Geographic Information Systems

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For questions about Digital Elevation Models (DEM), Digital Terrain Models (DTM) and Digital Surface Models (DSM)

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Differencing two rasters with very different resolutions (QGIS 3.20.3)

I am having a problem with analysing two rasters with 2 significantly different resolutions. Background on the two rasters: DEM is the ALOS_30m DEM which is in the WGS_84 format. Merged together ...
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0answers
17 views

Missing some data from query in PostgreSQL

I am using this query to get elevation data from PostgreSQL: WITH points(geom) AS ( values (ST_SetSRID(ST_Point(980279.44, 6431129.89), 2154)), (ST_SetSRID(ST_Point(982573.24, 6429308....
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0answers
13 views

DGM1, virtual raster error

I want to create a virtual raster with DEM1, existing of 133 tiles (QGIS 3.18.3). It show following processing warning: GDAL command: gdalbuildvrt -resolution average -separate -r nearest -...
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1answer
27 views

How to interpret Terrain Ruggedness Index according to Wilson et al. (2007)?

Is there a categorical scale used to interpret values from the Terrain Ruggedness Index as calculated by Wilson et al. (2007), which is used in the raster library in R?
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36 views

Comparing polylineZ elevation to DEM at various points along the line, not just the vertices

I have a polylineZ feature that represents sewer lines. I am looking for areas where points along the line may be above ground elevation, representing aerial lines. The problem is that I need to ...
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0answers
13 views

Extracting elevation data from DEM with Python [duplicate]

I have downloaded a DEM model for a given region. I use rasterio like this: import rasterio dem_path = 'path_to_dem.TIF' list_of_points = ((42.136097, 24.742168),) def get_offline_elevation(...
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0answers
50 views

Using a DSM and DEM together to identify height above ground

A pretty basic question I feel, but its something I thought I understood and further reading has caused more confusion. DEM is the topographical/elevation of the ground. DTM and DSM are pretty much ...
1
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1answer
62 views

Creating theoretical landscape using QGIS

I would like to create a series of random theoretical landscapes (DEM) of the same size with certain parameters ranges (e.g. slope range, elevation range) and ideally with the option of defining the ...
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0answers
27 views

Interpreting Ruggedness Index calculated from SRTM Tiles

I am looking for help interpreting the values from Ruggedness Index calculations. I downloaded SRTM tiles using the SRTM Downloader plugin in QGIS. Then I calculated ruggedness from SRTM tiles in QGIS ...
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0answers
14 views

r.fill.dir not working

I am using QGIS 3.16.2 "Hannover" with GRASS 7.8.4 on Windows 10 64 bits. Im doing a watershred and r.fill.dir is not working, the message is the common the following layers were not ...
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3answers
34 views

Adding height from xyz-layer to points in Vector layer in QGIS

My task is to put the height from a DGM1 model in Germany to some points on an other vector layer with attribute table. I don't know how this possible. Any ideas?
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20 views

Which conversions/transformations does GDALs ReadAsArray() use (for GeoTIFF DTM)

I have a bit of a complex problem. The big picture: I want to convert a GeoTIFF DTM to a 2D "Image"/matrix where the value of each pixel represents the height. Later I want to read the ...
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0answers
36 views

Seeking U.S. Digital Terrain Models (DTM) to download

I tried to google using keywords like DTM or Digital Terrain Models. But there is no website that could supply DTM. I want to download DTM from these states: GA, TX, AR, LA, FL, SC, NC, MS, AL, SC. ...
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1answer
34 views

Raster is in the wrong place, upon warping it dissappears in QGIS [duplicate]

I assigned a Raster image to its designated projection, it reappears 500 miles away. I tried to assign different projections, it goes off to another random place. I reproject it a variety of CRS's, ...
2
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1answer
96 views

Rotating raster using Python

I am trying to rotate a DEM raster (NetCDF file) using Python language, but there is still no progress. I have tried GDAL Python but not so much information in the document about rotation. Do you know ...
1
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1answer
47 views

Batch Processing Contour Lines in QGIS

I'm trying to create contour lines at 40 meter intervals from 60 different DEM Contour Shaded files. Rather than doing them 1 by 1 I have tried using the batch process but I don't get any results as I ...
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0answers
24 views

Ellipsoidal to Orthometric Height Conversion

I have two DSM, one generated using lidar data in NAVD88 and the other I produced using stereo images in WGS84 G1150. I am trying to covert G1150 to NAVD88. I have tried a few conversion tools, ...
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0answers
9 views

Thinning produces discontinuous streams

I am working on GRASS GIS 7.8 and I have been able to derive the accumulation, streams, and basins from a DEM using the r.watershed command and the documentation on the GRASS website. The process of r....
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1answer
13 views

Identifiying the levels for streams derived from DEM

I am using GRASS GIS and I have been able to identify the various water-flow channels / streams using the documentation from r.watershed. Now I wish to identify the levels of the streams. For example, ...
2
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1answer
41 views

Converting DEM raster (NetCDF file) into point cloud (LAS file) using Python

I would like to convert a DEM raster NetCDF file (*.nc) to point cloud LAS file (LAS/LAZ) using Python language. I have been doing the research but still don't have a result. I also have a look on ...
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0answers
15 views

Add viewshed values

I have multiple cumulative viewsheds made with the visibility analysis plugin. I would like to combine them together by adding their pixel values. In qgis, I can select different pixels and get the ...
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0answers
22 views

Finding slope of polygon using ArcMap

I am using ArcMap and I am trying to find the slope of a polygon. I have a polygon of Cyprus which consists of all parcels of land. Then I have the DEM for Cyprus from where I can find the slope. From ...
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0answers
31 views

DEM color ramp settings, disabling continuous legend, label precision with PyQGIS script

I have a script to automate my workflow in QGis. substring = "_DEM" strings_with_substring = [name for name in names if substring in name] for i in strings_with_substring : DEM = ...
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1answer
57 views

Calculating average elevation from given points layer and DEM

I am using QGIS 3.18. I have a point layer showing population estimates at the administrative center points and an aster digital elevation map. I'm trying to calculate the average elevation of these ...
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2answers
97 views

Convert DSM to DTM and nDSM

I have some DSM GeoTIFF files and I want to convert them to DTM and then obtain nDSM by subtracting DTM from DSM. Is there any way to do it? I want to apply this to several different DSMs so it's best ...
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0answers
50 views

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 ...
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0answers
19 views

Continuously receiving NoData as Raster tool output

I'm running ArcGIS Desktop version 10.7. I'm working with a DEM and DSM, both from the same municipal data source (not prepared by me). I am attempting to do some simple analysis on both of these such ...
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1answer
28 views

Denoise/smooth DEM in GRASS GIS using r.denoise addon

I'm trying to denoise/smooth a digital elevation model (TIFF) file on GRASS GIS using r.denoise add-on. I cannot get it to work. I don't know what to enter in the output box, my goal is to create a ...
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0answers
27 views

How to extract source headers from gdal WMS driver?

I am using gdal.Warp and Mapzen Terrain Tiles in Python to generate arbitrary digital elevation models. I see in the Terrain Tiles Documentation that the Mapzen Terrain Tiles service will return a ...
2
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1answer
56 views

Elevation data in the same spatial reference (WGS84) between dem and icesat2 point data is offset by ~30 m

I have a specific problem re: projected coordinate systems. I am working with point data from IceSat2 and a LiDAR-derived DEM of Daviess county in Indiana. I am trying to compare height values for ...
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1answer
33 views

Clipping DEM to bigger shapefile extent in QGIS

I have a polygon shapefile that is bigger in extent than my DEM. I want to clip my raster dem to my shapefile and fill missing space with NoData. I have tried clip raster by mask layer as well as by ...
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1answer
41 views

Converting a degree slope raster to a percent slope raster, without a DEM, using raster calculator

I've been given a raster of degree slope which I need to convert to percent slope. As the original DEM is not available and those who provided the raster want me to work with this one, I have to ...
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1answer
23 views

Why does no interpolated line appear when I use the 3D Analyst to generate a elevation profile in ArcMap?

I want to generate an elevation profile based on a DTM with ArcMap 3D Analyst but the program does not show the the interpolated line. I did the following steps: Opening 3D Analyst, adding a Digital ...
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0answers
46 views

Converting GeoTIFF to PNG results in completely black image

I have a set of DEM tiles (TIFF format) retrieved from https://cteco.uconn.edu/data/download/flight2016/index.htm which I would like to convert to 16-bit PNG format so that I can use them as ...
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0answers
39 views

gdal_contour: Specifying index contour lines

I'm building an application where I need to programmatically generate contour lines(and export to a .dxf) from a raster terrain data-set(DTM specifically). What I've tried: Using gdal_contour, I've ...
4
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0answers
45 views

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 ...
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0answers
24 views

Manually create a DEM from survey data

I would like to create a DEM for a parking lot catchment, so that I can model surface water runoff paths in ArcGIS Pro. I have raw elevation survey data, collected at grid line intersections across ...
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0answers
65 views

Use BIGTIFF=YES creation option. NOT WORKING

I am busy trying to merge 62 DEMs (totaling in 5.6 GB and in GeoTIFF format) in QGIS 3.18 to create a single DEM of southern Africa. The problem was that the tiff I was trying to generate was larger ...
1
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1answer
37 views

Creating raster stack from two raster layers

I have two raster layers that I would like to create a raster stack from. They are currently in different extents. One is a DEM layer and the other is a raster of an individual's home range. This is ...
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0answers
17 views

ArcGIS: Viewshed analysis with multiple observer points

I am trying to do a viewshed analysis with a DEM and multiple observer points. What I am trying to achieve is, that the tool counts the pixels which are visible from each observer point. I am a bit ...
1
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1answer
27 views

Calculate TPI for irregular DEM

When I use SAGA's Tool Topographic Position Index (TPI) or Tool TPI Based Landform Classification (in QGIS or SAGA itself) on a rectangular DEM the results are as expected but when I try them on a DEM ...
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0answers
18 views

Repeating DEM Color Ramp at Set Intervals using ArcMap

I have a Copernicus DEM file. I want to represent the elevation data with a color ramp, but instead of using a single color ramp to represent the entire range of values, I would like to repeat the ...
0
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1answer
84 views

Calculate orthometric height with geoid ITRF97 and ellipsoid WGS84

I'm trying to calculate the orthometric height between ITRF97(or EGM96) and wgs84 (or grs80) in specific latitudes and longitudes. For example: in longitude 57.111 and latitude -5.582 i used an online ...
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0answers
29 views

Aster DEM indexing open-data-cube, Cube in a box

I am working on Cube-in-a-box, local installation, and want to index Terra Aster DEM data. If anyone has worked on these, can someone share the preparation & indexing script or guide me for the ...
1
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1answer
87 views

LiDAR 3D modeling using package rayshader and LAS file in R

The rayshader package in R allows beautiful 3D modeling in R. Now I was trying to first try and overlay a LAS file on top of a base-map which is a Rayshader array object. I was trying %>% to link ...
3
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1answer
72 views

Publishable quality 3D figure from QGIS

I tried to make a 3D map by overlaying Google Earth image on a DEM using an inbuilt 3D map feature in QGIS. Also, using qgis2threejs plugin. But I want to export the final figure to a publishable ...
0
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1answer
46 views

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 ...
3
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2answers
42 views

Creating singleband pseudocolor ramp displaying colors based on values using QGIS

With QGIS desktop, I'm trying to create a ramp to a DEM using a singleband pseudocolor style. I have created a ramp with 15 different colours and values as well. I can't find the option to apply those ...
2
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1answer
38 views

Aligning visible light data to DEM

I just want to preface this by saying that I am not a cartographer, geographer or GIS professional, I just recognize that this is probably the best place to ask my question. As I am none of those ...
2
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1answer
48 views

Precise landmass outline from DEM data with QGIS

I can't find a way to obtain the following (see picture below) from DEM data with QGIS -- that is, an image that would show the landmasses as white and the oceans as black from DEM data. I've also ...

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