Hot answers tagged srtm
9
Update:
I think wget would be better, i just don't use it very often:
wget -r -A.zip http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/
Also see for some retrieval wait options (if you want to be courteous):
http://superuser.com/questions/178297/wget-terminates-unexpectedly/178326#178326
You could curl the files with a little bit of text editor work.
For ...
9
For a local solution, GRASS can be scripted to do this:
# extract raster values at our points
# use cubic convolution for interpolation between DEM locations
v.drape in=my_pts out=pts_srtm_elev type=point rast=srtm_dem method=cubic
I ran an extended version of this for one of my use cases and performance of v.drape was no issue at all.
6
Download the source code from here
http://www.osola.org.uk/elevations/index.htm
SRTMGeoTIFFReader.php is the clever file the reads the GeoTiff and converts the elevation values (in meters) into Lat/Lng coordinates.
I doubt this is exactly what you want but it does give you a solid base on understanding the process required to accomplish the task from your ...
6
Mike Migurski (of Stamen Design) recently made a major new open terrain map: details on his blog and I put up a quick map viewer for it. It does terrain relief shading with various DEM sources combined with roads, labels, etc from OpenStreetMap. The source code to generate the map is on GitHub.
6
TopOSM has terrain tiles - though limited coverage (US Only)
http://www.toposm.com/us/
Full Details
http://wiki.openstreetmap.org/wiki/TopOSM
All the Rendering and Source files are available
http://svn.openstreetmap.org/applications/rendering/toposm/
License is the same as Open Street Map
OpenStreetMap Data is available under the Creative Commons ...
5
You can generate your own using Maperitive:
generate-relief-igor command
generate-tiles command
A sample hiking map using such tiles.
4
http://dds.cr.usgs.gov/srtm/version2_1/Documentation/Continent_def.gif
You can use http://www.latlontoelevation.com/ lat/lng to get the Shuttle Radar Topography Mission (SRTM) data too.
4
SRTM data is easy to download for a given area, I've use this site in the past. The files aren't huge, and you can get them as georeferenced TIFFs. Downloading the whole world might take a while, but a couple of tiles covers a pretty large area. The issue you might have is with horizontal resolution, which is about 90 metres for most of the world, and the ...
4
The interpolation modules in GRASS can work with a line vector, such as contour lines, to create a DEM raster. So you could create a DEM raster from your contour lines, then "correct" the ASTER GDEM with this data. The catch will be in matching elevations from the contour-based raster to the ASTER GDEM, to avoid a terrace effect at the edge. The procedure ...
4
Data format
I'll take it as a little exercise in how to program a data reader. Have a look at the documentation:
SRTM data are distributed in two levels: SRTM1 (for the U.S. and its territories and possessions) with data sampled at one arc-second intervals in latitude and longitude, and SRTM3 (for the world) sampled at three arc-seconds.
Data are ...
3
The "Marmota" project at FBK, Trento, Italy, is offering the functionality you seem to aim for: http://tev.fbk.eu/marmota/ There are a series of publications available on that site.
Furthermore, see the related question here.
3
When you downloaded the data what format did it come in? By definition, if the data is a raster format, it can be considered 3D data, as it has a x,y,z value. If you are looking to have it extruded in ArcScene then you will want to do a few of the following things.
Assuming your data is in a usable raster format (ie: GeoTiff) then you will want to do the ...
3
It sounds like you need this as a generic solution, i.e. having all the world's elevation data available to you for any track you want to process, hence not wanting to store all the CGIAR data locally; the gpsvisualizer.com mentioned above (@Llaves) may be your best bet.
If you don't need high resolution, the GTOPO data set (1km grid) is only ~300MB for the ...
3
The folks at telascience are starting to revive the OpenAerialMap.org project which is on hold for now. They have already processed NAIP which can be found at http://hyperquad.telascience.org/naip/ They also have world coverage of Landsat done.
As far as contours, elevation, shaded relief, etc, part of the plan is to include SRTM http://srtm.csi.cgiar.org/ ...
3
The length of the arrows is determined by the magnitude_map (which would usually be the slope). If you want the arrows to be of uniform length, you can just create a new map of ones (r.mapcalc ones=1) and use that as the magnitude map. You can then control the length of the arrows using the scale factor:
d.rast.arrow map=aspectMap skip=50 magnitude_map=ones ...
3
Is it possible to produce a decent looking shaded-relief map at 50K-scale-or-larger using SRTM3 DEM?
We had good results with this approach:
Convert original raster DEM (90 meters) to points
Interpolate points to a new raster (finer resolution e.g. 10 meters)
Create hillshade from new raster (step 2).
It was a few years ago - so I can not remember the parameters exactly. But I guess we used a spline interpolation. Spline produced very soft surfaces. ...
2
The Natural Earth 1:10m data is a good place to start, but not at the resolution of the Google Maps terrain data. If you can deal with a medium resolution dataset, then styling something like the 250m SRTM data isn't too bad, but if you're interested in something at a higher resolution, it may be worth contacting the OpenCycleMap folks and see if you can get ...
2
Do you mean 3 arc-seconds? That indicates LatLong. You will have to create a GRASS location with UTM or Lambert LAEA/LCC or another metric coordinate system and run r.inund.fluv therein. See also "GRASS GIS projection intro".
2
By default, arrows are drawn at the size of a cell and cannot be seen if the raster map is relatively close in scale. You can use the skip option to draw arrows every n-th cell in both directions if you are working with relatively high resolutions. It may be useful to disable the grid in this case, which is accomplished by setting its color to "none", i.e. ...
2
There is a command that do just what you want:
v.what.rast "Uploads raster values at positions of vector points to the table"
You need a vector file with points and a table attached to it. In the table you need to create a column to receive the values from the raster. Then run v.what.rast. It will read the raster value in the position below each point and ...
2
You can use Maperitive to download SRTM tiles automatically and unzip them. Just zoom in/out to the area of your interest and it will download all the required tiles to your disk. And best of all, it's free.
Here's a sample hillshading + hypsometric rendering generated using SRTM tiles in Maperitive:
2
Another one is Closed Contour Maps
http://www.closedcontour.com/
blog about it last week:
http://mapperz.blogspot.com/2011/03/closed-contour-sps-maps.html
(blog post relevant to GISse question not self-promotion)
2
First you should specify what kind of horizontal/vertical precision you would be satisfied with.
But let's look at this from a practical perspective:
Each SRTM3 tile has 1200x1200 cells, each cell is a two-byte integer value representing the elevation in meters. That's around 2.75 MB of raw uncompressed data.
There are 14042 SRTM3 tiles. That's cca. 38 GB ...
2
Here's what the original NASA's SRTM document says (emphasis is mine):
File names refer to the latitude and longitude of the lower left
corner of the tile - e.g. N37W105 has its lower left corner at 37
degrees north latitude and 105 degrees west longitude. To be more
exact, these coordinates refer to the geometric center of the lower
left pixel, ...
2
I think it depends on your SRTM source, but if you have the original SRTM1 .hgt files, then you should read the Documentation.
I think this part (from Section 3.0) answers your quesion:
The names of individual data tiles refer to the longitude and latitude of
the lower-left (southwest) corner of the tile (this follows the DTED
convention as opposed ...
2
I don't know the answer, because it may depend on the source of your data and any processing steps that have been applied to it, but there is a reliable way that you can find out:
Notice that the cellsize of 0.00083333333333333 equals 1/1200 (degree) = 1/20 minute = 3 arc seconds, as advertised. Let's call this c.
The lower left coordinates equal (-124 - ...
2
I do it this way:
I download srtm data from : http://srtm.csi.cgiar.org/SELECTION/listImages.asp
Also, I just checked, use ftp to download, its a lot faster than http.
Then load it in Global Mapper, re-project in to desired coordinate system and export as 32 bit floating point elevation data. (yes its that simple, 2 min job at max). I tried in ArcMap and ...
1
One way to do this is to create a new point layer that contains information about overlapping forest areas. If your point layer has an attribute 'height' and each forest polygon an attribute 'forest' which is 1 for all forest areas:
Select Vector|Data Management Tools|Join attributes by location;
Select the point layer as the 'target vector layer' and the ...
1
I'm assuming you've loaded it to an array or some similar data structure, correct? A DEM is basically a grid/raster. Your problem now is to map the lon lat coordinates the cells in the grid. As the DEM has a fixed cell size, the precision of your coordinates like say your example
-33.456 152.434
would have to be approximated to match the cells on the ...
1
When talking about any DEM, it's resolution is important. SRTM has a resolution of 90 m for non US areas.
Theoretically speaking, you can't really say anything about the height variation within that pixel. So just as PostGIS rasters (or rather All Rasters), it is the value for the entire area of 90m*90m, and not for just some specific point within that ...
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