Questions tagged [dem]
For questions about Digital Elevation Models (DEM), Digital Terrain Models (DTM) and Digital Surface Models (DSM)
509
questions with no upvoted or accepted answers
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Finding geodesically flat regions in DEM data
I'm interested to find regions in some DEM data for Earth that are what I call geodesically flat, i.e. flat in the way that the path light travels is flat in the absence of strong gravitational fields....
- 189
5
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102
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How do I find the correct projection of a DEM to be used for viewshed analysis?
My data download from Earthdata.nasa.gov for a DEM is in WGS84 CRS. I am aiming to create Viewshed using QGIS 3.14 but I am getting the below error message:
Raster pixels are irregular in shape (...
- 126
5
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190
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Calibrating DTMs in QGIS
I downloaded some raw elevation DTMs from QGIS and need to calibrate them to a known height, they are about 10m off. I have a point that I know the elevation to be 174.34m ASL.
I had done the ...
4
votes
0
answers
627
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Making Ridge Line and Valley Line from Contours or DEM using SAGA GIS
How do I make ridge lines and valley lines using open source GIS Software?
I am totally stuck. I found solution in SAGA GIS - also available in QGIS but it freezes when I run it.
http://www.saga-gis....
4
votes
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answers
749
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Where can download a DEM for whole world in a single low resolution image?
I work in Blender to make Earth globe and I need elevation data for whole earth with low spatial resolution to make relief as a terrain.
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4
votes
1
answer
218
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NODATA on MapServer
I am trying to generate a DEM mosaic to publish via a WCS using MapServer. Unfortunately I can not remove the NODATA. In MapServer's own tutorials and discussion groups suggest PROCESSING "NODATA = 0",...
4
votes
0
answers
91
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Refining DEM with topographic survey?
I have a DEM that is based on LiDAR and I would like to refine a small area of the DEM with topographic survey points.
Is there a good way to do this in QGIS?
- 41
4
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answers
284
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"Select a tool" error Saga: Accumulated cost (isotropic)
I'm trying to run Saga's accumulated cost operation in QGIS on a DEM and set of raster destination points, but keep receiving an "Error: select a tool" in the log after a failed run. There are no ...
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4
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946
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QGIS: How to create a crosstab using SAGA toolbox cross calssification and tabulation?
I am trying to use Cross classification and tabulation SAGA toolbox. I have a raster DEM file (14 classes) and raster file precipitation (13 classes). I want to do cross-tab - but I don't know how ...
- 41
4
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251
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Watershed delineation with meandering river?
I'm using ArcGIS (Hydrology toolbox) for watershed delineation for a number of pour points, and I'm running into problems with very meandering rivers on extremely flat alluvial land (Amazon basin).
...
- 213
4
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answers
123
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Blend overlapping DEMs using Open Source / Python
I'd like to blend edges of overlapping DEMs such that the join is a smooth transition (for use with InSAR). Apparently the best interpolation kernel for this, according to the literature, is thin ...
- 131
3
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186
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How to remove noise from a DSM (city center) to create a 3D printable model
For the company I work for, I need to create a 3D printable model of a part of a city's downtown area.
At my disposal (upon request to local government authorities) I have point clouds from LiDAR ...
- 31
3
votes
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answers
39
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LiDAR derived streams - map scale
Historically, streams were defined by the map scale. For example, for a map with a scale of 1:24,000 would mean that the streams identified on that map would be 1:24,000 streams.
With streams that are ...
- 31
3
votes
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answers
90
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How to pick and export the deepest points of a DEM
I am trying to work out how I can pick and export (to XYZ) the deepest path of a DEM.
I have a DEM surface (created from an 20cm XYZ file) where a straight line trench has been cut and I wish to pick ...
- 101
3
votes
1
answer
758
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QGIS Using a directory of 6500 raster DSM geotiff files - How to load/manage?
I have a few windows directories that each have many 1000's of Geotiff DSM/DEM files downloaded from LINZ (Land information NZ) These are derived from 1m LiDAR and each file covers a couple km2
I can ...
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