Questions tagged [dem]
For questions about Digital Elevation Models (DEM), Digital Terrain Models (DTM) and Digital Surface Models (DSM)
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Reading elevation data from DEM files using memory mapped files?
I'm aware of GDAL libraries but am supposed to not use them.
Is there a way to use mmap or memory mapped files to access the specific longitude, latitude and elevation values from a .DEM file?
The ...
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0answers
7 views
Performing DTM compression using ArcPy?
I have a set of 32-bit TIFF files of DTM data (50 sm) and I need to save them as 16-bit.
In order to save some space, I compressed them using LZW algorith and saved as 16 bit tiffs using Arcpy.
But ...
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0answers
12 views
Finding the local extrema contour line on a DEM
I need to trace the top of a small levee on the side of a riverbank, based on a DEM.
This line is similar to a contour line, except that it goes through the local maximum instead of a constant level....
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0answers
29 views
Creating DEM from contour pyQGIS? [duplicate]
How can I create Digital Elevation Model using python codes in QGIS software?
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2answers
33 views
Cannot read pixel value from DTM raster with QGIS
I am using this DTM:
http://ags.cuzk.cz/arcgis2/services/dmr4g/ImageServer/WMSServer?request=GetCapabilities&service=WMS
At ArcGIS I am able to ready pixel value of the raster but at QGIS it ...
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0answers
21 views
Creating 3D image from HGT DEM file? [duplicate]
I tried Displaying 3D raster/vector in GRASS from command line?: Error there is no nviz in my GRASS 7.6.x
Already tried this too: Error m.nviz.image bad server connection
Already see this and the ...
3
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1answer
51 views
Generate a viewshed and merge it with another image using GRASS/GDAL command line? [closed]
I've found a tutorial showing exactly what I want to do (merge viewshed and hill shade or map) but unfortunately it is for QGIS users and I need it in pure command line instructions because I'm in a ...
2
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0answers
41 views
Generate an accurate DTM with photogrammetry?
I generated imagery from a low flying drone (40 M AGL) equipped with a mica sense RedEdge multi-spectral camera and have processed the imagery in PIX4D and now am attempting to do some analysis in ...
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21 views
How to remove bridges and dams from DEM
Is there anyway to alter elevation of DEM where there are bridges and dams for the flood routing of the River?
I have to calculate discharge of the River from ancient times so at that time there ...
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0answers
18 views
Flow Distance Not Calculating for Entire Raster
I am trying to calculate the height above the nearest stream for an area. The problem is, it only does so for a portion ( the colored area below) of my area of interest. In the pic below, the black ...
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0answers
20 views
Elevation Map from Slope and Aspect Rasters
I am trying to create an elevation map (e.g., recreate a DEM) from the following input data:
Slope Raster
Aspect Raster
ASCII file containing XYZ data points (Easting, Northing, and Elevation for ...
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1answer
35 views
Why is my DEM so bright for some tiles?
I downloaded an SRTM DEM GeoTIFF file from Earth Explorer. It looks fine when previewing it on Earth Explorer (see picture) but when added in ArcGIS Pro the DEM looks too bright in some of its tiles.
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1answer
20 views
Extrude building footprints using raster (DSM) values in ArcGIS Pro?
Is there a way to extrude a buildings footprint shapefile into 3D buildings using values from the area's DSM in ArcGIS Pro?
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2answers
51 views
Learning DEM resources? [closed]
I'm starting on a problem where I need to find the high point inside a polygon that exists inside the bounds of a DEM tile. I'm teaching myself GDAL and I'll be using Python to access the GDAL library....
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2answers
51 views
Creating contour file from DEM?
Using a 3-meter DEM, can I create an accurate 5 feet interval contour file?
Or is the minimum interval contour I can get is 10 feet (roughly 3 meters)?
3
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1answer
49 views
CHM (Canopy height model) = DSM (Digital surface model) - DTM (Digital terrain model)
I want to create a canopy height model (CHM) which has the height of objects (trees, building, etc.) from DSM and DTM. Below is the step by step procedures which I did so far.
I use open source s2p ...
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1answer
65 views
Creating 3D image from HGT files?
Is there any command line tool to create a 3D terrain from a DEM SRTM HGT file like this?
I mean, given a camera position, a HGT file and a satelite image.
EDIT 1
First try to adapt mdsumner's ...
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0answers
22 views
Editing DEM file
I'm currently working on a small town flood inundation mapping , the DEM file i am using for simulation contains a breakwater built after a recent flood event. My question is if it is possible to edit ...
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2answers
42 views
Lunar DEM elevation data scaled by 2
I am working with a DEM of the lunar south pole in QGIS. I have currently set the projection to "no projection", or Cartesian co-ordinates (origin at the pole). The horizontal locations of features ...
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0answers
18 views
No result with VRM tool ArcGIS
I am using ArcMap version 10.5. I downloaded the VRM tool from here: http://www.arcgis.com/home/item.html?id=9e4210b3ee7b413bbb1f98fb9c5b22d4. I followed the steps in 'read me;
Unzip files (readme....
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2answers
68 views
Classify DEM pixels
I have a differential surface model dataset. That was made: DSM subtracted from DTM, so for example trees have negative height. It is a raster (TIFF) dataset, Type=Float32.
I want to create a ...
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0answers
19 views
Seeking mosaicked global DEM? [migrated]
I would like to know if there is already available mosaicked global dem?
In this site, they provide SRTM (https://cgiarcsi.community/data/srtm-90m-digital-elevation-database-v4-1/) but it does not ...
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0answers
15 views
r.surf.area is underestimating area and giving negligible area
I am using r.surf.area in GRASS GIS to estimate surface area of a DEM. DEM is in EPSG4326 WGS84. It is giving a negligible area. Please give solution to this. Following is the output of r.surf.area.
1
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1answer
44 views
Error creating DEM with Nearest Neighbour tool in QGIS?
I have an issue when I am creating a DEM with the tool natural neighbour on QGIS.
When I extract my data directly on Qgis I have no issue creating a DEM. My points are coming from different sources ...
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0answers
20 views
GRASS r.sun returns “ERROR: insol_time and incidout are incompatible options”
I'm trying to measure irradiance on a DEM using the r.sun tool in QGIS 3.6. I have grids for the elevation (EPSG:32735 - WGS 84 / UTM zone 35S), the slope and aspect (EPSG:4326 - WGS 84). I've tried ...
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1answer
66 views
r.surf.area command of GRASS GIS is giving a very small area
I am a beginner to GIS systems and am trying to calculate the surface area of a dem using r.surf.area command of GRASS GIS. The surface area it is giving me is unacceptable as it is very small. It is ...
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0answers
31 views
Assessing quality (accuracy and precision) of digital surface model (DSM)?
I have been trying to build digital surface model from stereo satellite images.
I do some initial research of it, it looks like I have to go outside and manually measure the height of an object (...
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0answers
12 views
Calculating SCS curve numbers using DSM instead of DTM
Are the curve numbers (calculated by SCS Curve number method) through DSM (Digital Surface Model) valid? Most of the SCS curve number studies focus on calculating curve numbers through a DTM (Digital ...
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1answer
40 views
Downloading digital elevation model of United States?
I would like to download a digital elevation model of the United States, where can I do this?
It doesn't need to be super detailed.
But it would be nice, if was clipped at the country borders – ...
2
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2answers
64 views
Adding slope values to attribute table (QGIS 3)
I have a DEM raster and some points (one .shp for all points) plotted on it.
I would like to know if there is a way to add the slope value of the pixel that each point is located in the attribute ...
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0answers
17 views
Losing raster quality when using raster calculator (ArcGIS Desktop 10.5.1)
I'm currently working with DEM rasters that I hillshaded. The data I received contain nodata borders, probably the footprint of the originial mosaic dataset. As I received them separately, I can't ...
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0answers
17 views
Stacking lidar-derived height raster as ancillary data for segmentation in ENVI?
I get a a black and white image after following these steps. Does anyone know why I'm not getting a color aerial image beneath the mask?
My setup consists of these steps:
I mosaicked several NAIP ...
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0answers
27 views
Basin Delineation using R
I am trying to get the polygon of a basin boundary using R. I got a 7.5 arcsec DEM that I download from this page: https://topotools.cr.usgs.gov/gmted_viewer/viewer.htm
I look through a lot of ...
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2answers
165 views
Adjacent DEM color matching in QGIS?
I have four 15 arc second resolutions DEM files (15-C.tif, 15-D.tif, 15-I.tif, 15-J.tif) downloaded from viewfinderpanoramas.org. When I input them in QGIS I noticed that the 15-J.tif layer differs a ...
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0answers
35 views
Limiting sharp drop off of coastal DEM raster where there is no data using QGIS?
I'm stitching numerous tiled DEM's using Build Virtual Raster and then 'Align raster' function within QGIS 3.6
Original DEM has no data for sea area as expected:
I get sharp drop off on coastal/...
2
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1answer
51 views
Converting DEM (TIFF) files to terrain files?
I want to create an app to show 3D using ol-cesium. In ol-cesium example it use cesium terrains, But I want to do it with my DEM files.
How can I convert my DEM (TIFF) files to terrain files?
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1answer
29 views
Switching Mars DEM elevation values from negative to positive?
I'm using a DEM of Mars I got from UA's HiRISE website, and I want to convert it into an STL for 3D printing using the DEMto3D plugin.
However, the raster values are all negative, so I thought I ...
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0answers
45 views
Extracting slope of aspect information using QGIS?
In What is SOA (slope of aspect)? @Spacedman explained to me what SOA means. Now I need help to understand how I could work with it and extract the data that I want.
I want to use Qgis (with Grass ...
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1answer
43 views
What is SOA (slope of aspect)?
I’m reading an article that the authors talk about extracting values of SOA (slope of aspect). I can’t find anything related to that on Google.
This article reference is : ZHOU, Yi et al. Automatic ...
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1answer
47 views
Seeking CSMapMaker (QGIS Plugin) equivalent for ArcGIS Desktop?
I'm looking for a tool or script or set of operations to mimic the output from a certain QGIS plugin called CSMapMaker, wherein curvature, slope, and a gaussian filtered DEM are overlain one another ...
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2answers
54 views
Using Ground Control Points in Agisoft Photoscan?
I'm fairly new to the Agisoft Photoscan program, but I am trying to build several models using aerial imagery and highly accurate GCPs, with coordinates collected in the field. I align my photos and ...
1
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1answer
59 views
Raster Volume Returning Wrong Volume
I have a clipped surface using Washington State Plane North (feet) added to a QGIS project using the same CRS. I am trying to calculate the area under this surface (a dirt pile) using SAGA Raster ...
0
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1answer
64 views
DEM not showing when loaded
I'm very new to QGIS, but in the past days I've created 3 different maps. I have now downloaded DEM data in ASC format, and when I open it as a raster file in a new QGIS project there is no problem, I ...
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0answers
12 views
When asked to select raster for elevation (in 3D configuration/QGIS) will be the DEM raster as downloaded or DEM raster re projected?
Do you need to re-project Aster GDEM data from USGS Explorer into a metric coordinate system in order to be able to view a map in 3d mode in QGIS?
Or you just use the file input as it is downloaded ...
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0answers
15 views
Wrong value classification DTM ArcGIS
This DTM has mainly values between 0.7 and -0.7 (see histogram). In QGis it is displayed propper. In ArcGIS (10.5), although the histogram is okay, it displays values in the range between 8 and -8.
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1answer
34 views
Open TIN DEM File format
Anyone know a TIN DEM file format commonly used?
In the context of a TIN DEM generator project, I am searching for a file format to save the TIN generated.
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3answers
63 views
Problem with CRS metadata for UK Environment Agency LiDAR DSM tiles?
I have downloaded some LIDAR DSM composite tiles from
https://environment.data.gov.uk/DefraDataDownload/?Mode=survey
and opened them in QGIS 3.6 with project CRS set to OSGB 1936 (EPSG:27700).
...
1
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1answer
88 views
Resample/Increase the resolution of Digital Elevation Model by QGIS [closed]
I have a DEM of 5m pixel. I wonder is it okay to convert it to 2m pixel? How to do that using QGIS?
And what would happen to the original data, I mean the accuracy? Would it be reliable?
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1answer
12 views
CGIAR DEM converted to XYZ consists of Nodata only
I have a 30-by-30 tile from
http://srtm.csi.cgiar.org/srtmdata/
Later I pre-process as outlined in the previous question CGIAR DEM + gdalwarp -- projection to Cartesian is not happening
(see the ...
0
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1answer
16 views
CGIAR DEM + gdalwarp — projection to Cartesian is not happening
I have downloaded a 30-by-30 tile from
http://srtm.csi.cgiar.org/srtmdata/
Then gdalinfo on the obtained single *.tif-file would yield
Driver: GTiff/GeoTIFF
Files: cut_n30e000.tif
...
