[postgis-users] Interpolation problem

Chris Hermansen chris.hermansen at tecogroup.ca
Tue Jun 21 22:09:36 PDT 2011

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" <chris.hermansen at tecogroup.ca>
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" <sakaroyban at yahoo.com> 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
>>
>>
>>
>>
>>
>> ________________________________
>> From: Chris Hermansen <chris.hermansen at tecogroup.ca>
>> To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
>> 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" <sakaroyban at yahoo.com> 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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