Could someone provide me with a guide/suggestion/paper on how to generate/calculate the relief map of a region from DEM at a given distance (km) (i.e., radius in km)? The radius could be any value of choice. I desire to understand the spatial variation of relief in the region.
PS: Not the traditional hillshade map from ArcGIS/QGIS.
Greetings Blessing Adeoti
- Generally, a DEM already shows the relief or topography because of its per-pixel representation of the terrain elevation (e.g. see Figures 2 and 3 in my recent paper on AW3D DEM accuracy -
Article Accuracy assessment of ALOS World 3D-30m DEMs using field da...
. - I guess what you require is an enhanced visualization of the DEM to enable a better appreciation of the relief, and to clip the DEM to a specific radius which can be done in ArcGIS or QGIS. Please let me know if I got your question correctly. Thanks.
Thank you Chukwuma John Okolie for your suggestions. Yes, DEM shows the topography and allows qualitative perception of the relief. In my case, I wish to quantitatively estimate the relief (local relief =maximum elevation- minimum elevation, over a given distance for a specific region). Indeed, this statement is will achieve the outcome but I do know how to manipulate either ArcGIS/QGIS or others to achieve this. Please see Thiede et al. 2009, Fig. 5a for a similar figure of local relief generation (Article Erosional variability along the northwest Himalaya
). It is freely available for download. The authors obtained the local relief by measuring the difference between minimum and maximum elevation within 10 km diameter windows around each pixel in the DEM (SRTM90). Take note that along the river, relief is highest whereas in the normal DEM, elevation value will be lowest along the river. I am thinking probably using Zonal Statistics tool might help. Please let me know what you think. Thanks.
Dear Blessing Adeoti.
I think this paper will help you lot.
Title- Effects of analytical window and resolution on topographic relief derived using digital elevation models
Author- Yingkui Li
Okay now I understand what you mean Blessing Adeoti
This video tutorial on the calculation of relative relief using QGIS software should be helpful - https://www.youtube.com/watch?v=OIokx7UkEic
Dear Readers, I figured it out.
The local relief can be calculated in ArcGIS by using the function FOCAL STATISTICS (RANGE option). It is part of Spatial Analyst tool ---->>> Neighborhood --->> Focal statistic. It tool allows you to set the neighborhood distance. Everything (DEM) should be done in UTM-coordinate system. Afterwards you need to apply some smoothing for obtain the final result because of some artifacts in the DEM. For the smoothing, I used Filter function (still under the Neighborhood tool).
Best wishes and thanks for previous suggestions Chukwuma John Okolie Shashi Sekhar
For high precision, you might need to re digitise your original topographic data at a smaller distance (this can be done using Surfer or Grapher packages as well as ArchGis or Geosoft), and thereafter the moving-average filter or any other filters that can reduce stiffness in your enveloped surfaces can be applied to reduce errors (minimising residuals).
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