[NTLUG:Discuss] GPS Mapping Software

[Steve Baker]

Rick Cook wrote:

> Roadmap uses the Tiger data to display detailed street information and 
> some water features. It does a good job of zooming between levels of 
> detail within the information, however, it only shows the street 
> information in little pop-up bubbles. However, this does mean that 
> Roadmap understands what each little line segment represents.

The TIGER data lists the latitude/longitude for each little line segment
(which is nominally the centerline of the road) along with the name of the
street and the range of house numbers.  The whole thing is indexed by Zip
code so you don't get confused between two roads with the same name in
different parts of the same region.

There is a *bunch* of other data (like which Indian terratory the road
might happen to run through).  You can see why this is of interest to
census-takers...but most of it is irrelevent to GPS operations.

But the data is VERY simply formatted.  It's just a very long list of
identical records with TAG/DATA/TAG/DATA.

I have a 100 line program that reads the TIGER '.RT1' file (which contains
the roads) and spits out a human-readable dump of the interesting stuff.

> I have not yet found a way to turn any of the information from either tool 
> into something useful for installing on a GPS (let alone my relatively 
> new version).

So are the formats that the GPS boxes use well documented?  How about
the download process?

If you knew that, then converting my 100 line program to generate data
for the GPS *might* be a 10 minute job.

Incidentally, if you are searching online for TIGER data, note that the
official name for the format is 'TIGR' (no 'E').

---------------------------- Steve Baker -------------------------
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