[Xastir-dev] Re: Tiger 2003 Polygons?

[Curt, WE7U]

On Thu, 21 Oct 2004, Curt, WE7U wrote:

> Regarding OGR/reading in raw Tiger files, I've been doing some
> reading (and getting way lost) plus looking at the Python script.
> It looks like I can read in the "Polygon" and "PolyChainLink" layers
> first, caching the important data from them, then when I start
> reading in the "CompleteChain" layer I can set aside the geometries
> for those whose POLY_ID's match.  After I draw all of the
> points/lines, I can draw the polygons using the cached values.

Looks like I need to read in even more tables:  Landmarks,
AreaLandmarks, Polygon, PolyChainLink, and PIP, before I can combine
data with the vectors in CompleteChain to draw polygons.


> Advantage:  Fast, as I only have to read in the "CompleteChain"
> layer once.
>
> Disadvantage:  I'll end up with water on top of road/railroad
> bridges and the like.
>
> Another option would be to read in and cache the complete chain,
> construct/display the polygons, then draw the rest of the vectors.
> Might take a lot of memory to do this though.
>
> Anything I'm missing, or do I have the rough idea now?  I'm looking
> for both the minimal "correct" way to do it and the fastest method.
> It'd be nice to snag the "inside" lat/long point for the polygon as
> well, so I'd have a nice place to attach a label.  That info is in
> those Tiger files as well.

--
Curt, WE7U			         http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"