10
votes
Accepted
Elevation from TIFF file
Save the Excel file as CSV
In GIS, add the CSV file to QGIS using "Layer > Add Layer > Add Delimited Text Layer"
Use "Sample raster values" from "Processing Toolbox (...
- 72.4k
10
votes
Extract raster value at each vertex from line, while keeping the line
You can use "Drape (set Z value from raster)" tool to set the z value of every vertex in the densified line to a value sampled from a raster.
- 72.4k
9
votes
Accepted
Sampling points in raster without generating new file in QGIS
You can use the raster_value function in an expression in the Field Calculator to update a field in your point layer with the pixel value from an underlying raster:
raster_value( 'DEM', 1, $geometry )...
- 19.2k
9
votes
Accepted
Extract raster value at each vertex from line, while keeping the line
Using QGIS expressions, use this expression:
raster_value( 'DEM', 1, start_point($geometry))
This is to get the elevation from the raster called DEM, raster band 1 for the line's start point. To get ...
- 60.2k
6
votes
Accepted
How to calculate area in mountainous regions
For my use, I have this solution:
First I convert my DTM with the tool from SAGA called "Real surface area". After that, I have a raster with the real surface for each pixels, on band 1.
...
- 1,493
5
votes
Accepted
Extract Single (or small number) Contour from DTM data in QGIS
You can use r.contour:
Produces a vector map of specified contours from a raster map.
- 63.6k
5
votes
Accepted
rasterstats zonal_stats - return cell position
You can grab the indices of the mini raster where the pixel value == the statistic value (i.e min or max) using numpy.argwhere, then use the transform/affine to work out the map coordinates.
e.g.
from ...
- 59.8k
4
votes
Accepted
Number of pixels Elevation - Aspect - Slope
A raster has to be rectangular, that is why you get no data values when you clip with a irregular polygon. Maybe slope and aspect cant be calculated at the border to no data. Can you calculate them ...
- 63.6k
4
votes
Accepted
Identifying and replacing specific pixel in DEM using ArcGIS Pro
You can use several ways to locate the offending pixels. If the raster is small enough simply turn it into a point dataset, you can then select the pixels of interest, now represented as a point, by ...
- 41.7k
3
votes
Finding highest point relative to point data
Step 1: Add raster values to points (set z from raster), so your points know how high they are.
Step 2: Run maximum("height field") on your point layer in the field calculator creating a new ...
- 15k
3
votes
Extract Single (or small number) Contour from DTM data in QGIS
QGIS is using this GDAL utility https://gdal.org/programs/gdal_contour.html
and it has an option to create contours not for intervals but for a fixed set of levels
-fl
Name one or more “fixed levels”...
- 60.1k
3
votes
Accepted
Polygons from a raster within an elevation range
Using standard Qgis Contour that is a front end to gdal_contour utility.
The solution to draw polygons instead lines is to add these parameters in addition to the command line, -amin -amax is the ...
- 386
3
votes
How do you interpret a DEM?
A DEM is to my understanding usually created from the interpolation from other data sources, typically point elevations and\or contour lines, the pixel being assigned an elevation value. When I use a ...
- 41.7k
3
votes
Accepted
Using Esri ASCII Grid as DEM + Reprojecting
Following the links you provided I downloaded the data. Opening the text file its clear that even though it ends with a txt file name extension the contents conforms to an ASCII grid interchange file ...
- 41.7k
2
votes
Accepted
How to get the ground level altitude from DSM or Point Cloud using Python
Usually DSM or DEM rasters are georeferenced Tiff files. You can use GDAL or rasterio library to load them into Numpy Array.
import numpy as np
from osgeo import gdal
raster = gdal.Open(&...
- 626
2
votes
Accepted
Calculating area's region in DEM
Use raster calculator to create a binary raster (black&white; 0&1) with this expression: raster_layer_name@1 < 14. Areas below 14 m will appear in white (=1), all areas above in black (=0).
...
- 60.2k
2
votes
Accepted
Convert points with x,y coords and value from to a raster image
You need to use an interpolation tool to convert your points to a surface. Here is a tutorial on interpolation that may help you get started. Here is a link to the interpolation tools available in ...
- 8,817
2
votes
Accepted
Finding average depth of filled sink using ArcGIS Pro
If you want the average of all your sinks then you could convert your difference raster to a point dataset. Each pixel would become a row in your point dataset. Delete out zero difference and ...
- 41.7k
2
votes
Accepted
Feed pixel type of tiles into MosaicToNewRaster()
There's an ArcGIS Idea about this:
arcpy.Describe.PixelType returns useless value
From the help you can get the pixel types output by getPixelType and required by MosaicToNewRaster:
You can use ...
- 59.8k
2
votes
Determining slope percentage using ArcMap
Slope angle is equal to Atan(slope ratio)*180/Pi
For a slope ratio of 15/100, the angle in degrees is 8.53
You don't need to convert all the slopes values from your raster in degrees, just use this 8....
- 3,012
1
vote
DEM 3D problem in QGIS
qgis3threejs treats the canvas outside the DEM as having elevation 0. If your DEM is well above sea-level, you get the effect you're seeing. Look at this issue on the qgis2threejs repository for hints ...
- 5,871
1
vote
Accepted
Creating DTM from COPC LAZ Files using PDAL
So the batch was the problem. With a little tweaking it has worked.
The solution is.....
@echo=off
for %%f in ("*copc.laz") do ( pdal pipeline "raster_pipeline.json" --readers....
1
vote
Accepted
Elevation dataset appears to have come with all of the Eastings wrong
From the metadata - the CRS is NAD_1983_10TM_AEP_Forest (EPSG:3400)
When brought into QGIS in this CRS, the data displays correctly:
- 59.8k
1
vote
Accepted
Correspondence of 0m elevation height of a digital elevation model (Copernicus DEM) to mean sea level
Here is the answer given by the Support team of Copernicus:
The definition of the 0 m elevation for ocean areas is not dependent on the acquisition date of the input images. Please note that the ...
- 151
1
vote
Ortho-rectifying standard non-rectified Maxar satellite imagery
You can definitely use your existing imagery to georeference the image to your existing imagery to help align the two data. See here for help on georeferencing in QGIS. There are also numerous ...
- 8,817
1
vote
Accepted
Fixing errors in old DTM in QGIS
A couple of options:
1 - r.mapcalc
r.mapcalc "output_with_nodata = if(input_dem<=0.01, null(), input_dem)"
2 - Save as + "no data" range
right-click on the layer name, Export -&...
- 6,309
1
vote
Elevation data from WMS or WMTS?
If your only goal is to create a terrain profile, maybe the geoservices REST service could be helpful here:
https://geoservices.ign.fr/documentation/services/api-et-services-ogc/calcul-altimetrique-...
- 4,661
1
vote
Accepted
Adjusting flow direction of river based on DEM in QGIS
Solution 1
Use select by expression with this expression where DEM is the name of your raster layer (digital elevation model):
raster_value ('DEM', 1, start_point ($geometry)) <
raster_value ('DEM'...
- 60.2k
1
vote
Accepted
Float32 to UInt16 terracing problem
Providing the scale parameters as in my third code example works. I was expecting the gdal_translate to preserve units but change potential precision. It doesn't. The scale can be assigned to ...
- 43
1
vote
Getting high resolution DEM for a location
Use https://apps.nationalmap.gov/lidar-explorer/#/
The darker the green the higher the accuracy
DEM is available by using the tools (ctrl create window)
1m DEM or 10m is available depending on your ...
- 49.3k
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