[HOT] Advice tracing footprints with poor imagery in Kathmandu, Nepal

Mikel Maron mikel_maron at yahoo.com
Fri Feb 8 16:42:59 GMT 2013


>  I imagine any proposed import would run into similar issues, particularly since the> imagery in Nepal is likely not as good as the multispectral+lidar that
> vtcraghead had.
 
Yes, but also consider other ways of using this LIDAR data.
LIDAR, with aerial imagery, could be another useful source for manual editing. Imagine a tasking manager job, that included lidar derived tiles, in order to map rough building height.

-Mikel

* Mikel Maron * +14152835207 @mikel s:mikelmaron


>________________________________
> From: Paul Norman <penorman at mac.com>
>To: 'maning sambale' <emmanuel.sambale at gmail.com>; 'Ryan Sommerville' <ryan.sommerville at gmail.com> 
>Cc: hot at openstreetmap.org 
>Sent: Friday, February 8, 2013 2:38 AM
>Subject: Re: [HOT] Advice tracing footprints with poor imagery in Kathmandu, Nepal
> 
>> From: maning sambale [mailto:emmanuel.sambale at gmail.com]
>> Subject: Re: [HOT] Advice tracing footprints with poor imagery in
>> Kathmandu, Nepal
>> 
>> There are opensource tools that can extract features from hires imagery,
>> an example is GRASS, see this sample process (ignore the subjectline :))
>> 
>> http://lists.osgeo.org/pipermail/grass-user/2007-August/040808.html
>> 
>> But this requires, that you have direct access to the imagery (which
>> isn't legally allowed with Bing)
>> 
>> Another option for small areas is to try balloon/kite mapping:
>> 
>> http://grassrootsmapping.org/
>> 
>> In my experience, the most effective way is by manually tracing in JOSM
>> (no computer algorithm can do what a human can see, at least not
>> yet) and of course ground validation.
>
>The last time someone proposed importing automatically generated building
>outlines[1] the consensus was against it. They used multispectral imagery
>and LIDAR coverage and there were still significant concerns about the
>quality. One of the basic problems with automatic building detection is that
>buildings tend to consist of right angles but automatic detection methods
>tend be better with irregularly shaped areas like tree coverage. I imagine
>any proposed import would run into similar issues, particularly since the
>imagery in Nepal is likely not as good as the multispectral+lidar that
>vtcraghead had.
>
>[1]: http://lists.openstreetmap.org/pipermail/imports/2012-March/001267.html
>
>
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