Re: Zip codes and Electoral districts

Posted by Stéphane Zagar on Feb 09, 2007; 3:48am
URL: http://civicaccess.416.s1.nabble.com/Zip-codes-and-Electoral-districts-tp865p876.html

I know but I'm not a magician :)

I don't see any way to get that.
My question is to know whether it's useful to be that precise. Maybe my view is biaised because I take my examples in Montreal, but a 6 digit postal code is a very small polygon. If I just want to match a postal code (a point) within a district (an area), it should be possible. No ? Is it an ugly way to do it ?

Steph

Tracey P. Lauriault wrote:

the lat long you get is a point, while the 6 digit postal code is a 
polygon!  So for the data to be useful you also need the coordinates of 
intersecting lines.


Frank Warmerdam wrote:
  

Stéphane Zagar wrote:
  
    

Hey

In fact, technically it's not complicated to get a zip code mapping with 
latitude and longitude :

H3T1A1;45.5113;-73.6162
    
      

...
  
    

H3T1Z1;45.4977;-73.6257

And I think it's not that much complicated to do the same reverse 
engineering for electoral district.

The problem is that mathematically, there are about 17 millions of valid 
combination of zip code. It take about 1 sec for my script to retrieve 
the zipcode/lat-long so if we do a basic computation it gives us 
about... 100 days to retrieve everything (and probably a lot of 
bandwidth). Even if we set the last number to 1 (what I did in my 
previous test), it's still about 2 millions valid values. And I'm not 
sure if the website I use to retrieve this will allow this (with 1 
request/sec, I can't imagine they won't see that something is happening).
    
      

Stéphane,

I'm afraid I haven't been following this thread very closely despite the
fact that it is close to my heart.  But I'd assume the terms of use for
the site do not allow you to extract their full database this way and
redistribute it.  Is that not the case?

  
    

By the way, I have a question for geostuff people (Tracey ?) : On the 
geogratis website, there are some files concerning the electoral 
districts ( 
http://geogratis.cgdi.gc.ca/geogratis/en/option/select.do?id=1169), but 
I don't know anything concerning the format (Arc Export or shape file). 
Is there a way to do something with that ? For example do a process 
what-ever to find out in which electoral district is a point (long-lat) ?
    
      

I can definitely help with this sort of thing if you want to do it.
Geo-data-wrangling is my thing.

Best regards,
  
    

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