[Roadster] Open US Map Data

[Carl Worth]

On Mon, 28 Aug 2006 19:52:15 -0300, Steven Garrity wrote:
> Does this help us at all?
> http://ransom.redjar.org/original_page.html

That looks like DRG (digital raster graphic) map data, and from what
I've found, that data seems to be readily available for download from
the USGS directly already, and free of charge.

The DRG data is not the most useful data for an application like
roadster, since it is raster data. It's much more interesting to start
with vector data and then have roadster generate its own lovely maps
for that. That's where the TIGER road data makes a lot of sense.

But the USGS does also make a lot of vector data available, (DLG, or
digital line graphs). This data covers waterways, manmade buildings,
roads, topography, etc. The road data is not nearly as interesting as
what comes in TIGER since, (at least as far as I could find), it
doesn't generally contain street names and addresses.

But augmenting roadster to display the other available vector data in
addition to the road data it currently has would indeed be very
interesting.

The USGS website seems to not want to be offering data just now[*], so I
can't provide a direct link to where the data is available.

The DLG data is generally available in SDTS format. That's not the
most convenient format to work with, but there is a public domain
library for reading SDTS data:

	http://mcmcweb.er.usgs.gov/sdts/sdtsxx/

I've written a sample program using that that converts sdts data
directly to an equivalent XML representation. That code could be
useful for figuring out how to work with sdts directly or perhaps
useful as a starting point for converting the data to something like
GPX:

	http://www.topografix.com/gpx.asp

I can post that code if someone would find it helpful.

-Carl

[*] http://edcsns17.cr.usgs.gov/EarthExplorer/ says:
    "...unavailable Monday, August 28 from 5:00 pm to 7:00 pm while
     maintenance is performed on the system"

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