Questions tagged [dem]

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

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2 votes
1 answer
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Elevation data from WMS or WMTS?

I am trying (I'm an absolute beginner on QGIS) to basically create a DSM from a WMS/WMTS server, in France. The french institute has several options: https://geoservices.ign.fr/services-web-experts-...
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1 vote
0 answers
13 views

Smoothing a DEM with visible grid

I have a DEM (1x1m) whose hillshade shows like this: As you can see, a grid shows up and that could be a problem for hydrological modeling. Do you know why this happens? How can I remove this grid ...
0 votes
0 answers
14 views

Area of extent changes at when cell size increases

I am working with a LiDAR dataset that has been converted from a set of .txt files into an XYZ point feature, and then interpolated using Topo To Raster. When the cell resolution is set to 1 meter, ...
0 votes
0 answers
53 views

Convert RGB image into 3D Model in QGIS

I'm new to qgis and working with maps in general. I have this image that is technically elevation data (but jpeg with no data points)from Dronedeploy. I imported this image as a raster mesh layer - it ...
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-1 votes
0 answers
8 views

Equivalent to ArcGIS's "Trace Downstream" in open source software (QGIS, Python library, etc.)?

I have a Digital Elevation Model (DEM), which I am doing standard hydrological terrain analysis on, such as calculating flow directions, flow accumulation and watershed delineation. There are lots of ...
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1 vote
1 answer
25 views

Identifying and replacing specific pixel in DEM using ArcGIS Pro

I have a DEM that has a handful out outliers, but I have no idea where they are within the DEM. I'm using ArcGIS Pro and I have used the outlier tool to try to identify the offending pixels, but there ...
0 votes
1 answer
34 views

Float32 to UInt16 terracing problem [closed]

I have the same initial problem as the links below, but I cannot change to using float32 as I am not using Blender. Terracing / stepping artefacts after converting lidar DTM from float32 to uint16 ...
0 votes
0 answers
9 views

Reading EU-DEM using geotiff.js to a 2d height matrix results in wrong pixel resolution

I am reading a EU-DEM v1.1 geotiff file downloaded from copernicus website using geotiff.js package with the following code : const geo = await fromFile(this.demFileUrl); const image =...
0 votes
1 answer
31 views

Terracing and data format issues when converting DEM from float32 to UInt16

I have spent quite a bit of time trying to figure this issue out; I was hoping someone on here could give some advice on what to do. I am having issues with terracing on my 3D model in Blender and I ...
0 votes
0 answers
94 views

Extracting 3D model of tree canopy shape and landscape from LAS files

I have been trying to find a way to convert LiDAR data into 3D models that show a detailed landscape including the tops of trees and other structures such as buildings. So far my attempts have ...
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1 vote
0 answers
25 views

DEM to Slope in QGIS 3 [closed]

I'm having trouble with the slope of this particular DEM (USGS_13_n33w097_20211124). The file downloads correctly and presents the elevation values in QGIS, however after running the QGIS Slope tool, ...
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0 votes
0 answers
29 views

Why does the SAGA Wang & Liu fill sinks algorithm decrease elevation values of my original DEM?

I used the SAGA Wang & Liu fill sinks algorithm to create a depressionless DEM. Apart from filling depressions however, the output also generates decreased DEM values of the original dataset. The ...
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-1 votes
1 answer
38 views

Getting high resolution DEM for a location [closed]

As a part of my project, I want high resolution (10m approx) DEM for my desired location. How and where can I get it? I already tried with 30m DEM obtained from USGS. I am getting blurry DEM, if I ...
1 vote
0 answers
30 views

Slope Angle between vertices using QGIS

I am trying to work out whether a center pivot irrigator (you may have to google this to see what they look like) has too much angle between the spans as it goes over hilly terrain. I can generate ...
0 votes
0 answers
31 views

Getting blurred image after extracting AOI through shapefile from USGS data

I intended to generate DEM of required location using ArcGIS Pro. Using USGS Earth Explorer, I downloaded the SRTM DEM as a .tiff file for a huge block of area which consists my desired area in it. ...
0 votes
0 answers
13 views

MATLAB code not returning result

I am completely new to MATLAB and coding. Why is not the following code returning me an .asc file? I am sorry if it is too large, I am just trying to solve it for 2 days and I can't figure it out. The ...
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2 votes
0 answers
26 views

Calculating upstream (contributing) area for >10,000 points using Python

I would like to create polygons of the contributing area for > 10,000 points. I have all information that I need for this, including a 30m DEM, a river network (LineString geodataframe file) and ...
  • 151
1 vote
0 answers
26 views

QGIS: save DEM from xyz-tiles returns area with unrealistically low raster values

Newer QGIS version (I use 3.26.2) come with pre-installed XYZ Tiles connection Mapzen Global Terrain: a worldwide digital elevation model. For local use, I donwloaded a section of it (right click ...
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1 vote
1 answer
52 views

Converting .obj (3D files) to .tiff raster

I have a 3D .OBJ file that i need to convert to raster (geotiff) so that i can use it in QGIS/python gdal. I have found several answers online about how to convert a DEM or TIFF to .obj, but not the ...
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0 votes
0 answers
20 views

Average altitude when DEM is just partially covering some areas

I have a shapefile regarding the centroids of Europe and a raster related to the Euro DEM: the aim of my analysis was to compute non-overlapping buffers and extract the average altitude from them with ...
0 votes
1 answer
33 views

Extracting shrubs from DSM

I want to find to find single entity shrubs. I thought I could use a DSM and DTM, though, it seems like it is only possible to find trees (since the trees are covering the shrubs)... Is there a way to ...
0 votes
1 answer
20 views

Accuracy of LIDAR from XYZ and DEM comparison

I'm taking point cloud xyz's from LIDAR and turning them into DEMs, then comparing that DEM, to a DEM of the original 3D CAD Models to see how well the LIDAR is measuring the model for elevation and ...
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2 votes
1 answer
27 views

Google Earth Engine - Blend Error

I have two different DEM images that I am trying to blend. The first is based on SRTM (DEM1) and the second on coastalDEM (DEM2), with different but overlapping areas. When I do var DEMblend = DEM2....
0 votes
0 answers
38 views

Processing a LiDAR image to be more detailed

I'm using ArcMap 10.8 to try and find old roadbeds. The DEM data I downloaded is very dark and shaded. You can't see anything at lower elevations. I have the hillshade effect turned on but you can't ...
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0 votes
0 answers
38 views

Unwanted line in the raster data (DEM and DEM derived indices)

I am getting unwanted parallel lines in the raster data (see image). I was deriving different indices like slope, terrain ruggedness index, topographic wetness index etc. Prior to calculation I also ...
0 votes
1 answer
21 views

How to stack layers (slope, curvature, aspect, etc) derived from DEM to form multi-band images in QGIS?

Made a DEM from Landsat imagery and derived the aspect, slope, curvature, TWI, etc layers (generic flood conditioning factors). I now need to incorporate these layers and feed them to a LSTM neural ...
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0 votes
0 answers
50 views

DTM hillshade function error: 'does not exist in the file system, and is not recognized as a supported dataset name'

I am trying to use the hillshade function in QGIS 3.24.2-Tisler. I downloaded a DTM from https://app.pdok.nl/viewer/ as an WMTS. When I try to use the hillshade function I get an error (see below): &...
1 vote
1 answer
28 views

Convert points with x,y coords and value from to a raster image

I have a CSV file with xcoord,ycoord and pixel value from DEM. After I import it in QGIS, I take this table. I want to make a raster from this point layer. I tried rasterized (vector to raster), I ...
0 votes
0 answers
17 views

IBERAULA - DEM file not working

When using Iberaula, I'm trying to use the data from Defra or OS Terrain 50 as this is UK data. However, I'm trying to import the DEM data through RTIN > Create RTIN > Mesh and import the DTM ...
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3 votes
0 answers
46 views

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 ...
0 votes
0 answers
32 views

Creating slope map from DEM of Lunar South Pole

I've managed to create slope maps from other DEM's without much issue, but this DEM seems to have trouble and only does the very top section, with the rest being an error. I am very much a beginner in ...
  • 1
1 vote
0 answers
59 views

Python library for hydrology calculations for multiple points

I have a DEM (TIFF) with multiple points, which mark wells (right term?) of an underground pipe network: I was wondering if there is a Python library which uses the elevation of the DEM to generate a ...
  • 89
4 votes
1 answer
116 views

Number of pixels Elevation - Aspect - Slope

I have a DEM, resampled at 100 x 100 and clip by mask with a polygon. Unique values report give me Total pixel count: 733810 with NODATA pixel count: 427098. Aspect and Slope map give me the same ...
0 votes
0 answers
18 views

Apply fix value difference in selected pixels of a raster file in Qgis

I am using the serval plugin in QGIS to spot edit a DEM in raster format. Besides the built in tools that I use, I have realized that in some cases I can achieve the desired results by applying a ...
  • 1
0 votes
0 answers
28 views

Drainage line do not match DEM stream line using Arc Hydro

I've been running my DEM using Arc Hydro, drainage line output do not match the DEM or the basemap stream. What could be the problem? The red line is my stream from delineated DEM, the blue line is ...
0 votes
0 answers
17 views

Point value Change after projection - USGS DEM Raster VS Imagery Layer from Esri

I'm working on a project that requires National level DEM data, and Esri are providing the imagery layer (https://www.arcgis.com/home/item.html?id=0383ba18906149e3bd2a0975a0afdb8e). For the most part,...
1 vote
0 answers
38 views

How to ignore -3.4028235e+38 as a minimum value in a DEM?

I am working with a DEM with the range of 99.93-169.32 (This range can be seen in QGIS). I am trying to open this DEM using cv2 or rasterio in python, and after that apply some filtering methods to ...
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0 votes
0 answers
29 views

DEM from Sentinel 1 C-band SAR

I have been using the standard protocol (ESA/ASF) to generate DEMs (actually DSM which is what S1 C-band gives) from Sentinel-1 C-Band SAR tiles. My locations are in the Eastern Himalayan foothills (...
1 vote
1 answer
41 views

Calculating area's region in DEM

I have a DEM map in my project Tsunami Assesment project.The white area below the mentioned map is sea and we know that possible tsunami height is 14 meters(please neglect the line, there is an error ...
0 votes
0 answers
36 views

Merging DEM with polygons/lines

I want to connect my DEM (digital elevation model) with the map which was divided into polygons/lines. I am analyzing tsunami events in my project. I have the following documents: one of them contains ...
0 votes
1 answer
34 views

QGIS raster calculator returns non-sense low number

I have a raster with depths (ESRI ASCII DEM format, named "combined_smooth") from "-5" to "6" (positive values are depths, negative land heights). I want to increase the ...
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0 votes
0 answers
11 views

When combining rasters how to reduce heights of regions having height above a limit in ArcMap?

I am trying to use DEMs extracted from USGS earth explorer, in my DEM there is a plane region (Ganga Planes) adjacent to high mountains (Himalayas). While combining DEMs of that region I want that if ...
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0 votes
1 answer
50 views

LAS2DEM QGIS No Results

When I try use LAS2DEM in QGIS, the results are an empty file: I have followed all setup instructions with the LAStools zip folder (in a C:\ with no spaces or special characters in the path, and set ...
  • 1
0 votes
0 answers
117 views

Problems with phase unwrapping unsing SNAPHU

I am trying to generate a DEM using a pair of Sentinel-1 images by following this tutorial. I am running into the following problem in the Phase unwrapping step using SNAPHU. There are some noticeable ...
1 vote
1 answer
33 views

Calculating terrain attributes before or after upscaling DEM

This is more of a theory question. I am working on a project that requires the use of topography data, I have a 1KM resolution global DEM to which I will be using GDAL to calculate general topography ...
0 votes
0 answers
56 views

Adding z dimensions to a Polygon

I have a polygon (vector file) which has a base z location from a raster file, however it is still a flat shape. Is there a way I could add a z dimension to this vector file so it covers a 3-...
0 votes
0 answers
54 views

How to get the elevation value of a specific location from DEM using GeoServer

I am trying to understand how and if it is possible to get - extract the elevation value of a specific point (given x,y values) from a DEM layer in the GeoServer. The only values that i am able to get ...
0 votes
0 answers
31 views

Classify which cells were uphill and which were downhill when calculating Tobler's Hiking Function

I am using the ArcGIS Desktop (10.7.1) Path Distance tool and a table and DEM to calculate the cumulative time to reach locations. Is there a way to track and map which cells were downhill and which ...
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4 votes
2 answers
145 views

Extract Single (or small number) Contour from DTM data in QGIS

I understand that Contour data can be extracted at particular intervals fairly easily, but have been recently mapping a number of Flood Water Design levels which are denoted to the nearest 0.001m. It ...
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0 votes
0 answers
19 views

QGIS - Avoid DEM cells where no vector contours when using TIN

I'm using QGIS TIN functionality to create a DEM (image attached) from vector contours (image attached). I have set the TIN to Attribute Type = 'Break Lines' and the Interpolation Type = 'Linear'. My ...
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