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Try working with specific value for the latitude you are working. Check this<br><br>http://www.csgnetwork.com/degreelenllavcalc.html<br><br>As I understand Gdal uses the lenght of a degree of latitude in meters of feet, so this can help to solve the problem.<br><br>Gerardo Jiménez Delgado<br>Instituto de Investigaciones Antropológicas<br>Universidad Nacional Autónoma de México<br>Ciudad Universitaria s/n<br>Coyoacan 04510
Mexico City<br>Mexico
56 22 95 16<br><br><div><div id="SkyDrivePlaceholder"></div><hr id="stopSpelling">Date: Wed, 11 Jan 2012 20:30:30 +0530<br>Subject: Re: [Qgis-user] Slope and area/length calculations with Geographic CRS<br>From: harry.om2000@gmail.com<br>To: gejst5@hotmail.com<br><br>Thanks! it is working well.<br><br>For feet it seems that slope is less on each pixel with the scale value 370400 so we can increase the value and check again,<br>but for meters with scale value of 111120, it is working well and equal to the slope found with Projected CRS on each pixel.<br>
<br>Thanks Again!<br><br>Regards<br><br><div class="ecxgmail_quote">On Wed, Jan 11, 2012 at 7:41 PM, Gerardo Jimenez <span dir="ltr"><<a href="mailto:gejst5@hotmail.com">gejst5@hotmail.com</a>></span> wrote:<br><blockquote class="ecxgmail_quote" style="border-left:1px #ccc solid;padding-left:1ex">
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For slope calculations with lat lon coordinates and elevation units in meters or feet you have to be aware to set the proper "scale (ratio of vertical unit to horizal units)" value. Gdal help recomends using 111120 if vertical units are in meters and 370400 if they are in feet. <div>
<br></div><div>See</div><div><a href="http://www.gdal.org/gdaldem.html" target="_blank">http://www.gdal.org/gdaldem.html</a></div><div><br>Hope it helps<br><br>Gerardo Jiménez Delgado<br>Instituto de Investigaciones Antropológicas<br>
Universidad Nacional Autónoma de México<br>Ciudad Universitaria s/n<br>Coyoacan 04510
Mexico City<br>Mexico
56 22 95 16<br><br><div><div></div><hr>Date: Wed, 11 Jan 2012 19:18:51 +0530<br>From: <a href="mailto:harry.om2000@gmail.com">harry.om2000@gmail.com</a><br>To: <a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br>
CC: <br>Subject: [Qgis-user] Slope and area/length calculations with Geographic CRS<div><div class="h5"><br><br>Respected All,<br><br>When we have to calculate area/length in polygon/line vector layers we have to convert Geographic CRS of the layer in Projected CRS, and in raster DEM for slope calculations the same is to be done.<br>
<br>I am providing continuous free practical trainings to the Government officials in India of 5-6 days on Application of Desktop QGIS in Watershed/Rural Development schemes and in this duration I don't want to put the trainees deep in the matter of Coordinate Reference System and want to do everything in GCS-WGS1984. Can there be any solution presently or in future for calculating area/length in vector and slope etc. in DEM with geographic coordinate system. <br>
<br>Regards<br><br>Harish<br><br>-- <br>Harish Kumar Solanki, Assistant Professor<br>National Institute of Rural Development (NIRD), MoRD, GoI <br>Jaipur, INDIA- 302006<br><br><br>Email- <a href="mailto:hksolanki@nird.gov.in">hksolanki@nird.gov.in</a>, <a href="mailto:harry.om2000@gmail.com">harry.om2000@gmail.com</a>, <br>
Tele-Fax-0141-2209904, Mo.- 09414291732, 09214446732<br>Website- <a href="http://www.nird.org.in" target="_blank">http://www.nird.org.in, http://watershed.rajasthan.gov.in/</a><br>LinkedIn: <a href="http://www.linkedIn.com/in/hksolanki" target="_blank">www.linkedIn.com/in/hksolanki</a><br>
<a href="http://www.nird.org.in" target="_blank"></a><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Harish Kumar Solanki, Assistant Professor<br>National Institute of Rural Development (NIRD), MoRD, GoI <br>Jaipur, INDIA- 302006<br><br><br>Email- <a href="mailto:hksolanki@nird.gov.in">hksolanki@nird.gov.in</a>, <a href="mailto:harry.om2000@gmail.com">harry.om2000@gmail.com</a>, <br>
Tele-Fax-0141-2209904, Mo.- 09414291732, 09214446732<br>Website- <a href="http://www.nird.org.in" target="_blank">http://www.nird.org.in, http://watershed.rajasthan.gov.in/</a><br>LinkedIn: <a href="http://www.linkedIn.com/in/hksolanki" target="_blank">www.linkedIn.com/in/hksolanki</a><br>
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