Re: [Tagging] Accuracy of survey

[André Pirard]

  
  
Accuracy is indeed a problem.
  An early OSM update I made was moving a borderline by 250m and put
  a devotion site from an arrondissement to another.
  Since then many corrections of more that 5 m, mainly due to user
  being unaware of Bing's offset (at close zoom of course, in some
  places only, poisoned gift) and some editors.
  I just checked a place where I had spotted a Bing offset before. 
  National aerial photos 2009 and 2012 were offset by 2.8m. Bing was
  almost in the middle 
  Smart phones have a bad accuracy reputation. I have however bought
  one based on a "good GPS" user report and, indeed I verified quick
  fix and immediate 4m accuracy by cloudy weather in a veranda.
  Former one around 10m and couldn't fix in house.
  
  On 2014-12-23 18:49, Malcolm Herring wrote :

On
  23/12/2014 16:57, Tom Pfeifer wrote:
  
  The collection of

   traces over a longer time creates a cloud of traces which

   form a Gaussian bell curve, in density, over the ground
truth.

  
  
  Except that the position of a node in the DB is the last edited
  value, not the mean position of all historical values.
  

Yet, I sketched a funny program that analyzes a GPX trace,
determines when the car stops (I doubt it could work for foot),
takes the mean value of the wandering position until the car moves
again, and creates a POI for JOSM to layer.
The results were surprising for an alpha 0 pre-release pure hack. 
After rolling up one's sleeves higher, one could imagine processing
several traces, such as ones recorded by buses to determine the
coordinates of the stops. 
I had been surprised by how much the GPX position moves about when
the GPS is stopped (compared to when it moves) and I will test that
with my new smartphone when better weather returns.

Cheers



  

  André.

  



  


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Re: [Tagging] Accuracy of survey

[André Pirard]

  
  
Oops, I forgot to finish a phrase...
  I just checked a place where I had spotted a Bing offset before
  and that disappeared.  National aerial photos 2009 and 2012 are
  offset by 2.8m. Bing is almost in the middle. But that's because
  of a perspective effect. The national orthos have house walls
  slanted by about 1.4 m for the house height and 2009 and 2012 are
  slanted in opposite directions. The roofs are offset but they are
  at the same position at ground level. That's of course very tricky
  to compensate if one maps house based on roof contours. 


Cheers 


  

  André.

  



  


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Re: [Tagging] Distinction between amenity=restaurant and fast_food

[Bryce Nesbitt]

While all restaurants pre-cook some food,
fast food restaurants often cook the majority of food prior to
a customer order.

But there's just simply no firm line between restaurant and fast food.
But there are lots of attributes:

does it serve food?
does it serve alcohol?
how fast is food available after ordering?
is it table service with waiters?
is it counter service with tables?
is takeout available?
is there drive thru takeout?
is there a restroom amenity?
is there a playground amenity?
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Re: [Tagging] Accuracy of survey

[Tom Pfeifer]

Friedrich Volkmann wrote on 2014-12-23 23:59:


There are no GPS traces for pipeline markes. There are traces for roads and
paths only.


It was not clear if the OP indeed wants to map pipelines,
or was just quoting the pipeline expert for his opinion about
surveying methods. And if you walk/drive along the pipeline, you
could create a trace, and even repeat over time.


These traces can bear a systematic error due to reflections
(e.g. under a cliff).


Yes of course, and in an "urban canyon" our multi-trace bell curve would be
very flat due to the even larger amount of multipath reception
and the position noise it injects.


Even if you collect plenty of GPS traces with no systematic error, these
still cannot beat a theodolite triangulation.


I tend to agree on the practical side, although triangulation has error
sources too, and we haven't defined the scale of your experiment, and the
number of my traces, for the scientific comparison. ;-)

My main argument, if you read it in context, was that crowdsourcing
of traces from consumer-grade devices provides a significant statistical
advantage over a single trace of such, an effect that the pipeline expert
might not have been aware of.

tom



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Re: [Tagging] Tagging Digest, Vol 63, Issue 72

[Ulrich Lamm]

Some weeks ago, I have written something on reliable mapping, see 
https://wiki.openstreetmap.org/wiki/User:Ulamm/Mappers,_evaluators_and_feedback

For a special feature, I'd also added it to an existing article, but it was 
reverted, see "Attention" in the upper table of 
https://wiki.openstreetmap.org/w/index.php?title=Tag:bicycle%3Duse_sidepath&oldid=1119074

Ulrich


Am 24.12.2014 um 01:29 schrieb tagging-requ...@openstreetmap.org:

> Date: Tue, 23 Dec 2014 17:37:34 +0100
> From: Rainer Fügenstein 
> To: "Tag discussion, strategy and related tools"
>   
> Subject: [Tagging] Accuracy of survey
> Message-ID: <811143140.20141223173...@oudeis.org>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> 
> while we are at it, imagine the following situation:
> 
> mapper A, by means of DGPS, MilStd GPS, crystal ball etc., is able to
> achieve an accuracy of, say, a few centimeters and uses it to add new
> nodes (POIs) to OSM.
> 
> some time later, mapper B with his/her ancestors mechanical GPS device
> (*), achieving an accuracy of max., say, 15 meters, surveys the same
> area, figures out that (by his/her point of view) POIs added by mapper
> A are 15 meters off and corrects their location. 
> 
> what is needed here is some tag, saying "don't touch these
> coordinates, they've been surveyed with high(est) accuracy".
> 
> I heard this argument from an pipeline expert, noting that marker
> surveyed with consumer GPS are (for their standards) way off their
> real location.
> 
> maybe this is a non-issue after all, if consensus is that consumer
> GPS accuracy is sufficient enough.
> 
> cu

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[Tagging] correct access tagging for tourist attraction

[Richard Welty]

we were using the old skobbler app to get us to the biltmore estate in
Ashville, NC today, and an issue came up with access tagging. specifically,
there are multiple roads that can access biltmore but only one official 
entrance.
the current tagging in OSM labels all the roads as private, with the 
result that

an OSM based GPS app can't distinguish what the correct roads to use
actually are. we ended up at the wrong entrance.

i'm pondering how to tag to distinguish between the preferred private and
the ones that aren't supposed to be used. any suggestions?

richard

--
rwe...@averillpark.net
 Averill Park Networking - GIS & IT Consulting
 OpenStreetMap - PostgreSQL - Linux
 Java - Web Applications - Search


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Re: [Tagging] Distinction between amenity=restaurant and fast_food

[Никита]

> does it serve food? does it serve alcohol? how fast is food available
after ordering? is it table service with waiters? is it counter service
with tables? is takeout available? is there drive thru takeout? is there a
restroom amenity? is there a playground amenity?

This schema is quite meaningfull, but can we actually use these keys? Most
of them are verifable, so lets map them?

Actually takeout is not limited to ff/rest, but also pubs etc.

2014-12-24 14:08 GMT+04:00 Bryce Nesbitt :

> While all restaurants pre-cook some food,
> fast food restaurants often cook the majority of food prior to
> a customer order.
>
> But there's just simply no firm line between restaurant and fast food.
> But there are lots of attributes:
>
> does it serve food?
> does it serve alcohol?
> how fast is food available after ordering?
> is it table service with waiters?
> is it counter service with tables?
> is takeout available?
> is there drive thru takeout?
> is there a restroom amenity?
> is there a playground amenity?
>
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>
>
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Re: [Tagging] correct access tagging for tourist attraction

[johnw]

perhaps use the =destination tag instead of =private on the road you are 
supposed to use. 
http://wiki.openstreetmap.org/wiki/Key:access 


I think that unless you are an invited guest and have a drawn map and 
permission from the owner, a private place that provides access on a certian 
way to visitors would use a different tag than access=private - they expect 
visitors to use that particular way to visit the facility - so 
access=destination seems correct. 

If the other access roads have gates/bollards/rope, tag them as access=no or 
private as well. it will further discourage visitors from using that road. 
http://wiki.openstreetmap.org/wiki/Key:barrier 
 

javbw


> On Dec 25, 2014, at 10:34 AM, Richard Welty  wrote:
> 
> we were using the old skobbler app to get us to the biltmore estate in
> Ashville, NC today, and an issue came up with access tagging. specifically,
> there are multiple roads that can access biltmore but only one official 
> entrance.
> the current tagging in OSM labels all the roads as private, with the result 
> that
> an OSM based GPS app can't distinguish what the correct roads to use
> actually are. we ended up at the wrong entrance.
> 
> i'm pondering how to tag to distinguish between the preferred private and
> the ones that aren't supposed to be used. any suggestions?
> 
> richard
> 
> -- 
> rwe...@averillpark.net
> Averill Park Networking - GIS & IT Consulting
> OpenStreetMap - PostgreSQL - Linux
> Java - Web Applications - Search
> 
> 
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