Genma Saotome, on 10 April 2015 - 08:51 PM, said:
Got it.
Good that it can deal with a number of different projections... bad that it cannot deal with the current U.S. standard (an .img raster file). What he can do is read 1 degree U.S. data from 20 years ago. Fairly crude resolution. Current data has a resolution of 1/9th degree which is vastly more accurate when turned into terrain.
Payware.
Well... it looks much like DEMEX for Tranz.
He's been at it for 10 years now... looks to be slowing down a bit on the upgrades.
Below is an excerpt from the current documentation. Website may have old references. Actively maintains patches, for example the latest patch for 2.51 01/24/15 . Great support usually answers user inquires within a day or 2 .
NED
US Geological Survey DEMs are named National Elevation Dataset NED and are
produced in resolutions of 1 arc sec, 1/3 arc sec and – for some areas – 1/9 arc sec. They
can be downloaded via the USGS National Map Viewer
http://viewer.nationalmap.gov/viewer/ (01/2014). The user is offered a navigable map to
zoom to the area he is interested in. Next, he selects NED DEM data product and
resolution from which the server then composes the download from prefabricated
packages of 1 x 1 degrees (15 x 15 arc min for 1/9 arc sec).
TransDEM can directly read NED in ArcGrid format (= ESRI Binary Grid), in Grid Float
(ESRI float grid) or IMG (ERDAS Imagine). These are selectable data formats offered for
a download. TransDEM internally converts the NED data from Plate Carrée pseudo
projection to UTM with a user adjustable raster width.
Note: 1/9 arc sec resolution is supported by TransDEM from version 2.1 The downloads
will be huge. 9 times as big as for 1/3 arc sec and 81 times as big as for 1 arc sec for an
area of the same size.