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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Calculating shape_area in ArcMap

I am trying to extract the area of a catchment against Elevation (in classes) [screenshot attached below] The steps I used are: Clip the catchment area from DEM Classify the area in 20 classes ...
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14 views

DEM disappears at certain zoom level in browser

my Qgis2threejs-model looks fine in the plug-in window, but in the browser (e.g. Edge) I have to zoom out to see the DEM. If I zoom in the DEM desappears at a certain zoom level. I don't want this ...
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17 views

Flow Direction tool outputs strange raster that doesn't work with subsequent hydrology tools

My main goal here is to end up with a shapefile that simply defines the ridgeline in a given area. I followed the directions at How To: Identify ridgelines from a DEM and am having some trouble. ...
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17 views

Calculating Cut & Fill amounts for a road, using a feature class representing road and DEM?

I have designed a road centerline in the context of my study area using CAD scripts in python. Then I have converted it to a feature class containing Z-values using ArcPy. Now I need to calculate ...
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11 views

ALOS files contain DEM, MSK, STK files

Can anyone explain to me (in simple terms) under what circumstances one might use the MSK and STK files in my DEM downloads from ALOS? I have used the DEM files but am concerned I might be missing out ...
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17 views

Combining orthophoto and DEM to export xyz-CSV

I have a georeferenced orthophoto and a DEM as tiff-file. For my further workflow I want to export x,y,z (x,y from the orthophoto and z from the DEM). I already managed to create a point layer and ...
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1answer
41 views

Faster, more efficient way to extract stream network from DEM

I am using QGIS and use r.stream.extract to extract the stream lines from a single DEM tile. However, this takes long (about 15 minutes) to complete, especially for a rugged terrain. I plan to extract ...
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1answer
19 views

How to 'cut out' DTM segment

I want to cut out a segment of a DTM - to isolate a river catchment. I would then perform hydrological analysis on the cut out segment - calculate flow direction and so on. What is the best way to do ...
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1answer
26 views

Adding 30 m SRTM DEM to Sentinel-2

I have Sentinel-2 data (13 bands, spatial resolution 10m/20m/60m) and want to add 30 m SRTM DEM to increase accuracy while classification. The composite prepared should be kept at what spatial ...
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27 views

Rendering 3D images from 2+ imagesets + DEM in QGIS

The most general way of rendering a 3D model in QGIS is by using QGIS2threejs. It works by adding a single layer raster-image/orthophoto and exaggerating a DEM, usually a 1 band raster. Depending on ...
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31 views

Plotting the DEM into QGIS 3.10 from the CSV through SAGA

I had troubleshot with creating a DEM in QGIS SAGA, using this example: https://www.geodose.com/2018/09/how-to-create-dem-elevation-profile-qgis.html When I filled up the box as per below: I get an ...
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1answer
14 views

Pixel Size field in gdalinfo command meaning

What is the meaning of the Pixel Size field in the gdalinfo output on a TIFF image? I have 2 images, one is a PAN image (size 400MB) while one is a DEM (size 25MB). Both are in TIFF format. When I ...
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57 views

Extracting physical islands from a DEM

I am working on a project on islands in inland waters in Europe. In the first step I was sorting to large point layers which I got from a state office, trying to identify only points lying on such ...
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32 views

Create terrain profiles with DEM in PyQGIS

I already use the plugin "Profile Tool" to : Draw the profile line Save the line into a point's layer Export the profile png & dxf Then I manualy write the path of the dxf & png into fields ...
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17 views

Incorrect slope values for points in QGIS [duplicate]

I'm trying to determine the slope of sampling points in QGIS 3.4, but the values are all ~89.99°, which I know is incorrect. Pretty sure it's an issue when creating the slope raster. Based on the ...
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56 views

Automating DEM duplication using QGIS

Context: I've imported a DEM of residential composed in several buildings. I've identified the max height of buildings by addind points in a layer for every building. Then I've integer an attribute ...
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23 views

Generate point of view (POV) image inside Digital Surface Model (DSM) or 3D City model

I'm currently working with DSMs (Digital Surface Models) and user perspective inside that model. I'm looking for a Python library, which lets me generate a specific view (from the POV perspective) ...
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1answer
44 views

Obtaining slope and aspect for points in QGIS

I'm new to QGIS. I have GPS points uploaded to QGIS and a ⅓ arc-second DEM (USGS) of the area. I'd like to generate slope and aspect data for each point. What is the best way to do this? The ...
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1answer
46 views

Getting 2 point features with max/min ID from each group with same value in two fields

I'm working in QGIS for a Digital Terrain Model. I've got a table with point features, arguably vertices extracted from multipart iso-curves because the features are provided with a "vertex_par" ...
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1answer
52 views

Is there a tile server for DEM data?

I'm new to GIS and I'm using QGIS 3.4.5. I've been downloading individual SRTM tiles containing DEM data and merging them together in order to see the elevation of every point in a given area (such as ...
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2answers
47 views

Fill a sink with a known volume of water to obtain actual depth and extent of a pond

Using ArcMap 10.7 I have a raster with sinks in a terrain that I developed by processing a DEM dataset. Each sink has been delimited and turned into a polygon too, and its total volume was ...
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3answers
84 views

Using QGIS polygonize tool to create discreet slope polygons

I am trying to create a shapefile with polygons representing areas of different slopes. I am running into some problems using the following workflow. I start with a digital elevation model and using ...
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3answers
146 views

QGIS 3.10 Creating a DEM from CSV

I have been fighting with this for a week or so. I believe I have viewed the related questions on stack exchange, tried some of the suggested solutions that seemed appropriate and have found none ...
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37 views

Creating DEM from contour or point shapefiles in QGIS [duplicate]

I'm trying to make a DEM tiff file from elevation shapefiles that I have in QGIS. I have both contour shapefiles and XYZ-point shapefiles but I can't seem to make the DEM. I've tried using SAGA but ...
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1answer
20 views

Can't join multiple DEMs using QGIS 'Build Virtual Raster' if they span 2 CRS's

I have 20 odd DEMs downloaded from https://search.asf.alaska.edu/ (ALOS PALSAR) Location is the Falkland Islands. Here is an example just adding 2 of the tiles into QGIS which differ in terms of ...
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35 views

Overlap of two images is switched

I try to find a way to create DEM model for two overlapping images from different sources. The upper image has transparency of 50% and as you can see they don't quite overlap correctly. The ...
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1answer
77 views

Line of Sight between sets of two points each

So I have a list of points with their longitude and latitude (Lon_A, Lat_A and Lon_B, Lat_B). I also have a DEM layer from the SRTM for the relevant location. I need to check if line of sight exists ...
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1answer
40 views

Replace value in raster by another raster by ifelse (con) statement in QGIS

Previously I spent a lot of time to see answer on similar question but neither work with my problem. I have QGIS 3.4 and a DEM where I've to substitute more accurate height in cells that are ...
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18 views

Exctract DEM by list of vertex with GDAL

How can I generate a DEM of an area given the vertex list of the polygon that includes it? What I want to achieve is similar to the output of gdalwarp, eg: gdalwarp -t_srs EPSG:4326 -te x_min y_min ...
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62 views

Creating high resolution DEM file from points (path) in google earth using QGIS?

I am having trouble trying to create a DEM file from points in Google Earth. I followed all the steps to export a .kml from Google Earth to then import a delimited text layer that I turn into a .shape ...
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1answer
94 views

How to digitize a feature to include elevation data and interpolate slope in QGIS

I would like to take this archaeological drawing and use QGIS to create a something similar to a DEM or TIN, so that depth/elevation values can be quickly and clearly understood. I do not know what ...
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62 views

Raster map not found error with r.fill.dir

I am new the GIS world and I am having trouble with generating depressionless DEM from lidar elevation data. I am using GRASS 7.6.1 and QGIS 3.4.12. I have used r.fill.dir successfully on a ...
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1answer
60 views

Orthorectifying or Georeferencing aerial photographs

I got 3 aerial photographs from a mountainous area (~3500 - 4000 m.a.s.l), from 1956, 1965, 1977 (no metadata, no camera parameters, scanned white and black). My study catchment is relatively small (1 ...
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44 views

Correcting slope of river bed on DEM using QGIS or ArcGIS

I have a DEM that has incorrect value of altitude/slope in the river bed area. This is a result of the interpolation of elevation value that are close to the river and creates lots of errors. In fact ...
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1answer
57 views

Create polygons from raster with only a selected amount of features (not each pixel a different polygon)?

I am trying to convert a raster into different polygons. The raster is based on a DEM and only contains three classes (each pixel has value 1, 2 or 3, obtained by using the raster calculator). I want ...
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1answer
48 views

How to find elevation profile or elevation changes between two GPS coordinates?

I have GPS coordinates of two locations namely A and B. If I have a great circle path or straight line path between these two locations A and B, I need data of how the elevation changes along the path ...
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2answers
32 views

How to substract 2 dem.tiff rasters through GDAL?

I'm a beginner in GDAL and don't understand the logic of it work completly. I have a folder with 2 DEM-tif files and I need to do this: gdal_calc.py -A D:WORK\gdal\dem05.tif -B D:WORK\gdal\...
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61 views

Is there a way to create a DEM that follow the point cloud so you don't need to clip the DEM after?

I would like to create a DEM from an XYZ file (gridded 0,25x0,25) with 0,25 cell. I'm wondering if there is a way so that my interpolation follows my point cloud, instead of covering a rectangle like ...
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1answer
126 views

Python: Convert DEM to 3D array organized as [lat, long, elevation]

I'm trying to convert a .tiff DEM to a numpy array using python. Ideally the array will store latitude, longitude (or some coordinate alternative), elevation). I'm using Gdal but currently it only ...
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1answer
28 views

How do I convert an elevation shapefile into a CSV file with its XYZ data?

I am new to using QGIS and LeapfrogGeothermal Modeling. I have a shapefile for Elevation and Altitude data and need to extract XYZ coordinates out of it? Can I do that? and how? and what kind of file ...
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34 views

How do I add elevation data to a shapefile in the attributes table?

I'm using ArcGIS to create a DEM/DTM for a viewshed analysis. I have an existing DTM created from UK OS Terrain 5. I'm attempting to add the elevation data to the UK OS Open Map shapefiles for ...
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1answer
28 views

Adding building/woodland elevation data to existing OS Terrain 5 DTM in ArcGIS Desktop [closed]

Would someone be able to give me the stepped process showing how to add building/woodland elevations to an existing DTM raster in ArcMap? I seek this in order to prepare a surface model for a ...
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1answer
71 views

Convert LiDAR GPX to DEM in QGIS?

I'm a water resources engineer with literally zero GIS experience. I'm working as a volunteer on a Engineers Without Borders project delivering safe drinking water to a remote community, where my team ...
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101 views

Slope calculation with GDAL

I compute a slope raster in percentage and then a slope raster in degree from the same DEM with a precision of 5 meters. Why my percent slope raster has a maximum value of 110% (+ 45 °) while my ...
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1answer
26 views

QGIS export DEM to SAGA grid - no coordinate system

I have created a DEM using survey points from a GNSS system. Works like a charm so far. I can extract elevation lines etc. However, when I export it as a SAGA grid it looses the coordinate system. I ...
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22 views

Creating seamless/uniform topography with multiple raster tiles?

I have multiple elevation raster tiles of an archaeological site and it would be extremely useful for me to visualize the topography as one 'uniform' image/layer. I have attempted to merge the rasters,...
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2answers
49 views

Finding date and time of Digital Elevation Model

I downloaded a DEM from the Copernicus site. I can provide the link: https://land.copernicus.eu/imagery-in-situ/eu-dem/eu-dem-v1-0-and-derived-products/eu-dem-v1.0?tab=download I would like to ...
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18 views

Problem with weird values in DTM and not showing correct elevation

I am still new to Gis and don't know if I understand what is wrong. I am working in a ocean survey program with point clouds. As seen on the picture the minimum depth is 1,92 and maximum 12,02. I ...
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28 views

Elevation distribution of protected areas using QGIS

I am using QGIS. Based on a DEM and a vector layer of polygons for protected areas in the Alps, I would like to calculate the areas of the respective protected area polygons in certain altitude ...
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1answer
69 views

Least Cost Path Analysis in QGIS?

For my Bachelor's thesis I try to reconstruct a road betweeen two ancient cities. One method I'd like to try is least cost path analysis with QGIS. I've worked with QGIS before, but mostly only ...

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