[GRASS-user] Introducing myself and my first questions

Paul Meems bontepaarden at gmail.com
Thu Dec 27 05:40:13 PST 2012

Hi list,

I've just subscribed to this list as suggested by Daniel Lee (see mail send
approx. 30 min. ago).

I'm a new user to GRASS GIS. I have some experience with ArcMap v9.3 and am
a long-term user and developer of MapWindow GIS (www.mapwindow.org).
I'm mainly working on Windows, but I'm learning Ubuntu server.
On this Ubuntu server I have GeoServer with OpenLayers.

I'm working together with someone who's made a nice model in ArcGIS.
I'm trying to convert this model to GRASS.

I've downloaded the Windows version of GRASS GIS 6.4.3RC2. When I have
successfully converted the model to GRASS I plan to use the Ubuntu version.
My Ubuntu server runs in the cloud so it is very easy to increase RAM and
HD when I want to start calculating.
The current ArcMap version of the model is very labor-intensive, very slow,
not very stable and very costly (license costs).

This model starts with a high-resolution DEM file. The first step is to
calculate the solar radiation for the whole year. I have already converted
the 39 w001001.adf files to a single GeoTiff using GDAL.
For testing purposes I've clipped a part. This part I'll be using.

I've already understood I need r.sun and I need to calculate the radiation
for each day.

On the 'Required' tab I select for 'input raster map' my clipped tiff file.
For 'no. day' I set 1.

The 'Input options' tab already raises questions for me. For aspect and
slope map in ArcMap FROM_DEM is used so I select my clipped tiff again. My
area is located in The Netherlands so I use 90 for aspect. I don't see
something in ArcMap that looks like linkein so I leave this blank. The same
for albedo. I'm not sure what to use for longin and latin. My tiff is
projected (Amersfoort/RD_New). I'm not sure either what to use for coefbh,
coefdh, horizon or horizonstep.

On the 'Output options' tab I'm completely puzzled. I would have expected
to set file names but all I can do is select my clipped tif.

The 'Optional' tab. I want the calculation to use nearby houses, trees and
chimneys so I check 's'. 'step' I keep as 0.5, assuming this is the same as
ArcMap's 'hour interval'. I don't know what declin or dist should be. For
time Mode 1 is mentioned. What are the different modes?

For ArcMap I need to pass the Latitude. I can't find that for r.sun.
I've attached a screenshot of the settings used for ArcMap.
[image: Inline afbeelding 1]

I've read the manual tab but a lot of knowledge is assumed which I don't
yet have ;)
And I see some settings in ArcMap which I cannot map in GRASS.

So if anybody can help that would really be helpful.


Paul Meems
The Netherlands
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