I finally found the reason for the incorrectly shaped voronoi polygons. It seems the Projection your points are in effects the shape of the voronoi polygons created. The points table I used to create the voronoi polygons from was in a Longitude/Latitude Projection, which created the inaccuracies. When I saved the table and changed the projection to Regional Equal-Area Projectons (North America), the new voronoi polygons from these points was correct.
Thanks to all for the help. -Bob "Karl Kliparchuk" <[EMAIL PROTECTED]> on Thursday, January 12, 2006 at 10:43 AM -0700 wrote: >I think the problem may occur at the edges, as the voroni polys are drawn >based on points. You may want to consider placing dummy points around >the edges of your data distribution in order to constrain the polygons. > >Karl > >GIS Business Manager >McElhanney Consulting Services Ltd. >100 - 780 Beatty Street >Vancouver, BC Canada >V6B 2M1 >Tel (604) 683-8521 >Email: [ mailto:[EMAIL PROTECTED] [EMAIL PROTECTED] >web: [ http://www.mcelhanney.com/mcsl ]www.mcelhanney.com/mcsl >web: [ http://www.MapsByAir.com ]www.MapsByAir.com > >>>> Robert DeRubeis <[EMAIL PROTECTED]> 01/12/06 9:32 AM >>> > >I got the same results with only 26 points as with all 15,000 so I guess >the number of points doesn't seem to matter. Something seems to be off a >little in MI Pro as to how it creates the voronoi polygons. > >-Bob > >Peter Horsbøll Møller <[EMAIL PROTECTED]> on Thursday, January 12, 2006 at 9:17 >AM -0700 wrote: >>Have you tried to create voronoi on just those two stores and approx. 30 >>stores around these ? >>This should give them same result as when you create for all your 58000 >>stores >> >> >>Peter Horsbøll Møller >>GIS Developer, MTM >>Geographical Information & IT >> >>COWI A/S >>Odensevej 95 >>DK-5260 Odense S. >>Denmark >> >>Tel +45 6311 4900 >>Direct +45 6311 4908 >>Mob +45 5156 1045 >>Fax +45 6311 4949 >>E-mail [ [ mailto:[EMAIL PROTECTED] ]mailto:[EMAIL PROTECTED] [EMAIL >>PROTECTED] >>[ [ http://www.cowi.dk/gis ]http://www.cowi.dk/gis ][ >http://www.cowi.dk/gis ]http://www.cowi.dk/gis >> >> >> >> >> >>---------------------------------------------------------------------------From: >>Robert DeRubeis [[ mailto:[EMAIL PROTECTED] >]mailto:[EMAIL PROTECTED] >>Sent: Thursday, January 12, 2006 4:41 PM >>To: mapinfo-l@lists.directionsmag.com >>Cc: Peter Horsbøll Møller >>Subject: Re: [MI-L] voronoi polgon >> >> >>I have used the Distance Calculator in MI Pro v7.8 and that gave the >>correct closest store location. But I'm wanting to assign some 58,000 >>customers to the closest store. The number of customers will vary >>depending on how many customers fall within that particular voronoi >>polygon, which is anywhere from zero and up. >> >>The whole problem seems to be the voronoi for each store is not >>representing an area closest to that store for some reason. I'm creating >>voronoi polygons from over 15,000 points. Could that be the cause of the >>problem? Has anyone else had any similar problems? >> >>Thanks, >>Bob >> >>Peter Horsbøll Møller <[ [ mailto:[EMAIL PROTECTED] ]mailto:[EMAIL PROTECTED] >[EMAIL PROTECTED]> on Wednesday, >>January 11, 2006 at 2:22 PM -0700 wrote: >>Bob, >> >>That sounds kind of strange. The voronoi for each store should represent >>the area closer to each store than to any other store - just as you >>expect. >>And therefore each customer should be within that voronoi that also >>contains the store they are closest to. >> >>Have you tried using the DistanceCalculator, that came with MapInfo 7.8 - >>or even the improved one for MapInfo 8.0 ? This tool will give you the >>nearest x stores for each customer. x can be 1, 2 or as many as like. So >>this would be another way of getting the result, you are looking for. >> >>The tool from MapInfo 8.0 the result will be represented as a line >>between the customer and the store. I'm not sure if this also is the case >>with the 7.8 tool >> >>Peter Horsbøll Møller >>GIS Developer, MTM >>Geographical Information & IT >> >>COWI A/S >>Odensevej 95 >>DK-5260 Odense S. >>Denmark >> >>Tel +45 6311 4900 >>Direct +45 6311 4908 >>Mob +45 5156 1045 >>Fax +45 6311 4949 >>E-mail [ [ mailto:[EMAIL PROTECTED] ]mailto:[EMAIL PROTECTED] [EMAIL >>PROTECTED] >>[ [ http://www.cowi.dk/gis ]http://www.cowi.dk/gis ][ >http://www.cowi.dk/gis ]http://www.cowi.dk/gis >> >>-----Original Message----- >>From: [ [ mailto:[EMAIL PROTECTED] >]mailto:[EMAIL PROTECTED] >>[EMAIL PROTECTED] [[ >>[ mailto:[EMAIL PROTECTED] >]mailto:[EMAIL PROTECTED] >>][ mailto:[EMAIL PROTECTED] >]mailto:[EMAIL PROTECTED] On Behalf Of Robert >>DeRubeis >>Sent: Wednesday, January 11, 2006 5:58 PM >>To: [ [ mailto:mapinfo-l@lists.directionsmag.com >]mailto:mapinfo-l@lists.directionsmag.com >>[EMAIL PROTECTED] >>Subject: [MI-L] voronoi polgon >> >>List, >> >>I have 2 point tables, stores and customers. I would like to find all >>the customers that are the closest distance to a particular store so I >>can assign information from the store to those customers. I created a >>voronoi polygon from the store points, then did a select statement where >>customer points are within store voronoi polygon. >> >>My problem is that I noticed in certain cases that some customer points >>fell into a store voronoi polygon, but was actually closer to another >>store. I measured the distance in MI Pro Ver 7.8 and it was not a big >>difference (8.19 instead of 7.78 miles), but wondered why the >inaccuracy? >> >>Thanks, >>Bob > >_______________________________________________ >MapInfo-L mailing list >MapInfo-L@lists.directionsmag.com >[ http://www.directionsmag.com/mailman/listinfo/mapinfo-l >]http://www.directionsmag.com/mailman/listinfo/mapinfo-l > > >[ http://www.mcelhanney.com/sig/gwsigLogo.jpg ][Image] > > >This message and attachment, if any, is intended only for the person >to whom it is addressed and may contain information that is privileged >and confidential. If you are not the intended recipient, you may not >disseminate or copy this communication. Please notify us of our error >by return e-mail and destroy all copies of the communication. >Thank you _______________________________________________ MapInfo-L mailing list MapInfo-L@lists.directionsmag.com http://www.directionsmag.com/mailman/listinfo/mapinfo-l
