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 ...
17
votes
Gdal: how to get the max and min altitudes of my topographic raster?
With Python, you can access raster statistics using the Python GDAL/OGR API.
from osgeo import gdal
# open raster and choose band to find min, max
raster = r'C:\path\to\your\geotiff.tif'
gtif = gdal....
- 51.3k
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
15
votes
Accepted
Remove border lines of SRTM tiles rendered as hillshade
SRTM tiles (3601 px * 3601 px in this case) have 1-pixel overlaps in between. When you apply transparency (or reduced opacity) to your hillshade layer, such overlapping pixels stand out. You may have ...
- 30.1k
9
votes
Accepted
Extracting flat areas and saving them as lakes using QGIS?
You need to extract the slope first from the DEM using the Raster -> Terrain Analysis -> Slope OR Raster -> Analysis -> DEM (Terrain Models). Then use the slope raster to extract the lakes ...
- 39.6k
9
votes
Accepted
Blocky SRTM hillshade in QGIS
Your screenshot depicts the classic blocky "herringbone" pattern resulting from applying a Nearest Neighbor resampling to raster elevation data. The solution is to instead apply either a ...
- 7,759
8
votes
Download new SRTM 30 meters
I answered a similar question here
You can download and clip a portion of the SRTM 30m DEM with one
command with the
elevation
Python command line tool.
Install it and perform the self ...
- 271
8
votes
Accepted
Why do "stripes" appear on raster?
The resampling method 'near' or 'nearest' is generally to be considered only for succinct/classified data, it attempts to assign a cell value based on the closest source pixel:
This is most commonly ...
- 25.6k
7
votes
Accepted
Which is better for measuring actual ground elevation, NED or SRTM?
This is by no means an answer to your specific problem but an explanation of elevation data and vertical accuracy. Also, this all wouldn't fit in a comment.
Only a select number (depending of area ...
- 5,757
7
votes
Downloading SRTM data
You can download and clip a portion of the SRTM 30m DEM with one command with the elevation Python command line tool.
Install it and perform the self check with:
$ pip install elevation
Check if ...
- 271
7
votes
Getting correct elevation values from Digital Elevation Models
It's impossible to pinpoint what is going on without looking at the data per se, but a wild guess would be due to the DEM being a DSM and not a DTM. I don't know how well you know these terms, but on ...
- 3,101
6
votes
Accepted
Does a SRTM DEM image show details such as fields?
Chris,
Your confusion stems from the distinction between the image represented by image 1 (a true color image) and the DEM you downloaded. The two are very different things and this distinction is ...
- 826
6
votes
Accepted
Use "SRTM Downloader Plugin" with "QGIS 3.4"
I have tested the plugin and it is working fine in my machine.
One common way to download (SRTM among other) data is searching it in Earth Explorer site.
All the information about how to use the ...
- 13.3k
5
votes
Accepted
SAGA tool 'Relative Heights and Slope Positions' - What do results tell me?
Now, the answer from the developers of the tool, who kindly allowed me to forward the answer here. I translate and do my best to reproduce what I learnt from Dr. Conrad:
The only expected input-...
- 141
5
votes
Does a SRTM DEM image show details such as fields?
In the text there is basically an error in that there should be another sub heading between the SRTM data download section and the imagery download section. We provide a methodology for obtaining SRTM ...
- 51
5
votes
Choosing DEM in France?
As "@user two seven two three nine" says, it depends on what you are trying to do.
For the geosciences, there are a number of relevant papers in "Elevation Models for Geoscience", Geological Society ...
- 1,284
5
votes
Least Cost Path Analysis in QGIS?
It seems you're mostly confused about how to define cost. I highly recommend this post by Amanda Briney on GIS Lounge, especially the Requirements for Least Cost Path Analysis section.
Cost can be ...
- 24.1k
5
votes
Accepted
How to compress DEM SRTM files?
You most probably do not want to compress DEM data with JPEG, that would be lossy and introduce weird steps in the data.
Instead I recommend the DEFLATE compression. To improve the size savings you ...
- 10.4k
5
votes
Accepted
Creating color physical map using SRTM V2 GeoTIFF tiles in QGIS
The area around the Caspian Sea is below sea (ocean) level. Baku, capital of Azerbaijan, is 28m below sea level.
So using one single color ramp applied to a Digital Elevation Model that represents ...
- 61.1k
4
votes
SRTM vs Google Earth Pro elevation data
Both are the same.
Google Earth uses the SRTM elevation data according to this topic on the Google Earth Help Forum:
The global terrain dataset is 90M SRTM
It says the same thing on Wikipedia:
...
- 983
4
votes
Accepted
Looking for good quality DEMs for Svalbard and Faroe Islands
The amazing ArcticDEM project has 2m and 5m coverage for much of the arctic, some of it available as time series. Not all of the data has been processed yet, but it looks like they have coverage of ...
- 12.8k
4
votes
Remove border lines of SRTM tiles rendered as hillshade
As described by @Kazuhito, the tiles should be combined into a virtual raster. Their method is performed within QGIS. If you have a large number of tiles you may prefer to do this from the ...
- 748
4
votes
QGIS raster merge results in a black rectangle
The merge was not successful:
towards the end of you log you can read:
MemoryError
I would assume (also looking at the shape of the output "map", and judging from the large amount of time it took) ...
- 6,314
4
votes
gdal translate resampling -r flag has no effect?
Resampling applies when the gridding of the input file is different from the gridding in the new space (most of the time, a warped space due to reprojection). It also makes sense when the size of the ...
- 49.3k
4
votes
Accepted
QGIS "Profile Tool" Plugin inaccurate reading
The SRTM DEM has a ground resolution of 30 meters (1 arc-second), see https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission#Highest_Resolution_Global_Release and references.
So the elevation ...
- 4,598
3
votes
Gdal: how to get the max and min altitudes of my topographic raster?
Using gdalinfo and jq you can get what you need in a succinct fashion. This assumes that band that has your min/max is the first one (change the index if not).
gdalinfo -json -mm input.tif | jq ....
- 69
3
votes
Accepted
gdal and google earth (and my gps) not reporting the same value
From MIL-PRF-89020B (which includes SRTM requirements), Section 3.3.1.1.2, DTED1 absolute vertical accuracy is 30m (90% Linear Error, to MSL). DTED2 absolute vertical accuracy is 18m (Section 3.3.2.1....
- 12.7k
3
votes
Accepted
Finding the lat/long bounds of a 1km square (for all of Europe)
You need to convert your lat-long bounding box into a bounding box in a projected coordinate system in metres. You then chop this up into 1,000 unit boxes, giving you kilometre squares.
There are pan-...
- 59.4k
3
votes
Selecting DEM that best determines shore line using ArcGIS Desktop?
I tried replicating this using Spatial Analyst. Firstly, I created three lines in different feature classes (though they could be in the same feature class).
Topo Line (blue)
DEM 1 (red)
DEM 2 (...
- 21.7k
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