49
votes
Accepted
Creating transparent hillshade?
Nutshell
Each set of 3 images below should be read such as "grey (band) + opacity (band) = transparent result". You can test these processes within minutes via the associated github hosted ...
- 2,633
22
votes
Splitting raster into smaller chunks using GDAL?
There's a bundled python script specifically for retiling rasters, gdal_retile:
gdal_retile.py [-v] [-co NAME=VALUE]* [-of out_format] [-ps pixelWidth pixelHeight]
[-overlap ...
- 4,718
22
votes
Accepted
What is NASADEM and when it will be released?
NASADEM is a full reprocessing of the SRTM data using state-of-the-art interferometric processing techniques. It also improves accuracy, reduce gaps and improve the quality of the data used to fill ...
- 1,209
20
votes
Choosing DEM in France?
The answer is not as simple as the question may imply. If we had one "best one" we would not need the others, we would just use the best. Horses for courses though, needs matter.
Saying that.
This ...
20
votes
Accepted
Hillshade results look too grainy
I think you are using Geographic CRS not Projected CRS. Usually this hillshade output is due to you are not using a projected DEM such as UTM projection with a meter unit. You need first to reproject ...
- 39.6k
17
votes
17
votes
Producing smooth and consistent contour lines from SRTM
To smooth your contours it is the best way to smooth your DEM first.
Here are some useful information: What raster smoothing/generalization tools are available?
I'm using SAGA GIS for this task.
...
- 4,344
16
votes
Accepted
calling gdal_merge into python script
Add an empty argument in the first approach (because gdal_merge.py parses arguments starting from 1 and not 0):
import sys
sys.path.append('C:\\OSGeo4W64\\bin')
import gdal_merge as gm
gm.main(['', '-...
- 14.1k
14
votes
Accepted
Converting LAS 1.4 to 1.2
For converting to las 1.2 from las 1.4, PDAL's translate command is an option:
pdal translate --writers.las.minor_version=2 input-las14.las output-las12.las
LAStools can also do the job:
las2las -i ...
- 936
13
votes
Hillshade shows grid texture artifacts
The problem is because the DTM has a high-resolution pixel size when data (in my opinion) doesn't have the same resolution is some areas.
For example, direct hillshade raster:
Check pixel values (...
- 13k
12
votes
Smoothing DEM using GRASS?
Tom Patterson, the lead cartographer at the U.S. National Parks Service has some excellent tutorials on working with DEM data to make beautiful shaded reliefs. Part of his workflow involves using ...
- 1,775
12
votes
How to perform a slope analysis in QGIS?
Slope analysis is performed on a DEM (raster layer with elevation values). This is one way to do it. If your contours have an elevation value, you can use the interpolation option (raster/...
- 2,972
12
votes
Accepted
Querying Elevation Data in Postgis
Your elevation points are definitely regularly aligned and hence there is no need to bother about nearest neighbors. The value of the pixel in which your point fall into is always the value of the ...
- 2,520
12
votes
Accepted
Making an animation of an evolving digital elevation model
Probably the best tool for this is Paraview. Once you've downloaded and acquired that you'll want to load your images:
Use the CSV reader to load them:
Below, you can find filters faster by pressing ...
- 1,811
12
votes
Accepted
Update DEM based on line feature in QGIS
You can use r.carve within QGIS and set up a negative stream depth to increase the height of your DEM along your line feature
(In the image below a positive stream depth have been applied to the DTM)
- 2,012
11
votes
Accepted
How to create composite hillshade?
The linked source mention "change its fusion mode to < Multiply >", so the operation to do is not a simple average of input hillshades (for this, see also How to average gdal_hillshades?). It's ...
- 2,633
11
votes
In hydrologic terrain analysis is there a difference between "pits", "depressions", and "sinks"?
There is a difference, and I recommend the typology presented by Lindsay (2015) be used.
Lindsay (2015) presents a typology which defines a pit as a single cell in a DEM whose elevation is below that ...
- 1,811
11
votes
How to replace pixel values in a single band DEM?
You can do something similar using gdal_calc.py, e.g.:
gdal_calc.py -A dtm.tif --calc='((A>=100)*(A<=200))*A+((A<100)*0)+((A>200)*0)' --outfile=dtm_reclass.tif --NoDataValue=-32767
This ...
- 4,862
11
votes
Accepted
Generating STL (3D) file from raster ASTER GDEM data?
I know QGIS has a plugin that export DEM to STL using DEMto3D, and I tested on a DEM and it worked. The description of the plugin mentioned that clearly:
DEMto3D is the first tool that links GIS (...
- 39.6k
11
votes
Accepted
Merging drone/photogrammetry-derived DEM and satellite-derived DEM using ArcGIS Pro
Assuming:
both are in the same projection / coordinate reference system,
you have a Image/Spatial Analyst license, and
NoData has been set correctly on the High res DEM.
You could use a Raster ...
- 60.2k
10
votes
Understanding min and max values with Mosaic to New Raster?
As whuber mentioned, often statistics found in the raster properties are sometimes approximate or are out-of-date. They are predetermined properties that can be misleading to the actual raster values.
...
- 41.3k
10
votes
Accepted
Getting incorrect slope values from an ASTER DEM in QGIS?
Aster DEMs are in EPSG 4326 (lat lon WGS84). According to the GDAL DEM documentation:
For LatLong projections near the equator, where units of latitude and units of
longitude are similar, ...
- 2,972
10
votes
Extracting Values to Points without ArcGIS Spatial Analyst?
Script:
import arcpy, traceback, sys, os
pntFile=arcpy.GetParameterAsText(0)
rasters=arcpy.GetParameterAsText(1)
rasters=rasters.split(';')
theFields=[x.name.lower() for x in arcpy.ListFields(...
- 22.4k
10
votes
Different DEM range values in QGIS and ArcGIS
In both software, the initial data range is just an estimate, which can easily be manipulated. For instance, should you display several DEM side by side, you will likely want to use a common range so ...
- 38.4k
10
votes
Accepted
Adjacent DEM color matching in QGIS?
In the main menu bar, go to Raster | Miscellaneous | Build Virtual Raster and select all the tiles you want to group (don't forget to uncheck the Place each input file into a separate band tickbox). ...
- 3,048
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 (...
- 72.5k
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.
- 72.5k
10
votes
Make the pixel values of the DEM correspond to the actual heights
I had a similar SE-GIS question several years ago. The answer: by default, QGIS displays an estimate of the min/max values, which results in the unexpected values. To see this, open up the Min/Max ...
- 7,759
9
votes
Seeking tool to generate Mesh from DTM?
We have just created an open source project that will help you do exactly what you want. Tin-Terrain is a simple command line tool that will generate a mesh from DEM files either as TIN or TRN.
The ...
- 245
9
votes
Creating transparent hillshade?
Another way to get the same result of a non-grey canvas more suitable for combining with other layers is the 'combined' option in gdaldem.
It performs a slope and hill shade and combines the two in ...
- 606
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