Richard,
The solution to your problem is relatively easy. One way of solving your
problem is to create Voronoy polygons around the positions of your rapid
transit stations. These polygons represent the area in which the point of
the rapid transit station is the closest. Next, execute the following query
(or something like it)
Select RapidPointID, CrimePointID, Distance(CrimePoints.obj,RapidPoints.obj)
>From RappidPoints,CrimePoints,Vorony
Where RapidPoint.Obj within Voronoy.obj and CrimePoint.Obj within Vorony.obj
The only thing that is not supplied standard with MapInfo is the ability to
calculate the vorony polygons.
But You can (and much more) with Triangulator from Mercator Geosystems.
Mercator Geosystems specialises in GIS solutions for policing. A free and
fully functional evaluation version of Triangulator can be downloaded from
www.mercatorgeo.nl
Go ahead and give it a try!
Roeland
----- Original Message -----
From: Richard Block <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, September 12, 2000 3:33 PM
Subject: MI Minimum Distance between two sets of points
> Mappers
> I have a large database of crimes (n=150,000) and a smaller data base of
rapid transit stations (n=125). For each of the crimes, I need to calculate
the minimum distance to a transit station and add that distance and the name
of the station to the database.
>
> I have done this previously using a spreadsheet, but with so many
incidents, this seems inappropriate. Distance.mbx from Korem does not seem
appropriate because it requires that a point be selected and I have 150,000
of them. Does anyone have a suggestion for an automated way to do this?
>
> Thanks for your help
>
>
>
> Richard Block
> Department of Sociology
> Loyola University
> 6525 N. Sheridan Rd.
> Chicago IL 60626
>
> 773 508 3454
> FAX 773 508 7099
> [EMAIL PROTECTED]
>
>
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