<div dir="ltr"><div><div>Hi Markus,<br><br></div>I was using r.terraflow because I had converted my voids to negative values while the areas outside the country where set to null.<br>But the data is proving to be too big and I'll just skip the gap-filling for now. Might do it later on, filling the gaps in the import process.<br><br>The SRTM v3 you pointed out is very good but it's the 3-arcsec resolution. I'm working with the 1-arcsec res.<br><br></div>Cheers and thanks<br>Daniel<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jan 13, 2015 at 5:40 PM, Markus Metz <span dir="ltr"><<a href="mailto:markus.metz.giswork@gmail.com" target="_blank">markus.metz.giswork@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Tue, Jan 13, 2015 at 7:52 PM, Daniel Victoria<br>
<<a href="mailto:daniel.victoria@gmail.com">daniel.victoria@gmail.com</a>> wrote:<br>
><br>
> Now, the thing is, my main interest is to fill the voids in the SRTM data.<br>
> So I though about using r.terraflow to get the filled elevation. Should I<br>
> continue on that path or would it be better to use r.fill.null on a large<br>
> dataset?<br>
<br>
</span>r.terraflow does not fill voids, it fills sinks. Use SRTM v3 [0], this<br>
is gap-filled. Using r.fill.null on SRTM v2 will not give you the same<br>
quality. r.terraflow has a limit on the number of rows and columns<br>
(max 32,767 each). r.watershed also has a limit on the number of rows<br>
and columns, but that is max 2,147,483,647 each. In any case, you<br>
should use GRASS 7 for such large datasets.<br>
<br>
Markus M<br>
<br>
[0] <a href="https://lpdaac.usgs.gov/products/measures_products_table/srtmgl3" target="_blank">https://lpdaac.usgs.gov/products/measures_products_table/srtmgl3</a><br>
<div class="HOEnZb"><div class="h5"><br>
><br>
> Thanks<br>
> Daniel<br>
><br>
> On Tue, Jan 13, 2015 at 1:46 PM, Daniel Victoria <<a href="mailto:daniel.victoria@gmail.com">daniel.victoria@gmail.com</a>><br>
> wrote:<br>
>><br>
>> Charlie,<br>
>><br>
>> I just downloaded some SRTM 1arc sec. from EarthExplorer. The data is<br>
>> supplied in 3 different file types, GeoTIFF, DTED or BIL and they are all in<br>
>> Integer values (Int16). No floating point elevation values.<br>
>><br>
>> Cheers<br>
>> Daniel<br>
>><br>
>> On Tue, Jan 13, 2015 at 12:12 PM, Charlie Shobe <<a href="mailto:chsh5846@colorado.edu">chsh5846@colorado.edu</a>><br>
>> wrote:<br>
>>><br>
>>> Hi Daniel,<br>
>>><br>
>>> I believe that SRTM data does in fact provide floating point elevation<br>
>>> values, so you may want to try working with the DEM as type FCELL from the<br>
>>> very beginning. I don't know if this will help solve your problem, but the<br>
>>> last time I brought in SRTM (1 arc second) data it was type FCELL and<br>
>>> contained several decimal places of precision.<br>
>>><br>
>>> Good luck,<br>
>>><br>
>>> Charlie<br>
>>><br>
>>><br>
>>> On Jan 13, 2015, at 4:00 AM, Daniel Victoria <<a href="mailto:daniel.victoria@gmail.com">daniel.victoria@gmail.com</a>><br>
>>> wrote:<br>
>>><br>
>>> Stephan, I'll give r.watershed a try and let it run for a couple of days.<br>
>>> Thanks<br>
>>><br>
>>> Thayer, I used r.recode because the person that sent me the data messed<br>
>>> up the null values. So in order to fix that I did:<br>
>>> 1) use r.external to bring the data to Grass<br>
>>> 2) fix null values with r.recode, which was faster than r.null<br>
>>><br>
>>> But I gave up on that path and since imported the data (r.in.gdal) and<br>
>>> fixed the null values with r.null.<br>
>>> I'm also using integer values (CELL type) because from what I heard, SRTM<br>
>>> does not provide floating point data.<br>
>>><br>
>>> Now I tried to run r.terraflow but I got a type error which asked me to<br>
>>> use r.terraflow.short. Since I don't have that command in my grass<br>
>>> instalatin, I converted the SRTM data to float. But that was to no avail<br>
>>> since it's now giving me a dimensions type overflow error and asking me to<br>
>>> change the dimension_type and recompile.<br>
>>><br>
>>> I'll give r.watershed a try. If that does not work, I'll see if I can<br>
>>> recompile.<br>
>>><br>
>>> Thanks<br>
>>> Daniel<br>
>>><br>
>>> On Mon, Jan 12, 2015 at 9:22 PM, Thayer Young <<a href="mailto:thayeray@yahoo.com">thayeray@yahoo.com</a>> wrote:<br>
>>>><br>
>>>> With regards to the size of DEM, if you can get the command to run it<br>
>>>> may take several days to finish, this is more than twice the size of the<br>
>>>> Washington State DEM that took the authors 33 hours in 2003 (Arge, Chase,<br>
>>>> Halpin, Toma, Urban, Vitter, Wickremesinghe Efficient Flow Computation on<br>
>>>> Massive Grid Terrain Datasets Geoinformatica Volume 7 Issue 4, December 2003<br>
>>>> Pages 283 - 313 ). My mid-2014 computer runs at about twice the speed<br>
>>>> quoted in the paper.<br>
>>>><br>
>>>> Did you r.recode it to make it smaller? In flat areas you need the data<br>
>>>> contained after the decimal point to allow the flow a chance to make it down<br>
>>>> hill, otherwise you can get streams going no where near where they do in<br>
>>>> real life. I have never tried running r.terraflow on an integer raster, I<br>
>>>> know that it works on decimal rasters.<br>
>>>><br>
>>>> -Thayer<br>
>>>><br>
>>>><br>
>>>><br>
>>>> ________________________________<br>
>>>><br>
>>>> Date: Mon, 12 Jan 2015 09:59:40 -0200<br>
>>>> From: Daniel Victoria <<a href="mailto:daniel.victoria@gmail.com">daniel.victoria@gmail.com</a>><br>
>>>> To: grass <<a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a>><br>
>>>> Subject: [GRASS-user] r.terraflow on massive DEM<br>
>>>> Message-ID:<br>
>>>> <CA+irsJjf7xhWgU968D+4+xc2YGJ=_<a href="mailto:n4xJtP0_WeU1ZpoRTt9ng@mail.gmail.com">n4xJtP0_WeU1ZpoRTt9ng@mail.gmail.com</a>><br>
>>>> Content-Type: text/plain; charset="utf-8"<br>
>>>><br>
>>>><br>
>>>> Hi list,<br>
>>>><br>
>>>> I'm trying to run r.terraflow on a very large DEM but I wander if it's<br>
>>>> __too large__.<br>
>>>><br>
>>>> The region dimensions are:<br>
>>>> ncol=141114<br>
>>>> nrow=140487<br>
>>>> Data type = CELL<br>
>>>><br>
>>>> The map is actually a reclass map of a raster that I imported using<br>
>>>> r.external.<br>
>>>><br>
>>>> When I run r.terraflow I get:<br>
>>>><br>
>>>> r.terraflow elevation=srtm_brasil@PERMANENT filled=srtm_fill<br>
>>>> direction=flowdir swatershed=sink accumulation=flowacc tci=srtm_tci<br>
>>>> directory=E:\terraflow_temp<br>
>>>><br>
>>>> WARNING: raster srtm_brasil is of type CELL_TYPE --you should use<br>
>>>> r.terraflow.short<br>
>>>> ERROR: [nrows=140487, ncols=141114] dimension_type overflow -- change<br>
>>>> dimension_type and recompile<br>
>>>> (Mon Jan 12 09:57:18 2015) Command finished (0<br>
>>>> sec)<br>
>>>><br>
>>>> However, I don't have an r.terraflow.short command<br>
>>>> I'm running Grass 7.0.0beta4 from OsGeo4W<br>
>>>><br>
>>>> Cheers<br>
>>>> Daniel<br>
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