Re: Problem solved with the lakes

Hamish wrote:

>VMAP0 is 1:1 million scale (ie quite crude), and uses the NAD83 map
>datum on a GRS80 ellipsoid.
>
>SRTM-1 is 30m resolution, and uses the WGS84 map datum in the horizontal
>and the EGS96 datum in the vertical. (difference between WGS84 geoid and
>EGS96 is mostly minor; just ignore)
>
>
>I think for U.S. coverage (ie where SRTM-1 exists) it might be better
>for you to use TIGER data (US Census) instead of VMAP0. Use the ogr2ogr
>program from GDAL/OGR to reproject into WGS84 and convert to the data
>format you need. (VMAP0 is supported by the OGDI driver)
>see  http://www.gdal.org/ogr/
>
>probably need PROJ.4 as well for any reprojections and datum transforms:
> http://www.remotesensing.org/proj
>
>(GDAL & PROJ4 are maintained together)
>
>I know of an article to be published soon on SRTM+VMAP0 written by a
>colleague, can post a link to it here once it is in press if anyone is
>interested.
>
>  
>

That's very interesting.  Is the Tiger data available online someplace?  
Is there anyone out there interested in going through the process of 
remaping vmap0 datums to see if it helps any?  Anyone interested in 
playing with tiger data and figuring out the exact tool chain needed to 
use it in FlightGear?

I understand that the tiger data includes all the city roads?  I wonder 
if we could infer urban/populated areas based on the types and 
concentrations of roads?  For flightgear, we don't really care about the 
political boundary of some town or city in 1932 (i.e. vmap0), we care 
about the populated/built up areas.  I have people tell me (more often 
than you'd think) that such and such an area hasn't been forest for 60 
years.  We have to live with the data we can get, but it's always worth 
looking for better data or better ways to use the data we have.

Regards,

Curt.

-- 
Curtis Olson        http://www.flightgear.org/~curt
HumanFIRST Program  http://www.humanfirst.umn.edu/
FlightGear Project  http://www.flightgear.org
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