https://redmine.auroville.org.in/https://redmine.auroville.org.in/favicon.ico2019-06-14T11:45:26ZRedmineGIS - Task #8486: Understanding how to generate a DSM (Digital Surface Model) or DEM (Digital Elevation Model) using Survey Points.https://redmine.auroville.org.in/issues/8486?journal_id=513302019-06-14T11:45:26ZDebojyoti Mallickdebojyoti.mallick@outlook.com
<ul><li><strong>Assignee</strong> set to <i>Debojyoti Mallick</i></li></ul> GIS - Task #8486: Understanding how to generate a DSM (Digital Surface Model) or DEM (Digital Elevation Model) using Survey Points.https://redmine.auroville.org.in/issues/8486?journal_id=517102019-06-20T11:05:46ZDebojyoti Mallickdebojyoti.mallick@outlook.com
<ul></ul><p>Debojyoti Mallick wrote:</p>
<blockquote>
<p>Looking at the pros and cons for generating a DSM.</p>
<p>Can use this example as a reference model: <a class="external" href="http://distancesampling.org/R/vignettes/hare_point_transect_dsm.html">http://distancesampling.org/R/vignettes/hare_point_transect_dsm.html</a></p>
</blockquote>
<p>A python example of using Delaunay 2D triangles: <a class="external" href="https://github.com/amuriy/GRASS-scripts/blob/master/Python/v.triangle.py">https://github.com/amuriy/GRASS-scripts/blob/master/Python/v.triangle.py</a></p> GIS - Task #8486: Understanding how to generate a DSM (Digital Surface Model) or DEM (Digital Elevation Model) using Survey Points.https://redmine.auroville.org.in/issues/8486?journal_id=522412019-07-03T06:14:15ZDebojyoti Mallickdebojyoti.mallick@outlook.com
<ul></ul><p>Debojyoti Mallick wrote:</p>
<blockquote>
<p>Looking at the pros and cons for generating a DSM.</p>
<p>Can use this example as a reference model: <a class="external" href="http://distancesampling.org/R/vignettes/hare_point_transect_dsm.html">http://distancesampling.org/R/vignettes/hare_point_transect_dsm.html</a></p>
</blockquote>
<p>Our motive here is to use different elevation models to best identify the ridges for the basins.</p>
<p>I did run through Swathi's results where she used different interpolation techniques to generate a raster from the surveyed elevation points.</p>
<p>As per the previous findings the best results were shown using the B-Spline method.</p>
<p>We conducted an additional test using the raster generated from calculation slope using the SAGA's IDW toolset in QGIS.</p>
<p>The logic here was to find the desired slope between two elevation points.<br />Once a slope gradient was established between the elevation points in the raster we converted the raster file to vector points.</p>
<p>This would mean each pixel (depending on the dpi and pixel value ) would be converted to a vector point based on a value defined by the raster cell's slope gradient. <br />Essentially each point would have a particular elevation value.<br />The result was visually pleasing but there are additional factors to be considered.</p>
<p>Firstly we need the X, Y and Z coordinated included for these points. This can be generated from the defined projection system#</p>
<p>Cons of this method:<br />- This creates additional points which moves away from the original data<br />- This generates very large datasets which are not suitable for further workflows<br />- In addition to this , the methodology leads to a pointless loop of Vector to Raster to Vector again.</p>
<p>Conclusion:<br />Working with either the known elevation points or the generated raster to find ridges without further interpolation makes more sense.</p> GIS - Task #8486: Understanding how to generate a DSM (Digital Surface Model) or DEM (Digital Elevation Model) using Survey Points.https://redmine.auroville.org.in/issues/8486?journal_id=522422019-07-03T06:14:37ZDebojyoti Mallickdebojyoti.mallick@outlook.com
<ul><li><strong>Status</strong> changed from <i>New</i> to <i>In Progress</i></li></ul>