock of
> film but the resulting image was the equivalent of about 25mp.
>  To reduce parallax I used a telephoto lens.
>
> It gives a very interesting overview, but it's not a patch on
> surveying on the ground where you have access.
>
> Cheers, Chris
>
> Tristan Thomas wrote:
>
> I would be very interested to hear what people think of
> this effort.  I'm currently studying to be a pilot & I
> know that many people who do fly routinely take aerial
> pictures of the landscape below, especially of towns etc.
>  I know most of them would be more than happy to allow
> their photos to be used of OSM.  If we could find a way to
> upload them somewhere, then I'm sure we could dramatically
> increase the aerial photography we have without having to
> pay to hire the planes or get it sponsored.  I could just
> upload them all under one Flickr account for OSMers to
> look through & do some tracing if they wish, but it
> doesn't seem the most efficient way to do it?
>  Thoughts?
> 
> 
>
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Re: [Talk-GB] Aerial Photography

[Peter Miller]

On 14 Sep 2009, at 11:57, John Robert Peterson wrote:

Part of the idea of this project was to kick start thinking about  
this sort of thing.


The ideal situation for me would be if we could have some automated  
tool on a sever somewhere receiving images from users, and  
automatically rectifying them.


This sounds imposable, but I believe that with a very small amount  
of user help it could work:
Images can be automatically pinned together in overlaps (and high  
res images can be pinned onto wide area images) using tools similar  
to those in Panorama Tools / hugin (this searches for notable points  
in the image data, and matches them between images);
searching the images for road markings (and/or cars) and matching  
these to the gps traces already uploaded would give a reliable  
enough way to add real world control points;
if a concept of altitude is added, automatic control points between  
images appearing on top of skyscrapers would not be too damaging;
approximate terrain relief for most of the planet is already known,  
this can be tied into the above to help;
manually adding control points would be done by displaying already  
rectified images next to a map, with the user adding pins to useful  
points;
images with no rectification data at all would be added using a push  
pin system similar to that used on http://warper.geothings.net/


the above is a pipe dream at the moment, but has the potential to  
revolutionise how we do things in my opinion.


Any further ideas on this?

The images of stratford were taken mostly angled, with a few almost  
vertical. we spiraled around the town and I took images out the  
downward facing window, it seemed to work pretty well (if the  
results are a little chaotic)


mapping from these images is the million dollar question -- the raw  
images are going up online at http://www.flickr.com/photos/thingomy/collections/72157622345143470/ 
 and are fine for visual reference while mapping, but rectifying  
them is a more tricky issue.


I get the impression that rectification gets a lot harder as the angle  
gets more slight and it is clear to me that a camera pointing straight  
down would be the most useful device going forward. The time of day is  
also important to avoid long shadows. I am pleased that this project  
is creating some useful discussion which we should continue to see  
what we can extract from these images and what we can learn going  
forward.


Tools to process images and to host rectified images seem to be pretty  
crucial to take full advantage of all this.


Fyi, I have added comments to some images to say what it is of, the  
bearing the image was taken at, and the appropriate link to OSM.




Regards,


Peter




JR


2009/9/14 Tristan Thomas 

Many of the photos taken above Stratford upon Avon seem to be taken  
at an angle-how do people find them for mapping from?



2009/9/14 Chris Hill 

I used to hold a pilot's licence and I did some work photographing  
archaeological sites.  Photos taken pointing sideways are much  
harder to work with than photos pointing straight down. Any kind of  
rectification adds unwanted artifacts.  I used to make high bank  
angle turns (60' bank angle) over the feature I wanted to photograph  
which made it very easy to photograph.


I was trying to photograph a small area in detail, so circling over  
the feature helped.  I was also using film (before widespread hi-res  
digital), so there was a limited stock of film but the resulting  
image was the equivalent of about 25mp.  To reduce parallax I used a  
telephoto lens.


It gives a very interesting overview, but it's not a patch on  
surveying on the ground where you have access.


Cheers, Chris

Tristan Thomas wrote:
I would be very interested to hear what people think of this  
effort.  I'm currently studying to be a pilot & I know that many  
people who do fly routinely take aerial pictures of the landscape  
below, especially of towns etc.  I know most of them would be more  
than happy to allow their photos to be used of OSM.  If we could  
find a way to upload them somewhere, then I'm sure we could  
dramatically increase the aerial photography we have without having  
to pay to hire the planes or get it sponsored.  I could just upload  
them all under one Flickr account for OSMers to look through & do  
some tracing if they wish, but it doesn't seem the most efficient  
way to do it?

 Thoughts?


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Re: [Talk-GB] Aerial Photography

[John Robert Peterson]

Part of the idea of this project was to kick start thinking about this sort
of thing.

The ideal situation for me would be if we could have some automated tool on
a sever somewhere receiving images from users, and automatically rectifying
them.

This sounds imposable, but I believe that with a very small amount of user
help it could work:
Images can be automatically pinned together in overlaps (and high res images
can be pinned onto wide area images) using tools similar to those in
Panorama Tools / hugin (this searches for notable points in the image data,
and matches them between images);
searching the images for road markings (and/or cars) and matching these to
the gps traces already uploaded would give a reliable enough way to add real
world control points;
if a concept of altitude is added, automatic control points between images
appearing on top of skyscrapers would not be too damaging;
approximate terrain relief for most of the planet is already known, this can
be tied into the above to help;
manually adding control points would be done by displaying already rectified
images next to a map, with the user adding pins to useful points;
images with no rectification data at all would be added using a push pin
system similar to that used on http://warper.geothings.net/

the above is a pipe dream at the moment, but has the potential to
revolutionise how we do things in my opinion.

Any further ideas on this?

The images of stratford were taken mostly angled, with a few almost
vertical. we spiraled around the town and I took images out the downward
facing window, it seemed to work pretty well (if the results are a little
chaotic)

mapping from these images is the million dollar question -- the raw images
are going up online at
http://www.flickr.com/photos/thingomy/collections/72157622345143470/ and are
fine for visual reference while mapping, but rectifying them is a more
tricky issue.

JR


2009/9/14 Tristan Thomas 

>
> Many of the photos taken above Stratford upon Avon seem to be taken at an
> angle-how do people find them for mapping from?
>
>
> 2009/9/14 Chris Hill 
>
> I used to hold a pilot's licence and I did some work photographing
>> archaeological sites.  Photos taken pointing sideways are much harder to
>> work with than photos pointing straight down. Any kind of rectification adds
>> unwanted artifacts.  I used to make high bank angle turns (60' bank angle)
>> over the feature I wanted to photograph which made it very easy to
>> photograph.
>>
>> I was trying to photograph a small area in detail, so circling over the
>> feature helped.  I was also using film (before widespread hi-res digital),
>> so there was a limited stock of film but the resulting image was the
>> equivalent of about 25mp.  To reduce parallax I used a telephoto lens.
>>
>> It gives a very interesting overview, but it's not a patch on surveying on
>> the ground where you have access.
>>
>> Cheers, Chris
>>
>> Tristan Thomas wrote:
>>
>>> I would be very interested to hear what people think of this effort.  I'm
>>> currently studying to be a pilot & I know that many people who do fly
>>> routinely take aerial pictures of the landscape below, especially of towns
>>> etc.  I know most of them would be more than happy to allow their photos to
>>> be used of OSM.  If we could find a way to upload them somewhere, then I'm
>>> sure we could dramatically increase the aerial photography we have without
>>> having to pay to hire the planes or get it sponsored.  I could just upload
>>> them all under one Flickr account for OSMers to look through & do some
>>> tracing if they wish, but it doesn't seem the most efficient way to do it?
>>>  Thoughts?
>>> 
>>>
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>>
>>
>
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Re: [Talk-GB] Aerial Photography

[Tristan Thomas]

Many of the photos taken above Stratford upon Avon seem to be taken at an
angle-how do people find them for mapping from?


2009/9/14 Chris Hill 

> I used to hold a pilot's licence and I did some work photographing
> archaeological sites.  Photos taken pointing sideways are much harder to
> work with than photos pointing straight down. Any kind of rectification adds
> unwanted artifacts.  I used to make high bank angle turns (60' bank angle)
> over the feature I wanted to photograph which made it very easy to
> photograph.
>
> I was trying to photograph a small area in detail, so circling over the
> feature helped.  I was also using film (before widespread hi-res digital),
> so there was a limited stock of film but the resulting image was the
> equivalent of about 25mp.  To reduce parallax I used a telephoto lens.
>
> It gives a very interesting overview, but it's not a patch on surveying on
> the ground where you have access.
>
> Cheers, Chris
>
> Tristan Thomas wrote:
>
>> I would be very interested to hear what people think of this effort.  I'm
>> currently studying to be a pilot & I know that many people who do fly
>> routinely take aerial pictures of the landscape below, especially of towns
>> etc.  I know most of them would be more than happy to allow their photos to
>> be used of OSM.  If we could find a way to upload them somewhere, then I'm
>> sure we could dramatically increase the aerial photography we have without
>> having to pay to hire the planes or get it sponsored.  I could just upload
>> them all under one Flickr account for OSMers to look through & do some
>> tracing if they wish, but it doesn't seem the most efficient way to do it?
>>  Thoughts?
>> 
>>
>> ___
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>>
>>
>
>
>
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Re: [Talk-GB] Aerial Photography

[Chris Hill]

I used to hold a pilot's licence and I did some work photographing 
archaeological sites.  Photos taken pointing sideways are much harder to 
work with than photos pointing straight down. Any kind of rectification 
adds unwanted artifacts.  I used to make high bank angle turns (60' bank 
angle) over the feature I wanted to photograph which made it very easy 
to photograph.

I was trying to photograph a small area in detail, so circling over the 
feature helped.  I was also using film (before widespread hi-res 
digital), so there was a limited stock of film but the resulting image 
was the equivalent of about 25mp.  To reduce parallax I used a telephoto 
lens.

It gives a very interesting overview, but it's not a patch on surveying 
on the ground where you have access.

Cheers, Chris

Tristan Thomas wrote:
> I would be very interested to hear what people think of this effort.  
> I'm currently studying to be a pilot & I know that many people who do 
> fly routinely take aerial pictures of the landscape below, especially 
> of towns etc.  I know most of them would be more than happy to allow 
> their photos to be used of OSM.  If we could find a way to upload them 
> somewhere, then I'm sure we could dramatically increase the aerial 
> photography we have without having to pay to hire the planes or get it 
> sponsored.  I could just upload them all under one Flickr account for 
> OSMers to look through & do some tracing if they wish, but it doesn't 
> seem the most efficient way to do it?
>  
> Thoughts?
> 
>
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