[aprssig] Re: APRSpoint and other map sources
Stephen H. Smith
WA8LMF2 at aol.com
Thu Dec 2 15:05:36 CST 2004
KC2MMi wrote on 12/2/2004, 12:01 PM:
> I like USGS mapping. I wish there was a $50 APRS solution that fully
> implemented APRS, and included a full USGS topo map set.
The basic problem is that electronic versions of USGS topo maps are
bitmaps (scans of paper maps), not vector images. The resulting bulk is
For example, look at Delorme's "3D Topo Quads" which are actual high-res
images of USGS paper topo maps, overlaid with Delorme's more current
vector road data borrowed from Street Atlas. It takes 13 CD-ROMS just
to cover California! Because of the bulk, they actually sell the set
for the northern and southern halves of California as separate products.
Delorme's own TopoUSA! uses the USGS raw terrain database (the so-called
DEMs - Digital Elevation Models) repackaged into a proprietary
compressed file format. [DEMs consist of millions of triplets of numbers
(lat,long,elevation) for points every 3 or 30 seconds of arc across the
U.S.] TopoUSA uses this data to generate maps that look very similar to
standard topos (brown contour lines, green patches for lowlands,
outlines of urban extents, etc.) from the raw data. It can also render
them in raised-relief-looking 3D. This non-bitmap (i.e. quasi-vector)
way of storing the data for the map images allow the relief data for the
entire US to be stored on only 6 CD-ROMs.
Im my opinion, this is the program that should be mated with an APRS
application. Since the current editions of Delorme Street Atlas appear
to use the same interface and presentation engine, discovering how to
interface to TopoUSA would probably make Street Atlas usable as well.
Currently, one could save bitmap map images from either program, at any
zoom level, with two lat/long points marked, calibrate them, and use
them as static bitmaps in UI-View, Xastir, etc.
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
New/Updated Symbols for http://members.aol.com/wa8lmf/ham
UI-View and APRSplus:
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