Thanks a lot Chris. some points: 1. Are u sure that all transmitters of this type use inverse square law? 2. If we don't know position of transmitters, can we still solve the problem in least square? maybe using dD=Di-Dj paramater or so. 3. I think we can suppose all transmitters to be from the same mark, so the fixed constant in formula.
(this subject sounds a bit off topic, regarding postgis. Do u know any better place (i.e mailing list or so) for this kind of discussions?) Best Regards Saka ________________________________ From: Chris Hermansen <[email protected]> To: PostGIS Users Discussion <[email protected]> Sent: Wed, June 22, 2011 9:39:36 AM Subject: Re: [postgis-users] Interpolation problem Oh wait. Maybe each transmitter occupies a separate xy location so you are then able to calculate distance from each transmitter using an inverse square law and finally solve for the unknown xy location? If so you should be able to first determine your constants Ki i = 1,2,3 for each transmitter in Si = Ki / (Di * Di) by doing a least squares fit on the known signal strengths vs known distances (calculated from known xy). If the fit doesn't provide small residuals / high correlation then you will probably have a hard time with your subsequent computations... On 2011-06-21 9:57 PM, "Chris Hermansen" <[email protected]> wrote: > Would not there be isolines of the same signal strength? In that case there > is no unique x,y for a given signal strength... > On 2011-06-21 9:54 PM, "Saka Royban" <[email protected]> wrote: >> yes, of course.there is a unique x,y for each triple measurements. >> This measurements are, in fact, Received Signal Strength so it means more >> distance less RSS value. >> >> >> >> >> >> ________________________________ >> From: Chris Hermansen <[email protected]> >> To: PostGIS Users Discussion <[email protected]> >> Sent: Wed, June 22, 2011 8:35:05 AM >> Subject: Re: [postgis-users] Interpolation problem >> >> >> What are the three measurements? Is it reasonable to assume that knowing > three >> measurement values tells you the location ie is there a unique x,y for > each >> triple of measurements? >> On 2011-06-21 8:54 PM, "Saka Royban" <[email protected]> wrote: >>> Hi all >>> I'm not sure whether this can be done completely via PostGIS or it needs > some >>> programming. Anyway, at this step no problem with programming if Knowing > the >>>way >>> >>> >>> and algorithm. >>> I have point shapefile (arranged like a grid) and for each point there is > 3 >>> similar measurements (obtained via 3 transmitters) and, of course, x and > y >>> coordinates. The problem is that when i have a new point with these 3 > measures, >>> >>> How can i interpolate its coordinates and specify its location? >>> Maybe helpful to say, this type of measurement is distance dependent but >>> unfortunately i don't know the exact formula. >>> >>> Any help would be appreciated. >>> Best Regards
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