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[aprssig] Re: APRSPoint and other map sources

Curt Mills archer at eskimo.com
Thu Dec 2 07:03:32 UTC 2004


On Wed, 1 Dec 2004, Stephen H. Smith wrote:

> I fully agree with the original poster's comment about "uglyness" of
> maps.  The raw Tiger file database, as presented in most applications
> that use it, fails to distinguish (by using different line weights
> and/or colors) between dirt roads, minor side streets, major urban
> streets, or secondary highways.

That's why the preferred maps for Xastir are the raw Tiger data
converted to ESRI Shapefile format, which you can then render nearly
any way you like using map customization files (dbfawk files).  We
have a set of dbfawk files that go with the ESRI Shapefile format
tiger data, and they render nicely.  They also render faster than
the raw tiger datafiles.


> Furthermore, for mobile non-Internet-connected operation, the entire raw
> Tiger database, as downloaded, is enormously bulky compared to the
> commercially-enhanced databases that come with Delorme Street Atlas,
> MapPoint, Streets&Trips, Precision Mapping, etc.  These programs encode
> every street and road segment in the US, including street-address
> indexing, into a total database of less than 1 GB.

We have street-address lookup as well.  Separate database, derives
from tiger data originally.  Don't remember the size, but that
particular part wasn't all that big as I recall.

Agree about the rest being a bit bulky.  I load USGS topo maps for
my entire county (7.5 minute) when I go jeeping/hunting/SAR'ing,
plus the tiger data in Shapefile format.  I don't typically need
large areas worth of maps, as I don't travel that much.  A 6.4GB
disk on a P133 with 64MB ram gives me what I need for this county,
including OS, client, and maps.


> For mobile applications, don't even mention the various bitmap
> image-oriented formats such as Terraserver images, USGS Topo map images,
> GeoTIFFs, etc.  Just too incredibly bulky for large areas compared to
> compressed vector formats.

But...  I do moving map on top of topos.  Great for 4-wheeling.


>       The points of interest (parks, museums, airports, schools, etc.)
> called out in the two products WILL be different since this information
> is purchased from completely different sources and is overlaid on the
> background map.

And our overlays are USGS GNIS points.  Something new yet again.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
  Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"





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