Re: [OpenMap Users] using census zcta files

Martin Chapman wrote:

>There are several ways of doing this. Here are a two ways to do it. If
>you send me a little more detail on how the system is suppose to work I
>may be able to suggest other ways as well.
>
>Q. Do you want to have this information show on the map as a layer, or
>do you want to get this information programatically from an x,y position
>on the map, such as lat 32.0, lon -100 is in area code 80105, or both?
>
>If you want the area code from the lat/lon you need to do what is called
>a point in polygon spatial query.
>
>1. You need to have all the points that make up a zipcode polygon
>stored in either a file (like esri shape file .shp) or a database (can
>be any database).
>
>2. If you use an ESRI shape file you can use the openmap API to
>determine whether or not the point exists within the file.
>
>3. If you use a database you can use an SQL Query to determine what
>polygon (zip code boundary in your case) the point intersects.
>
>Q. What method sounds more appropriate?
>
   2 is definitly the most appropriate. AFAIK the .shp file available
from the census has this information in it. Well, actually, that is much
more than a guess as that is *exactly* what I see when I open the file
in excel. ;) .
I have no interest in showing this information as a layer. The defined
boundaries are fine as they are given.
This is available already from the openmap API? That would be most
excellent.

--
[To unsubscribe to this list send an email to "majdart@bbn.com"
with the following text in the BODY of the message "unsubscribe openmap-users"]