[postgis-users] Interpolation problem

[Saka Royban]

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 <chris.hermansen at tecogroup.ca>
To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
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" <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
>> distance less RSS value.
>>
>>
>>
>>
>>
>> ________________________________
>> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20110622/28ce7b31/attachment.html>