Questions tagged [dem]

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

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21 views

R lidR package grid_terrain() giving weird plot

I am working on the pre and post lidar earthquake data from Kumamoto, Japan. I would like to generate a DTM with the grid_terrain(pre_online, res = 1, algorithm = knnidw(k = 10L, p = 0.5)) function in ...
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18 views

How to measure rate of mass movement? [closed]

How would you use DEM to measure rate of mass movement? I can work out volume change by using the raster calculator to minus one year DEM from another but how would I turn this into a rate of mass ...
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1answer
28 views

Issue with delineation using dem because of a DAM

I have a high-resolution DEM which I use it delineate watershed. I am getting the delineation like this The main branch is not getting delineating till the source. So I used a hillshade to check the ...
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1answer
56 views

Merge overlapping polygons to elevation data

I'm new to GIS and need to create a shortest path avoiding buildings. The buildings are represented as polygons in a shapefile. In QGIS I created a buffer polygon for each building, corresponding the ...
2
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1answer
29 views

How does QGIS calculate slope?

There are several ways to calculate slope in qgis using a DEM layer, but how does it actually work? My results show pixels with a slope of 40°+, this seems like a lot (in my DEM, one pixel is 25*25 m)....
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23 views

Slope calculated with QGIS vs slope in GoogleMaps

I want to calculate the average slope in percent of a vector line in QGIS. I have a DEM layer, converted it to a slope layer and then I use the plugin Profile Tool to calculate the slope of the line. ...
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19 views

Is there a way to batch resample and mosaic/merge many large raster files at once?

I have over 400 large raster DEM files at 1 m resolution that I need to resample to 10 m resolution and merge/mosaic them all into one file. I am wondering if there is a way to do this all in one step ...
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1answer
44 views

How to smooth the DTM?

I had a point file of an area around 70 km^2 collected through field survey using Auto Level. The survey was carried out in the lines 25 m apart. I converted the readings from auto level into point ...
3
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1answer
42 views

Detecting cliffs higher than X meters from DEM

Using QGIS, and the 'Raster > Analysis > Slope' tool, I could easily detect cliffs from my DEM. I can identify all cliffs, and can color areas where slope is above a certain threshold. Since ...
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1answer
34 views

Failing to open a raster (TIFF) in QGIS

I have a raster that I can't open in QGIS. When I load the raster, I get the following message: CRITICAL Capa no válida: GDAL provider cannot open GDAL dataset C:\Users\Name lastname\Destktop... ...
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0answers
14 views

Edit single pixel in ASCII grid

I converted DTM Data from LAZ to ASCII. Now I got some artifacts with an obviously wrong cell values. Is there a simple way to edit just a single cell? I tried looking for the cell value in Notepad++, ...
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0answers
37 views

Extracting ridges and peaks in QGIS

Is there a way to extract mountain ridges in QGIS? I have been trying to use the Valley and Ridge Detection SAGA tool, but it freezes for hours and I am wondering if there is a faster or alternative ...
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7 views

How to save the raster file with the elevation data and convert to a asc/dem in arcgis pro?

Beginner arcgis pro user here... I have subset and digitized a satellite imagery and I have the ground elevation data (first image). How do I save the data (integrated with the elevation) as a an asci/...
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1answer
58 views

Extracting specified elevation value from mid point of valley along cross section based on DEM using ArcMap

I am using ArcMap. I need to extract the intersection point of the cross section line (blue line) where it intersect with the height variation value of 5m in both sides of the section from the mid ...
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0answers
24 views

DEM water body visualisation (QGIS): extract areas with a min amount of pixels with the same value (= water surface)

I want to create a background map of a DEM (1m spatial resolution) to show the study area. The study area (Northern Germany) contains many water bodies. I have problems with the visualisation of these ...
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0answers
18 views

GDAL Slope function not working with SRTM DEM data?

I'm a QGIS rookie trying to generate slope data for research projects in South Africa. I've managed to download DEM data from Bing Aerial maps using the SRTM-downloader but cant get the GDAL slope ...
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0answers
27 views

Export DEM as point cloud in LAS format

I have a huge Digital Elevation Model in AutoCAD Civil 3D. I used the NNI smoothing method on the DEM (with 0.2 meters raster). I want to export the surface data as a point cloud in the LAS format. ...
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0answers
19 views

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....
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1answer
45 views

Converting contours to DEM raster (using TIN interpolation)

I have a contour file for the Brazilian state of Rio de Janeiro (available here https://www.arcgis.com/home/item.html?id=c575d42b3f114d7da4784a337b42dcd9) and need to convert it into a DEM raster file....
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1answer
25 views

Adding Z (DEM) to my X and Y table (CSV) in QGIS

I have CSV with Name (ID), X and Y. Also have DEM. Hoping to combine my CSV that has Name with corresponding X and Y, then add the Z from DEM. "Join Attributes from Location" and "Point ...
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0answers
41 views

Calculating height above ground from ellipsoidal height and GDEMs

I'm very much a novice on GIS/geospatial related work. Recently I've been trying to find the height of a 3D coordinate (latitude, longitude, altitude) above the surface of the earth. I have measured a ...
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0answers
44 views

Merge raster layer error, illegal size

I have an issue with merging several tiles. I am loading the original XYZ files into QGIS (works fine) and try to merge them afterwards yia Raster/miscellaneous/merge . If I only merge 2 tiles this ...
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0answers
11 views

Export a DEM as a SDTS file in QGIS

I am trying to export a DEM from QGIS into a SDTS format for somebody to open it in SketchUp. Anyone has any ideas? My understanding is you can do it in Arc, but I don't have an Arc license. Sketchup ...
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0answers
45 views

How does a GeoTIFF file store elevation data?

I'm trying to understand how elevation data is stored in GeoTIFF files, when used for Digital Elevation/Surface Models. My very basic understanding is that in a GeoTIFF file (or at least those ...
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25 views

Cut-and-fill, will my method output a valid result asumming absolute DEM accuracy?

I'm using QGIS and have to calculate the cut-and-fill volume given a new topography profile. Right now, I have both elevation data (old and new) in DEM with projected CRS. I've tried using zonal ...
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0answers
20 views

Creating Standard Deviation Index (SDI) cell by cell in DEM

I am fairly new to QGIS and have been struggling to find a solution. To put it simply I am trying to find a way to display the Standard Deviation Index on individual cell basis by comparing it to its ...
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1answer
42 views

Seeking tool to generate topographic profile from points

I'm trying to generate a topographic profile, but not the typical terrain profile. To do this, I generate a grid of points uniformly distributed on a surface of a DEM. From these points (from which I ...
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1answer
32 views

How to make DEM that is non-contiguous?

I am an amateur trying to produce a DEM that matches a map from the 1960s. I have succeeded in georeferencing the map and aligning it with a DEM, but I do not know how to make the DEM emulate the &...
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1answer
18 views

nDSM tree detection using scipy watershed

I am trying to generate segments with single trees in a normalized surface model (nDSM). I tried using scipy.ndimage to achieve this, but the segmentation results are not precise. I would like a ...
1
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1answer
38 views

Expanding river width on raster based DEM in ArcMap [closed]

How do I expand the river width on a raster based DEM in ArcMap? For example, my DEM has 20 m cell size, and I want that my river is wide 3x that everywhere (60 m in total, or 3 cell wide). I have ...
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0answers
23 views

Statistical difference in DEM-height compared to a specific point(feature)

Recently I've been struggling when trying to compare surrounding points of a DEM to a specific one (a feature in my case. A castle to be precise). I want to find out how steep a slope in an area ...
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0answers
23 views

DJI Phantom 3 Pro [duplicate]

I want to use UAV to get digital elevation model for geomorphological researching and, while trying finding suitable UAV with reasonable price, I found out DJI Phantom 3. More over, I found it very ...
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1answer
17 views

How to get elevation raster data at custom scales for a specific region?

I'm new to GIS and trying to obtain elevation data for a specific region, transformed to raster data with a custom cell size of 10 meters. My first attempt was to download a TBDEM dataset from USGS ...
3
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2answers
81 views

Extracting a DEM without low vegetation cover in a flooding area using LiDAR data

I've been struggling with this for the past few days. I want to create a DEM of a flood control area, which is covered in low/intermediate-height vegetation (pioneers and reed mostly). The point cloud ...
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1answer
43 views

Manually changing elevation data of DEM using QGIS [duplicate]

I'm looking to do personal modifications to a DEM (Aster global elevation model). I want to select an rectangular area & reduce its recorded elevation by 20m. There are other parts on my map I ...
2
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1answer
47 views

Indexing RasterStack in for loop

I am trying to calculate canopy height. I have a RasterStack which has 8 rasters in it. The first 7 are DSM; the 8th is DTM. As you see in the function, I need to subtract every DSM with the same DTM. ...
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0answers
27 views

Calculating mean of true ground points in every pixel of DEM using ArcGIS Pro

I have a DEM of 12m resolution and true ground points (more than 11,0000 points) to assess this DEM. I want to take the mean from all points within every pixel using ArcGIS Pro. How can I do this?
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21 views

Clipping raster error 4

I'm on QGIS 3 and have used the 'AusMap' plugin to upload google maps raster images and a 5m LiDAR DEM. I have created a shapefile (polygon) and now I want to clip the raster files to the extent of ...
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0answers
31 views

Raster reprojection from EPGS:4269 to EPSG:4326

I downloaded dem rasters for USA and they use EPSG 4269 CRS. Now, I want to sample raster values (elevation) at some points that use EPGS:4326 CRS. Do I need to reproject rasters to 4326 before ...
2
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1answer
47 views

Get footprint or boundary of LIDAR data

I am using the lidR package in R to manage my ALS data. I was having problems generating DTMs on the edge files of my catalog because the tool lidR::grid_terrain() was doing some interpolation between ...
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0answers
49 views

Calculating slope between two points

I want to know slope value between two point with lat and long coordinates. I can also get DEM values at lat long location for both points. What should I do next in order to calculate slope?
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0answers
18 views

Slope calculation workflow on pixel level

I know I cam calculate slope values based on DEM raster but I want to know how slope is calculated on pixel level. What values are taken into account when calculating slope on one pixel? Can anybody ...
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0answers
16 views

QGIS: creating TIN from raster with a specific point density per m²

I have an elevation data from Laser Scan with 8 points/m2 density. To lower the computation time (and to transfer it to another Software) I want to create a TIN file with density of 0.5 points / m². ...
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0answers
14 views

TauDEM flowdircond tool doesn't give an output

I'm using the flowdircond tool from TauDEM to create a hydroDEM. The tool gives an error message when using mpiexec through Windows CMD. When used without mpixec, the tool doesn't give either the ...
2
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2answers
30 views

Unit conversion of DEM

I have a 10-m resolution DEM, in the form of a .gdb. The "Value" field is in feet and cannot be edited. I am working with SWAT -- which uses the Band 1/Value field-- and assumes units are in ...
1
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1answer
15 views

Feature extraction for sand dunes and hills using DEM

I want to extract only sand dunes, ridges and hills from a DEM. Note that there are other elevated objects in the DEM as well and on the mountains and ridges that I don’t want. Is there any way i can ...
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0answers
8 views

Overlay Vector Layer on 3D model built from another Vector Layer

I have 2 vector layers. One vector layer has data that I built a 3d model from. I built a choropleth from the other vector layer. I want to overlay the choropleth layer onto the 3d model built from ...
1
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1answer
85 views

Failing to download SRTM data from USGS

I was used to download SRTM/DEM data from the following link: https://dds.cr.usgs.gov/srtm/version2_1/SRTM3/ But I'm not being able to download anymore, I don't know the exact causes of that, it was ...
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0answers
48 views

Dynamic Slope Calculation on ArcGIS Online Web Application

I have a DEM raster layer in our own GIS portal. It is then included in a web map online from which a web application is created. I am looking for a way that would allow users to calculate slope by ...
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0answers
15 views

Classifying DEM base on lowest elevation of stream generated by flow accumulation of same DEM using ArcMap

How do I classify a DEM base on the lowest elevation of a stream (stream generated by flow accumulation of same DEM)? I want to find those elevation of DEM that are close to the floor of the stream. ...

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