Order Tray | Contact Us | Home | SIG Lists

[aprssig] Re: Re: FindU Maps Quirky

KC2MMi kc2mmi at verizon.net
Mon Feb 7 18:17:56 UTC 2005


Ray, you should be aware that it is not Findu that is quirky, but rather
that Findu defaults to using the US Census TIGER map database. I went
through a long process with the Census folks this year, and confirmed, in
their words, that the TIGER maps "should only be used to compare relative
populations, they are NOT FOR PRECISION MAPPING OR NAVIGATION." In addition,
they are not always taken from the USGS Topo data. Some of the newer streets
are literally added to the TIGER maps by "someone drives down in their car
and estimates how far the next street is" while other come from various
other databases of known unreliability. The annual addenda and updates to
TIGER may include major changes in 50 to 200 counties annually.

Last time I checked FINDU was not using the 2003 TIGER maps, they were using
older maps with minor problems, i.e. New York City maps were 200-250 yards
incorrect, because they were based on a NYC proprietary datum which does NOT
match the WGS84 or anything like it. The 2003 maps were corrected for
this--in some but not all of the five counties in our city.

For better mapping, do not use the TIGER maps on FINDU. APRSWORLD has links
to ACME.COM where you can get your position from USGS Topo maps and
satellite imagery, and the position on those maps is radically different
from the position on the TIGER maps. (Which ACME also offers.)

Mind you, I'm not complaining about ay part of this. It's all free and it is
a marvelous effort on the part of many generous people. I just wish they'd
make the errors in the TIGER maps clearer, i.e. posting a disclaimer that
there *are* known issues with them. THe folks at US Census also told me they
are aware of the problem, and they have repeatedly asked Congress to give
them the funds to check and correct ALL of the TIGER maps. But Congress
doesn't want to fund them. If you want better TIGER maps, please write to
our CongressCritter and tell them to open up the damned wallet, this is
valuable work!





More information about the aprssig mailing list