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Questions tagged [dem]

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

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16 views

Calculate average slope values for a point using 50ft vector perpendicular to contour

I am trying to calculate the average percent slope of a hillside on either site of a data point. I tried extracting info from a DEM using a radius around the point, but I believe a more accurate ...
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29 views

Creating DEM in GRASS?

I need to create DSM and DEM with resolution 0.4 m. I tried to create DSM with resolution of 1m, everything was ok, but when I set higher resolution, then raster have a stripes with No Data values. ...
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1answer
98 views

Merging 1m DEM to 30m DEM?

I have a base 30 m.Dem . However, i also have 1m Dem for an area of interest only. I would like to overlay the 1m Dem on the 30 m Dem meaning the area of interest will have 1m and the rest 30m. Is ...
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42 views

Creating Left and Right Image pair to view with 3D goggles in stereo from DEM or Hillshade?

How does one create the stereo pair for viewing in a program such as StereoPhoto Maker? I have processed lidar that I'd like to turn into hillshades and then view in this kind of software, with 3D ...
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1answer
114 views

Line of Sight Analysis using Points and DEM

I have a DEM and a point feature class with the elevation value from the DEM as an attribute plus with x number of feet added to it representing a tower location. I would like to do a line of sight ...
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1answer
143 views

Resampling 0.7 m LiDAR (in raster already) to 10 m DEM in R?

How do I resample the 0.7 m LiDAR to 10 m DEM in R? What are the basic rules for checking the consistency?
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40 views

How to retrieve GIS data in Multiple Orthophoto at point level

I have been using a python script that can read Data from Orthophoto(*.tiff) of size 300Mb-2Gb. But this is taking 32s per request of lat-long, which is not ok. I have different Orthophotos with ...
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0answers
113 views

ALOS/PALSAR High Q DEM 12.5 Accuracy

Does anyone know the XYZ accuracy for the Phased Array L-band Synthetic Aperture Radar (PALSAR) DEMs (12.5 x 12.5 px)? Is there a document for reference?
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25 views

AW3D30: DSM file is grayscale 32 bits?

I downloaded multiple areas in AW3D30, but each time, the DSM file is 32 bit (instead of 16 as indicated in the specs), and the 32 bits are grayscale with the alpha channel always to 255. (I'll be ...
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41 views

How can I change the elevation of a lake on a DEM so I show the lake bottom contours?

I'm studying the drainage of a lake and I have a DEM of the lake and the surrounding area. I already identified the shorelines of ancient lake levels at higher elevations, but I would like to keep ...
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43 views

Erroneous contour polygons in QGIS 3

I have a global DEM and try to calculate contour polygons for 4 different heights in QGIS. In the first image below, you can see the colored DEM (white = lowest; yellow = higher; orange = highest) as ...
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1answer
323 views

Reclassify and combine rasters in QGIS?

I have a vector layer containing watercourse location which I have rasterized. I also have a DEM containing elevation data for the region in which the watercourses are located. I would like to ...
5
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1answer
279 views

QGIS: Edit elevation in DTM to get correct slope of a river

I am new to QGIS and just need it to do a hydrolocic analysis of an area of which I later make a flow model with HEC-RAS 2D. I made it according to this tutorial: https://www.youtube.com/watch?v=Ro-...
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2answers
106 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 ...
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44 views

Smoothing/denoising DEM to prep for 3D printing?

My DEM was generated from contour lines (as well as break lines and point height data), and the contours persist in the DEM despite doing some basic denoising (although i may not have used the optimal ...
8
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1answer
135 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 ...
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3answers
266 views

DEM of difference - estimate the error - simple method

I have two DEMs of the same area, measured at two different dates. Subtracting one from the other, I can create a DEM of difference (DoD) to find out about the volumetric change in m³. DEM 1 has a ...
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0answers
39 views

White grid appears when reprojecting DEM in ArcGIS Desktop?

I am using ArcGIS Desktop 10.5. I have a DEM .tif archive, in WGS 84. The specifics are: Then, I try to reproject it to WGS 84 UTM 19S. Project and transformations -> Raster-> Project Raster I use ...
2
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1answer
107 views

How to Calculate area of LULC at different elevation by using zonal statistics as table tool [closed]

I have to calculate the area of different land classes like forest,barren land etc from my classified land use data at different elevation zones at an interval of 100m. I have DEM of my study area ...
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1answer
164 views

Creating DEM from mesh? [duplicate]

I have a mesh ( with points and triangles that define it), and I will need to create a DEM model out of it ( in geotiff format if possible for space consideration, if not, then in ASCII grid format). ...
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2answers
76 views

How do I combine these two rasters?

I have a raster representing rivers/drainage basins within a terrain: I have a raster DEM of the terrain: In the basin raster, everything in black is 9999. White is nodata. The DEM is obviously a ...
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1answer
69 views

How can I use line vectors to alter my DEM?

I'm trying to use vector lines to change the height of the areas of my DEM that they overlay. They trace rivers, and i'm hoping to assign arbitrarily high values to the rivers so that my least-cost ...
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1answer
611 views

How do I create a binary mask using Pixel values from a Numpy Array over a certain value (i.e. >1000), in Python [closed]

I would like to create a binary mask using the height values from a Digital Elevation Model, and export this out as a tif. For example, generate a mask for areas over 50m My code so far: from osgeo ...
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0answers
86 views

DEM - calculate shortest/easiest path over mountain range [duplicate]

In QGIS, I have a mountain range with a valley on either side (DEM raster file). Is there software or a plugin that allows me to calculate the easiest pathway over the mountain? The answers at Cost ...
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2answers
147 views

Getting grid points for DEM purpose that is bounded by surveyor points?

I have a list of surveyor points, and I will need to create a DEM model out of it ( in geotiff format if possible for space consideration, if not, then in ASCII grid format). I need the DEM for ...
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1answer
62 views

Reclassify with attribute

So, I don't really know how to word what I want to ask, but I took a DEM file and did used the raster calculator to select a certain elevation range. After that I reclassified it to separate it into ...
1
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1answer
94 views

Converting RTK Elevation Data to DEM?

I have a shapefile that contains elevation data. I want to eventually convert this to a slope layer. I'm assuming I have to convert to a raster, then a DEM, then slope. Is that correct? If so, ...
3
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1answer
87 views

Interpreting cell coordinates from DEM?

I'm using Environment Agency DTM LiDAR data which I import into Mathematica in ASCII format to produce ground surface models, sections, etc. The process works fine, but I'm unclear whether the cell ...
4
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1answer
81 views

Using NAVD88 geoid in Northern Canada?

The USGS NED (1-arcsec) dataset is available for the continental US as well as most of Canada. It is based on the NAVD88 vertical datum. I am interested in using the DEM to orthorectify SAR scenes in ...
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1answer
90 views

Image not draping over DEM in ArcScene?

I saw Images not draping onto DEM in ArcScene? but it is different from my issue. I have an image with projection: NAD_1983_StatePlane_Oregon_North_FIPS_3601_Feet. I have a DEM and set the base ...
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1answer
142 views

Extracting certain area from DEM using ArcGIS Desktop?

Using ArcGIS Desktop, how do I extract a certain area (uniform 1 km from the entire coastline) from a particular year's DEM image?
2
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1answer
202 views

Error in orthorectification of Radarsat-2 scenes with GDAL and RPC + DEM information

I am trying to use a DEM rational polynomial coefficient (RPC) information to orthorectify radarsat-2 images with GDAL 2.2.1. I have successfully done this with Orbview-3 images using the tutorial ...
2
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1answer
861 views

Why ground model from point cloud in Global Mapper is inaccurate?

I have a LAS file that I assumed was based on LiDAR, but it is actually based on ADS (airborne digital sensor) imagery, according to the body that captured the data. I load the file in to Global ...
2
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2answers
216 views

Seeking for a solution to convert GeoTIFF to 3d WKT

I am trying to convert some DEM in .tif image to polygon geometries representing 3 dimensional triangles that is Well-known text (WKT) - 3D (x, y, z) I was able to use SAGA to convert my GeoTIFF ...
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1answer
52 views

DEM to bmp for cnc carving query

I'm importing grayscale elevation images (bmp and jpeg) into a program I use for 3d CNC terrain carving. I've been downloading Hi-Res terrain corrected DEM files from ALOS PALSAR. I bring them into ER ...
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1answer
160 views

Combing multiple LAS files with different vertical and horizontal accuracy?

The data set in question was made using .las and .zlas files from respectable sources. Data set 1 was collected in the Fall of 2014. The RAW flight line swath data was processed to create classified ...
0
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1answer
102 views

EU DEM in GRS80 EVRS2000 with geoid EGG08 --> Make it comparable to Black Sea 1975 for Romania

I got contour lines for western Romania in vertical system Black Sea 1975 which is based on elevation data with 100 m resolution. Now I would like to compare that to the EU DEM with higher resolution. ...
4
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1answer
55 views

Seeking algorithms for DEM generation? [closed]

What are the different algorithms employed for the generation of a Digital elevation model from images captured using an unmanned aerial vehicle ?
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2answers
146 views

Determining flood extents based on a daily flow? [closed]

I have a DEM raster and daily average flows (e.g., 50Ml/day). And I want to determine how far the water extent goes when the flow accumulates for 7 days based on 50 ml per day?
4
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1answer
187 views

Hack's law for river basins

The hacks law relates the longest stream length with the catchment area of the basin. How can one construct a hack's distribution for a basin and upto what scale the sub basins have to be taken as ...
0
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1answer
43 views

Error in change of projection from Lat/Long to UTM

Why does the the DEM when converted to UTM Zone 43N system give all values as 0 in QGIS? I followed the standard procedure of saving the parent layer and then assigning the CRS. When I open the same ...
2
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1answer
67 views

Working with NaN values in channel network in QGIS?

I have downloaded the conditioned 15s HYDROSHEDS dem of asia and after clipping the desired extent proceeded to evaluate the catchment area. However the next step of channel extraction renders NaN ...
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1answer
923 views

Converting GeoTIFF to USGS DEM or DTED using GDAL

I have been looking the documentation for gdal_translate and it doesn't list the -of format available options there. So I tried looking at the source and basically ended up read the SetFromUserInput ...
2
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0answers
76 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 ...
2
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1answer
138 views

Extracting Road Terrain Properties using DEM / LIDAR

I want to extract following road terrain data from DEM but I'm not sure if its possible. Can i extract these attributes using LIDAR if not DEM ? These are the data fields I need: Horizontal curve ...
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1answer
175 views

SRTM/DEM 1m resolution (batymetri) to point [closed]

I have bathymetry data (1 huge data) = SRTM/DEM/FGDBRaster (0,9818m resolution pixel, floating, 32 bit, 45 GB size) and an alternative data (split into small pieces data) = same data but with 1m ...
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1answer
67 views

Origin of LandViewer DEMs?

does anyone know how DEMs that can be downloaded from LandViewer are generated? They have higher resolution than SRTM and other free sources.
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1answer
267 views

Determining elevation of a point from a DEM in QGIS?

I have created a series of DEMs that layercake on top of each other. I would like to be able to lookup a coordinate and get the elevation that has already been interpolated. The goal is to ...
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5answers
298 views

Have DEM, need polygon outlining region above a certain elevation

I have a DEM in HGT format. I need to isolate all areas above a certain elevation and view them as polygons. Something like this (let's say the pink polygon is everything above 1000m): Seems like ...
1
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1answer
41 views

'Regular Points' vector layer in Bonn

I've downloaded the bonn version of QGIS. Using the 'regular points' vector analysis tool, I've set some 5m regular points over a field so that I can use the x,y coordinates to plot them and measure ...