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<DIV><FONT face=Arial color=#000000 size=2>Hi all,</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I would like to submit to you the following "work plan" that I figured out to do a particular job:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I need to apply the module r.horizon (add-on from JRC) that computes the angular height of terrain horizon from a given point and a given DEM raster.</FONT></DIV>
<DIV><FONT size=2>That DEM should be as large as possible to let the module create an horizon profile as much realistic as possible.</FONT></DIV>
<DIV><FONT size=2>I have two types of GIS data of the interested area to work on:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>A) the SRTM database, 90m resolution, WGS84</FONT></DIV>
<DIV><FONT size=2>B) a local GIS database, with a resolution of 20m, Gauss-Boaga Rome40 West (preferred, because of the better resoultion)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>all the data are in arc-info ASCII format.</FONT></DIV>
<DIV><FONT size=2>Since I don't want to create confusion within different data and projects, I decided to create two main locations: a Gass-Boaga local for the local database, in which import ASCII data usign r.in.arc module, and an WGS84 location for the SRTM database (using r.in.arc here too).</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>While the SRTM data are organanized in big maps, where a single map covers all the interested area, the Local database is fragmented in multiple small (but contiguos) maps; because of that I need to patch all of them to have a sufficient working area. But that's not still enough, since some points of interest lay</FONT><FONT size=2> on the borders of such local map: that's why I need to patch the local database *big map* (all the maps patched together) with the SRTM map (only one map is needed), with the following goals:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>1. obtain a map with the local map data, where those are present, and with the SRTM data where the local data are not present (null)</FONT></DIV>
<DIV><FONT size=2>2. do not alter the original data of both locations during patching or resampling (for example for SRTM passing from 90m resolution to 20m)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I try to briefly summarize the steps of the procedure I figured out to reach that goals:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>1. Create a Gauss-Boaga location (call it GB location) and import the local database (native resolution 20m) with r.in.arc</FONT></DIV>
<DIV><FONT size=2>2. Set the region in order to contain all the GB maps and patch all the imported maps (contiguous) to create the *big map*</FONT></DIV>
<DIV><FONT size=2>3. Create a WGS84 location (call it SRTM location) and import the needed DRTM map (native resolution 90m) with r.in.arc</FONT></DIV>
<DIV><FONT size=2>4. Create another WGS84 location (all it JOB location; I create it new because I prefer to preserve the *original* locations) and set the region to fit the interested area</FONT></DIV>
<DIV><FONT size=2>5. In the JOB Location: r.proj the GB big map, maintaining the orginal resolution (20m)</FONT></DIV>
<DIV><FONT size=2>6. r.proj the SRTM map, setting the resolution to 20m (against the original of 90m) during the reprojection (to let me patch it with the GB map that has a 20m res)</FONT></DIV>
<DIV><FONT size=2>7. r.patch the GB big map and the SRTM map, putting the GB raster as first in the input parameter to achieve the goal n°1</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>My doubt is: moving from the 90m resolution to 20m in the SRTM map I will oversample, right? but I will actually maintain the original data (that it is what I want).</FONT></DIV>
<DIV><FONT size=2>Instead, if I resample the SRTM data (using one of r.resamp.* modules) I would obtain a smooth DEM, but I would also alterate the original data, introducing *dangerous* fake data, and so possible critical errors.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Do you agree?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Thanks for all,</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Marco</FONT></DIV></BODY></HTML>