New answers tagged dem
1
And also with GRASS GIS, SAGA GIS, alone or with the Sextante plugin in QGIS, or R with with other geospatial packages, even with Python (with GDAL/OGR module), or GDAL from the command line, see Clipping rasters with GDAL using polygons but also only with QGIS:
To extract the z values after 2) Go to Raster menu,Conversion sub menu,convert, and choose, for ...
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R and Fortran will read an ArcInfo binary grid directly, with essentially no extra processing, so skip the middleman: you don't need QGIS or anything else.
These datasets consist of two files. One is an ASCII header file with .hdr extension, formatted to look like this:
ncols 1133
nrows 1415
xllcorner 686280
yllcorner 4179990
...
0
The most basic method to calculate the change in DEM volume for each pixel is
v = (DEM2 - DEM1) * A, where A is the pixel area. The total volume change is the sum of all resulting pixel values.
It seems to me that method 2 does exact the same thing. If it didn't work with any of the three methods, then you should consider changing your tool for this ...
2
There is no "best Suitable Algorithm" for what you want because it depends on the result you want to get
You can choose a method whose resulting surface passes more or less exactly through the input points (TIN, Natural neighbour, Spline) -> "angular" surface
you can choose a method that smoothens the surface according to various criteria (Inverse ...
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To smooth the hillshade, I used the focal statistics tool (in spatial analyst) with a 5x5 moving window. This can be done more than once until you're happy with the results. But as @Francesco mentioned, the hillshade will look sort of grainy on the monitor at this scale in ArcGIS. A good work around is to export map as a high res image to see the details ...
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What you want to do, is quite easy. The high level steps can be as follows:
Using Raster calculator or the Con geoprocessing tool, reclassify the raster into three classes: null for oceans/water, 1 for below 2000 m and 2 for above 2000m.
Using Raster to Polygon tool, create a featureclass from this raster.
Intersect the output of 2, with your countries ...
1
The GRASS tutorial looks like the ticket. Following along your steps, are you converting the contours to raster somewhere between 1 and 4?
Last paragraph in the About section:
A number of the r.surf.* modules want the input data to be in raster
form already, so we rasterize the contour lines, using the level
column for the height values. Also some ...
1
The best is to resample the raster and have hillshade models of different scales. 90m resolution of the whole US will shade correctly but when you view the whole image the resampling algorithm for viewing in the screen will/might cause pixellation. If you view at about 1:1 screen scale you should see a good hillshade.
Also hillshading does not work really ...
2
An alternate approach to the proposed DEM extraction, assuming you have Spatial Analyst, would be to:
Use the 'Slice' tool with the "EQUAL AREA" method and 5 or 10 zones.
Then you could either:
a) Re-classify the Slice output to create a mask to extract your DEM
-- or --
b) Use it with the 'CON' tool or Raster Calculator to mask out your DEM on the top ...
2
DEMs have 1 band which hold elevation values. For comparison, a color image has three bands (Red, Green, Blue). You can check information about any raster dataset by right-clicking on the layer > Layer Properties > Source. Other particularly useful information located here include pixel depth, cell size, coordinate system, and format. Make sure to set ...
1
Yes, I would use ArcHydro. I found a document on this page a while ago, that outlines some possible workflows (from the ArcHydro Team). There have been some changes compared to ArcMap 10.0 so for me it was quite useful.
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You should look into the Soil Water Assessment Tool (SWAT) for this type of analysis. It really depends on the soil types in your area along with temperature and topography. There are simpler ways to approximate your runoff (USLE method or the rational method), however it would be better if you could get more information.
http://swat.tamu.edu/
Good luck!
0
First I would suggest searching if already there's a tool that can make what you want.Grass for example has an extensive array of hydrological functions. If you provide a rough example on what you want to do (what do you mean by 'textfile'?) we might be able to suggest you where too look.
Python is quite powerful and it can do what you want, but don't ...
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As a geologist, I often use this technique to make geological cross section in pure Python. I presented a complete solution in Python: Using vector and raster layers in a geological perspective, without GIS software (in French)
I present here a summary in English:
to show you how to extract the elevation values of a DEM
how to treat these values
If ...
1
The current approach for gridded/point data is Web Coverage Service or WCS. This is well supported in a range of commercial and open source servers (e.g. GeoServer), and also has pretty good support at the client level (e.g. owslib)
As you've shown in your updated question, access to WCS is a lot like WMS or other OGC services.
There probably isn't as many ...
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From the comment earlier
Bike hike has the ability to parse gpx from a web location and renders this on the google map but also creates Elevation and Gradient profiles:
Miles and Kilometers supported
Other options:
Add Course-point
Drag edit mode
Reverse the Route
Map Size
This is an Example of a trail up Snowdon Mountain in North Wales.
...
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You can do this with ArcGIS 10.1.
run GPX to Features tool (converts GPX files to points features class)
run Points to Line tool (converts points FC to line FC)
run 3D Analyst tool: Stack Profile (creates a table of elevation AND with the optional output graph, provides the profile as a graph)
So you'll need ArcMap 10.1 basic /w 3D Analyst.
4
For a Python approach, try gpxplot available from code.google.com. The script is available here and the online interface is located here.
Try using GPS Visualizer. The profile tool looks like what you may be interested in.
Or, Maplorer: View GPX file on map + elevation
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By default, QGIS does not calculate the full range for a raster. The range it calculates by default is 2% - 98%, see the 'Cumulative count cut' option in the 'Load min/max values' section of the dialog box. This is just the first option, which is why (I suspect) it is the default.
To get the full range, choose the option below it marked 'Min/max', then ...
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I just had the same problem as you but had a different solution.
In scene properties I changed the "Vertical Exaggeration" to "Geographic"
(i know the question was asked a while ago but this offers another explanation.
(Im using Arc Scene 10.1)
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