New answers tagged elevation
TRI (Riley 1999) and TPI (Jenness 2002) are similar, but different. To calculate TRI and TPI using ArcGIS 10.x... Step 1: Use the Focal Statistics tool to make 2 new raster datasets from a DEM. Raster 1 "MAX") Neighborhood: Rectangle, Height: 3, Width: 3, Units: Cell, Statistics type: Maximum Raster 2 "MIN") Neighborhood: Rectangle, Height: 3, Width: 3, ...
It is hard to tell without an image, but this is probably due to a shift in plane coordinates. e.g. If you have the same mountain shifted toward the south, you will systematically overestimate the height on the South face, and underestimate it on the North face. So you end up with darker areas always on the same face. A good way to check for shift is to ...
Defining ridges vs hill/mountain tops is pretty scale-dependent. Jeff Jenness covers conceptually how to model topographic landforms in his article Some Thoughts on Analyzing Topographic Habitat Characteristics. If you poke around on his website, you can find his poster on this as well, under ArcGIS tools > Land Facet Corridor Designer. (Link is here) Jeff ...
The attribute table entries you quoted are strings. These can only be sorted alphabetically. You have to create numerical values from them in a new column of type integer or real using the field calculator with something like left( "elevation" , strpos( "elevation" ,'-'))
Creating watersheds should help you locate both ridges and hill top. Then, I would define a hill top as a local maximum, while a point on a ridge is not the maximum (there is one other point higher or equal to this point). You can identify local maxima using the focal statistic tool. another way to look at the problem is to analyse at the opposite of your ...
If you need Europe, just look for the EU-DEM, a new product that is a fused version of ASTER DEM and SRTM. http://epp.eurostat.ec.europa.eu/portal/page/portal/gisco_Geographical_information_maps/geodata/digital_elevation_model/eu_dem_laea http://www.eea.europa.eu/data-and-maps/data/eu-dem
You may want to take a look at the patched SRTM DEM from CGIAR: http://srtm.csi.cgiar.org/ Although it still contains the same intrinsic errors and limitations in coverage as SRTM, it is at least void-filled.
An improved version of SRTM data can be obtained from http://www.viewfinderpanoramas.org/. Coverage can be looked up under http://www.viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org3.htm The creator has put special emphasis on manually filling the error on icy parts of the world as described here: ...
I am not sure what resolution you are looking for, I assume high. But if you are wanting global coverage, you should looked at GTOPO30. It is low resolution, but it is global coverage.
In my opinion both ASTER and SRTM are maxed out. Nothing can be computationally done to improve the data. ASTER just has too much noise and SRTM is just very rough data. If you are going to spend money I would get the data that ESA is acquiring right now: There is a new data available here: http://www.astrium-geo.com/en/66-geo-elevation-and-dem You can ...
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