# Questions tagged [dem]

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

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76 views

### Coarse Woody Debris extraction

I created very high dense point cloud of some forest plots using terrestrial laser scanner. Then removed points above 1.3 meter to see the coarse woody debris (Fallen dead trees). Attached is the ...
185 views

### Computing the horizon profile given a DEM in python

Can anybody orient me towards an open source python script that computes the 360° horizon profile (azi + elevation of highest topography in eye sight) from a single point (x,y,z) on Earth (account for ...
148 views

### Use DEM elevation attributes in vector polygon?

I am modeling glacier retreat scatching polygons on DEM surface trying to come out with 3D scatch. Is it possible to adjust "height" of polygon to follow elevation of DEM surface (eg. glacier height ...
477 views

### Computing the slope of a road using DEM

I work with QGIS 2.14 and I want to create a map of road network showing the slope of each road with at least this scale: <3%; 3-5%; 5-7%; 7-9%; >9%. I already have a vector layer of roads and the ...
68 views

### Refining DEM with topographic survey?

I have a DEM that is based on LiDAR and I would like to refine a small area of the DEM with topographic survey points. Is there a good way to do this in QGIS?
165 views

### Watershed delineation with meandering river?

I'm using ArcGIS (Hydrology toolbox) for watershed delineation for a number of pour points, and I'm running into problems with very meandering rivers on extremely flat alluvial land (Amazon basin). ...
56 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 ...
56 views

### Problems with DEM exporting after Elevation Void Fill function use

I filled nodata values in DEM by Elevation Void Fill function, everything was ok, but when I exported it, the raster looks different (see picture above), how can I solve this problem? I also tried r....
66 views

### NODATA on MapServer

I am trying to generate a DEM mosaic to publish via a WCS using MapServer. Unfortunately I can not remove the NODATA. In MapServer's own tutorials and discussion groups suggest PROCESSING "NODATA = 0",...
251 views

### TIN interpolation problem

I made a TIN interpolation of some height points but the resulting raster appears with some weird lines (like in the pic) What can i do to avoid this result? Here are the input parameters. Sorry ...
114 views

### QGIS Orfeo Toolbox: Smoothing tools generate unwanted black border on a hillshade raster

I'm using the Smoothing (gaussian) and Smoothing (mean) tools in the QGIS Orfeo toolbox to blur a hillshade raster I've generated. However, they both come out with a thick black border at the edge of ...
180 views

### Making DTM from contour vectors in QGIS?

I have been using QGIS (2.18.0) for 6 months and now need to make a DEM from contour vectors. From my reading, I know I have to use GRASS. I am in the process of using this tutorial to achieve that ...
108 views

### Display points with lowest elevation within a 1m2 grid - QGIS 2.18.2

I have a few thousand points measured with totalstation from an archaeological site. The points are measured quite unevenly which makes TIN triangulation and subsequent DEM generation a mess. Some ...
158 views

### “Select a tool” error Saga: Accumulated cost (isotropic)

I'm trying to run Saga's accumulated cost operation in QGIS on a DEM and set of raster destination points, but keep receiving an "Error: select a tool" in the log after a failed run. There are no ...
392 views

### QGIS: How to create a crosstab using SAGA toolbox cross calssification and tabulation?

I am trying to use Cross classification and tabulation SAGA toolbox. I have a raster DEM file (14 classes) and raster file precipitation (13 classes). I want to do cross-tab - but I don't know how ...
83 views

### Blend overlapping DEMs using Open Source / Python

I'd like to blend edges of overlapping DEMs such that the join is a smooth transition (for use with InSAR). Apparently the best interpolation kernel for this, according to the literature, is thin ...
343 views

### Creating a DTM from Contours, via the command line or Python

I am looking to create a gridded DTM/DEM (Digital Terrain/Elevation Model) or TIN (Triangulated Irregular Network) from a set of contours. There are a number of similar questions on both this site ...
2k views

### Creating one DEM from multiple ASC files

I am struggling with this several days and now its time to ask how to do it in QGIS. I have very detailed 27 ASC grid files with overall size of 9 GB created from 1m contours of large area (600 m2). ...
271 views

### Calculate surface elevation from DEM of pit and known volume with which it is being filled

I am using ArcGIS 10.1. I have a DEM of a pit. I have a known volume of material that I want to put in the pit. I want to know what the elevation of the flat surface of this material will be ...
63 views

### Adjacent DEM files have narrow triangular gaps when joined

Newbie here. I've downloaded several DEM files from GeoCommunity which correspond to adjacent regions. When I join them together to form a larger relief map there are triangular 'gaps' on all four ...
1k views

### Is it possible to reverse the trend/values of a raster?

For example - if I have a raster DEM covering a stream with higher elevations in the west (up river) and lower elevations in the east (down river) is it possible to reverse this trend so that the east ...
23 views

### A GeoTIFF heightmap from SRTM embeds vertical planes along lat/lon grids in its 3D representation

I've downloaded an SRTM GeoTIFF from Open Topography and converted it into the grayscale image before I imported it into Blender to improve the quality. It is apparent that vertical planes are cutting ...
44 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 ...
145 views

### Increasing zoom level in 3D View QGIS Desktop?

I would like to increase the zoom level for my mosaic raster image in the 3D View of QGIS Desktop 3.4.4. I made a mosaic out of four raster images downloaded through the STRM-plugin for DEM data. ...
35 views

### Channel network from high resolution DEM for flat areas

I'm working on channel network extraction from a LiDAR DEM (square grid max resolution 0,25 cm), and my area of study is vary flat with some part below the sea level. I applied the classical valley ...
61 views

### Importing several LiDAR (.las) files in GRASS using v.in.lidar?

I'm building a DEM of a terrain in GRASS and have 48 LiDAR (.las) files. I know I can do this by using r.in.lidar (including the list of files as a .txt) and then r.fillnulls However, I want to ...
81 views

### Mapping coastline geometry with SRTM raster?

Working on a map that includes a bathymetry layer, SRTM data for hillshade, and an accurate coastline boundary edge. I noticed though that the pixel resolution of SRTM 90m resolution creates visible ...
50 views

### Improving Sentinel 1 Interferometric DSM Accuracy - Removing Surface Anomalies

I have been working through the ASF's "Recipes" for the creation of a DSM from Sentinel 1 (A and B) imagery. I am able to produce a DSM, and am relatively happy with the results in terms of the ...
51 views

### World DEM speckled outcome solution

I have a world digital elevation model which has been classified into 5 showing the different heights. My issue is that viewing and printing this image as it is results in a speckled look due to the ...
53 views

### Adaptive raster to points sampling based on change of slope in QGIS?

I have a high resolution elevation map and need to convert it to XYZ points. Simple conversion generates a lot of points in flat / constant slope areas which are redundant for 3D terrain generation. ...
89 views

### Viewshed analysis adding polygon mitigation in QGIS?

I am looking at a DSM layer in QGIS and have created a binary viewshed using the viewshed analysis plugin. I want to add a polygon layer with heights to add on top of the dsm layer to indicated ...
197 views

### GDAL merge of DEM data resulting in large black tiles, elevation min/max problem?

I am new to QGIS (former Arc user) and having trouble with the raster merge tool. I am merging 7 tiles of SRTM arc 1 data to cover a province in eastern Ecuador. Data is resulting in large areas of ...
77 views

### Replace values in one DEM with values from another DEM

I have two DEMS. One is a 10m DEM (let's call it DEM-A) covering a large area (projection EPSG 4326). The other is a higher resolution DEM (DEM-B) that was constructed from a structure-from-motion ...
355 views

### Create DEM from either few points or contours without elevation attributes

I have DWG file that contains couple of layers, among others I have "elevations" layer (that consists of only 80 points) and "contours" layer that can be seen on the images below. My goal is to make ...
102 views

### Should I Krige my contour data or use a different interpolation method?

I am using QGIS to calculate the terrain slope, starting from vector contour line data. Using linear interpolation like r.surf.contour gives me a reasonable looking DEM, but is not really useful if I ...
78 views

### Converting Mars Global DTM to Spherical Mesh

I am working on a video game that is attempting to provide a semi-realistic model of Mars. My starting point has been to find and use reliable geographic information to create the "model" of Mars. I ...
271 views

### DSM and buildings height

How can I create a Digital Surface Model in order to collect the height of buildings and what's exactly needed to create a Digital Surface Model? Any software provide creating it (ENVI or PCI ...
107 views

### Mosaic DEM .geotiff in QGIS 2.16

I am attempting to mosaic 2 DEMs from northern Illinois, USA with QGIS. One DEM has a 4m resolution while the other has 2m. Both DEMs have been clipped and converted to .geotiff from larger .adf ...
51 views

### Warning from SAGA when doing Topographic Corrections?

I am trying to use SAGA for topographic corrections for the first time, however I am getting a warning that says: data not in the same grid Can any one suggest ways of formatting the data (DEM and ...
231 views

### Draw raster on top of a Leaflet map

I want to implement a raster layer on top of a Leaflet map that includes the following functionalities: Digital Elevation Model (DEM) terrain height included in each raster cell GPS-Track (I use this ...
286 views

### SAGA GIS Channel network crash

So, i had this very weird bug while treating my dem data lately. I used SAGA to create flows channel networks on a dem i acquired a little while ago. Preprocessed it using sink route detection and ...
46 views

### Does USGS 3DEP data use a hash or checksum?

I'm downloading some USGS 3DEP elevation data, e.g., the file at the following URL: https://www.sciencebase.gov/catalog/item/563afea8e4b0d6133fe7357b The "ID" of this file is given in both the URL ...
101 views

### Weird artefacts/pixels in QGIS-created shaded relief map

I'm working with 30m SRTM data on an terrain map of Cuba. I downloaded the necessary DEM files, merged them and went on to create the shaded relief map in QGIS 2.8 using Raster > Analyze > DEM (...
280 views

### How to calculate best path between 2 points from a DEM in Qgis?

I'm analyzing the roads and paths of a region by calculating how effective the communication is in the region. First I calculated the shortest paths between the points using the actual road map. Now ...
106 views

### Fixing undesirable lines between tiles from SRTM contour line extraction?

I'm trying to make a South American topography map based on SRTM data on QGIS. The problem is a visual one. If the topography contours are extracted from individual SRTM tiles, it results a little ...
201 views

### Identify and calculate area of valleys

I have a shapefile (points) that contains the coordinates of a number of cities in a mountainous area (valleys separated by mountain ridges), and a DEM of the area. I would like to calculate the ...
165 views

### 3D model to DEM, maintain volume?

Bit of a challenge here which I've been grappling with for some time. I'll explain my full work flow so you can reproduce if needed. I'm creating virtual landscapes in Google SketchUp which I ...
54 views

### Combining multiple DEMs into one file geodatabase

I have multiple file geodatabases (approximately 240) each contain a DEM. My issue is taking the DEM from each and putting it into a single file geodatabase without alot of mind numbing work. ...