[Qgis-user] Slope and area/length calculations with Geographic CRS

[Marco Hugentobler]

Hi

In the newest developer version, the raster terrain plugin in QGIS has 
been significantly improved (hillshade function, relief). As part of 
these improvements, it is now also possible to set this scale factor 
(111120 or 370400 for feet) in the QGIS plugin. More details about the 
plugin improvement, especial the relief functionality, will be described 
in a blog article soon.
The work was kindly funded by the Swiss Humanitarian Aid unit 
(http://www.deza.admin.ch/en/Home/Activities/Humanitarian_Aid/Swiss_Humanitarian_Aid_Unit).

Regards,
Marco

On 11.01.2012 15:11, Gerardo Jimenez wrote:
> 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.
>
> See
> http://www.gdal.org/gdaldem.html
>
> Hope it helps
>
> Gerardo Jiménez Delgado
> Instituto de Investigaciones Antropológicas
> Universidad Nacional Autónoma de México
> Ciudad Universitaria s/n
> Coyoacan 04510 Mexico City
> Mexico 56 22 95 16
>
> ------------------------------------------------------------------------
> Date: Wed, 11 Jan 2012 19:18:51 +0530
> From: harry.om2000 at gmail.com
> To: Qgis-user at lists.osgeo.org
> CC:
> Subject: [Qgis-user] Slope and area/length calculations with 
> Geographic CRS
>
> Respected All,
>
> 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.
>
> 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.
>
> Regards
>
> Harish
>
> -- 
> Harish Kumar Solanki, Assistant Professor
> National Institute of Rural Development (NIRD), MoRD, GoI
> Jaipur, INDIA- 302006
>
>
> Email- hksolanki at nird.gov.in <mailto:hksolanki at nird.gov.in>, 
> harry.om2000 at gmail.com <mailto:harry.om2000 at gmail.com>,
> Tele-Fax-0141-2209904, Mo.- 09414291732, 09214446732
> Website- http://www.nird.org.in, http://watershed.rajasthan.gov.in/ 
> <http://www.nird.org.in>
> LinkedIn: www.linkedIn.com/in/hksolanki 
> <http://www.linkedIn.com/in/hksolanki>
>
>
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux&  Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee

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