[aprssig] TIGER maps what-s the problem?

[Bill Diaz]

Chris,
  See below:

>-----Original Message-----
>From: aprssig-bounces at lists.tapr.org 
>[mailto:aprssig-bounces at lists.tapr.org] On Behalf Of w0ep
>Sent: Sunday, June 11, 2006 18:03
>To: TAPR APRS Mailing List
>Subject: [aprssig] TIGER maps what-s the problem?
>
>

>I'm getting more and more confused about this Tiger Maps discussion.

>If a data source like TIGER is used, how will a programmer know
>whether there are errors or how big those errors are?
>Can a blanket statement be made that they are inaccurate
>+/- X-number of feet/meters/miles?

The magnitude of the spatial errors vary.  Some locales will have relatively
little error, while others may have gross errors.  Errors of ommission are
common as well as spelling errors, naming errors etc.  Entire streets may be
in the wrong place and with no rhyme or reason to it.

>I do understand the idea of displaying APRS objects in
>light of their self-declared precision.
>But I don't understand how that issue morphed into what appears
>to be some gripe about the use of TIGER data.

The inaccuracy of Tiger data has been well known by all APRS authors for
some time.  It seems that Jared has just learned this and is carrying on a
crusade to eliminate the use of Tiger mapping data.  

>One of the affirmative defenses against nits about the accuracy
>of the map database would be:  that's all that is available for
>free usage,  you want better data you have to peel off some
>real money.  Is this not true?

Yep, well said.  The licensing cost for accurate mapping data can be quite
steep.  Some commercial products can cost as much as a new state of the art
transceiver for a single seat.  That means each user would have to pay for
each copy he uses.

Several years ago, we were able to get Chicago Map (now Undertow Software)
to agree to provide their mapping data to APRS users royalty free, provided
they bought a copy of Precision Mapping for $50. Seems they had a ham on
staff who twisted a few arms<g>.  Originally, they used Tiger data, but
starting with version 6, they used GDT data.  Big improvement in accuracy in
many areas, but is rural areas, GDT's TIGER roots are still apparent.  

Several APRS authors purchased Chicago Map / Undertow Software development
tools and created APRS applications with the data.  The only one that is
currently using the data is UiView. 

Bill KC9XG

>Chris
>w0ep