39
votes
Choosing colour-ramp to use for elevation?
First off, let me say how much I appreciate this question. I have seen so many example of inappropriate colour palettes applied to digital elevation models that it's good to see that people are ...
- 10.8k
24
votes
Accepted
Interrupting contour lines beneath elevation labels (instead of using label buffers) using QGIS?
Yes, doable. Normally I'd suggest a partially transparent buffer, but I see why you want to do this cartographically.
This could be slow, and you need to manually decide where you want the labels to ...
- 19.8k
23
votes
Accepted
How is elevation and altitude measured?
Altimeters use barometric pressure to measure altitude or elevation. Your watch likely uses a Baro-Altimeter. The problem with that is that the barometric pressure also changes with the weather. As ...
- 446
21
votes
Accepted
Meaning of "Elevation above surface of ellipsoid"?
The elevation above the ellipsoid (ellipsoidal height) is the elevation above a mathematical model that approximates the shape of the earth. The current most common one is WGS84. These are the ...
- 3,041
13
votes
Seeking alternative to Google Maps Elevation API
I've been working on opentopodata.org as a free, open alternative to the Google Maps Elevation API.
Request URLs look like this:
https://api.opentopodata.org/v1/eudem25m?locations=51.875127,-3....
- 309
12
votes
Accepted
Obtaining elevation data for points using QGIS
Basic steps to get elevation data in GPS points:
Obtain an elevation raster for your area of interest. You'll need a DEM (Digital Elevation Model) raster, which is a raster of pure elevation data ...
- 23k
11
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 ...
- 2,402
10
votes
Seeking free elevation data for Europe?
Since 2013 there is the EU-DEM 25 m: new Digital Surface Model (DSM), representing the first surface as illuminated by the sensors. You can download the GeoTIFF files here: http://www.eea.europa.eu/...
10
votes
What resampling technique should be used to reproject an altitude raster?
Michael Miles-Stimson is correct in his comment above; nearest-neighbour (NN) and majority resampling methods should only be applied to categorical data, i.e. nominal and ordinal level data. Elevation,...
- 10.8k
10
votes
Accepted
Converting sign for a 32-bit GeoTIFF with an open source tool?
I don't know if this is the easiest way, but one way would be to use gdal_calc.py from GDAL:
gdal_calc.py -A positive_values.tif --outfile=negative_values.tif --calc="A*(-1.0)"
- 2,232
9
votes
Choosing colour-ramp to use for elevation?
In addition to what has been mentioned there are a few more things to consider. You can enhance the 3-dimensional impression of the map by not only varying the color hue but also the saturation, ...
- 1,579
8
votes
Seeking free elevation data for Europe?
In 2016, the Japan Aerospace Exploration Agency (JAXA) released a new free 30 m (1 arcsec) resolution global topographic data set called ALOS Global Digital Surface Model "ALOS World 3D - 30m" (AW3D30)...
8
votes
Accepted
Why not measure elevation from the center of the earth?
One thing to keep in mind is that lat/long is geodetic and not geocentric:
If we were to calculate elevation as a radius from the center of the ellipse, our elevation lat/long would be different ...
- 5,313
8
votes
Reducing elevation from DEM using ArcGIS for Desktop?
Building on Michael's excellent answer, I would recommend using the Con (Spatial Analyst) tool to take a "slice" out of your DEM. The first screenshot shows the parameters you would likely want to ...
- 50.2k
8
votes
Accepted
Subtracting out slope (in general) of DEM using ArcGIS for Desktop?
Subtract the trend surface from the DEM.
Linear trend (1st order polynomial)
2nd order polynomial trend
Per @radouxju's comment - the trend line can be shifted down to avoid negative values by ...
- 51.7k
8
votes
Accepted
How to find all points with certain elevation difference between them in QGIS
The easiest way is to import your points into a format that can be queried with SQL, like PostGIS, SQLite or Shapefile (using OGR).
Then you can query:
SELECT *
FROM [table] a, [table] b
WHERE a.[...
- 3,041
8
votes
Accepted
Determining if shapefile has elevation or z coordinate values stored using ArcGIS Desktop?
Your question title and content are a little ambiguous as to what you are asking. As for checking to see if a shapefile has z information, which seems to be your ultimate question, is as follows:
...
- 5,727
8
votes
Accepted
QGIS - Lakes - Change Polygon Z values, using Single Field Value
In QGIS 3.0, run the "set z value" algorithm. Hit the button next to z value and select the field containing your desired z values.
- 26.2k
7
votes
Extracting elevation from .HGT file?
GDAL can read/write these raster formats with the SRTMHGT driver. This means you can view the raster with QGIS, ArcGIS, or use GDAL utilities like gdallocationinfo to get values from a point, e.g.:
...
- 39.7k
7
votes
How is elevation and altitude measured?
0 altitude in Bangladesh is likely not exactly the same then 0 altitude in Sweden even when you define both being equivalent to the sea level. This is because sea level is not the same every where. It ...
- 1,579
7
votes
Interrupting contour lines beneath elevation labels (instead of using label buffers) using QGIS?
During my research to achieve a mostly dynamic labeling of contour lines in QGIS 3.10, I put everything together in a small cooking recipe and changed my original answer to share the findings with the ...
- 3,623
7
votes
Extract elevation data from Landsat / MODIS imagery?
Landsat and Modis are optical sensors, which means that they provide digital numbers of reflected materials that are within the electromagnetic spectrum. These values correspond to the wave length of ...
- 9,203
7
votes
How to create contour lines from point data using QGIS?
Using the Contour plugin. Generate isolines and/or filled contours a set of data points.
- 319
7
votes
Identifying south facing mountain land, above an elevation, within a slope range, less than fixed distance from major roadways
The following is a rough outline of what you might do. I won't include a great deal of detail, you can research further using these terms and/or ask new more specific questions.
Note: you will need ...
- 51.7k
7
votes
Accepted
Find lakes on an elevation raster
In your comments above you expressed interest in my suggested method, and so I am providing a more detailed answer here. The method uses the tools available in Whitebox GAT, the open-source GIS that I ...
- 10.8k
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 ...
- 5,727
7
votes
Accepted
Getting elevation at particular coordinate (lat/lon) programmatically (but offline)?
You can use the rasterio library:
import rasterio
coords = ((147.363,-36.419), (147.361,-36.430))
elevation = 'srtm_66_20.tif'
with rasterio.open(elevation) as src:
vals = src.sample(coords)
...
- 51.7k
7
votes
Accepted
Inaccurate altitude GPS data with my Android?
There could be a number of problems in play here depending on where you are, what the terrain is like, and what the capabilities of your device are?
If your device uses pressure sensors they may not ...
- 3,412
7
votes
Creating Buffer Polygon following Elevations using ArcGIS Desktop?
Workaround for what you describe in absence of spatial analyst:
arcpy.Buffer_analysis("target","../buffer.shp", "100 Meters")
arcpy.FeatureVerticesToPoints_management("buffer","../points.shp","ALL")
...
- 21.4k
7
votes
QGIS: Edit elevation in DTM to get correct slope of a river
Create a new shapefile having the same CRS as your DEM. Create a numeric field (Whole number or Decimal number), like heightadd, and Add to Fields List.
Draw a polygon on the area you want to add ...
- 24.5k
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