[GRASS-user] Horizon Model (was Airborne LiDAR data strip adjustment)

[Rebecca Bennett]

Hi Adrian,

This is the approach I used to calculate SVF in GRASS (as you probably know). You can test the similarity to Kokalj et al's original algorithm by processing another copy from your DTM using their ENVI plugin or standalone tool from here http://iaps.zrc-sazu.si/en/svf#v and running some visual or quantitative assessments 


FWIW I can't remember if I did a quantitative comparison of the horizon images I created against the SFV I made from teh standalone (for me it was sufficient that the process and variables of horizon view creation in GRASS were methodologically the same as the published SVF, and visually they were identical)

Good luck!
Rebecca




>________________________________
> From: Adrian Kirilov <kirilov.adrian at gmail.com>
>To: Hamish <hamish_b at yahoo.com> 
>Cc: GRASS user list <grass-user at lists.osgeo.org> 
>Sent: Sunday, 19 May 2013, 13:57
>Subject: Re: [GRASS-user] Fwd: Airborne LiDAR data strip adjustment
> 
>
>
>I applied the same method actually (after a bit thinking and reevaluation of my first idea). I prefer to use v.in.ascii -t -r -z input= fs= z= out= , because I'm interpolating the points with v.surf.bspline (bilinear, to be more precise) afterwards.
>
>
>I have some more questions now. Sorry, but I don't know if I should put them in a different e-mail and subject...
>
>
>I used r.horizon module to build horizon view for 16 directions, consequently I received as a result 8 output raster maps:
>r.horizon elevin=demb30_5_combined at FlemishArdennes direction=0 horizonstep=45 maxdistance=10 horizon=SVF_demb30_5 
>
>
>
>After that I combined them witn r.mapcalc but with simple addition only:
>
>
>
>r.mapcalc:
>'SVF_demb30_5_0 at FlemishArdennes + SVF_demb30_5_1 at FlemishArdennes + SVF_demb30_5_2 at FlemishArdennes + SVF_demb30_5_4 at FlemishArdennes + SVF_demb30_5_5 at FlemishArdennes + SVF_demb30_5_6 at FlemishArdennes + SVF_demb30_5_7 at FlemishArdennes'
>
>
>Is this approach correct?
>
>
>And how can I change the range value of the output raster after I have set up first color table with r.colors color=grey. I want to change the range from 0.0-1.0 to something else, like 0.7-1.0 for example to get more contrast or brightness. The last is in fact the question from my first e-mail (see up) with this subject.
>
>
>Thanks a lot for the help!
>
>
>
>
>Greetings,
>
>
>Adrian Kirilov 
>
>
>
>On Sat, May 18, 2013 at 5:37 AM, Hamish <hamish_b at yahoo.com> wrote:
>
>Adrian wrote:
>>> It's a series of points. But how can I export them from all
>>> imported files (strips) later into a single one ASCII file into
>>> specific region? I think that v.out.ascii for example is only
>>> for exporting single file. And I need to export multiple,
>>> falling into the region. Is this possible in GRASS?
>>
>>first set the region and grid size with g.region, check it is
>>ok with the -p flag.
>>
>>then depending on what you want to do:
>>
>>cat *.asc | r.in.xyz x= y= z= fs= input=- output=mapname method=
>>
>>  or
>>
>>cat *.asc | v.in.ascii -r -bt x= y= z= fs= output=mapname
>>
>>
>>r.in.xyz discards points outside of the current region, as does
>>v.in.ascii if you use the -r flag.
>>
>>
>>
>>if your data is already processed, sorted, and cleaned I'd
>>go straight for r.in.xyz myself, but that's just me.
>>
>>
>>Hamish
>>
>
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