[aprssig] USA map sources

[Stephen H. Smith]

vk4tec at tech-software.net wrote:

>Hi,
>
>We do not do much advanced mapping down under, but I am keen to know what
>all this talk is
>about mapservers, troposervers ?
>
>  
>
"Troposervers"????  Don't have the faintest idea what you are referring 
to.    

As far as "mapservers" go, you aren't  being specific enough. You aren't 
specifiying in what context.


Are you refrerring to the  "PMap Server" for UI-View? 

If so, this is a software add-in to UI-View that allows a commercial 
CD-ROM mapping product (Undertow Software's Precision Mapping ) to used 
instead of fixed maps in UI-View.  You get a continuously scrollable 
view  of ALL of North American that can be zoomed from a 
continental-sized view, through state and county level, all the down to 
street level showing just a few blocks across anywhere in the USA or 
Canada.   UI-View treats all of this as a "single map".


Are you referring to the "Tiger Maps" produced by the U.S. Census Bureau 
or the topo maps produced by the U.S. Geologic Survey?   

The government-compiled data on these maps is in the public domain, and 
is available for free off U.S. government web sites.  (This situation in 
the U.S. is in sharp contrast with the situation in most other countries 
where private companies and users pay sizable fees and royalties for the 
use of public data.)
However the data is not in forms directly usable by most programs. It 
often requires considerable manipulation and conversion to be usable.  
[WinAPRS and Xastir can use this kind of data after downloading huge 
files from the Internet.]  

The  public-domain Tiger data and USGS terrain relief data ("DEMs" - 
Digital Elevation Models) are also the starting source used by many 
commercial maps and CD-ROM mapping products  such as Delorme Street 
Atlas, TopoUSA, Street Finder,, etc and websites like MapQuest. These 
publishers repackage the raw government data into user-friendly 
ready-to-use products and  often overlay the basic street data with 
other information such as the locations of motels, restaurants, shops, 
gas stations, etc acquired from business directory services.   Because 
the source data is available for free only in the U.S., these 
inexpensive (USD $40-$50) street-level-resolution CD-ROM products 
normally only cover the U.S.  (Recently, some such as DeLorme Streeet 
Atlas, MS Streets & Trips, and Undertow Software's Precision Mapping 
have started including Canada as well.)
    Several private companies such as GDT (Geographic Data Technology)  
take the public domain road data bases, correct them using aerial 
photos, satellite images, etc, . and then sell or lease the "improved" 
version to map publishers.  Microsoft (MapPoint, Streets&Trips and the 
Expedia website) and Undertow Software (Precision Mapping) are just two 
of the publishers that use the GDT enhanced data base.



Stephen H. Smith             wa8lmf (at) aol.com
                                                    
Home Page:                   http://wa8lmf.com

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