[postgis-users] navigation tracks (x,zy) h

Steve.Toutant at inspq.qc.ca Steve.Toutant at inspq.qc.ca
Thu Apr 5 09:37:54 PDT 2012

select distinct lat, lon .... 
unless I misunderstood the problem...

Gery <gamejihou at hotmail.com>@postgis.refractions.net 
Envoyé par : postgis-users-bounces at postgis.refractions.net
2012-04-05 11:15
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Re: [postgis-users] navigation tracks (x,zy) h

Thanks Steve, let me explain you a bit the problem:
1. the geographical positions of these tracks were recorded with a device
without enough precision, this is, instead of having for example:

67.534221 9.988212
67.534223 9.988210
67.534225 9.988207

I'm getting:
67.534100 9.987500
67.534100 9.987500
67.534100 9.987500

So I need to smooth such thing.

2. I tried st_simplify, but the problem is that this method doesn't 
curves, I tried many values but at the end I just could get a straight 
and that doesn't reflect the curves of these tracks.

3. You're right, I'm looking for a method like moving average, I've tried
the post suggested by Bob, in fact I post that message that Bob was
referring to. However, this post shows how to smooth aircraft tracks, 
Bitner used very nicely 4 variables into his code, but my tracks just have
two columns, this is, longitude and latitude. So, I tried this code with 
success so far. I already have installed PL/R and seems to be working with
my PostGis after some examples.

4. After smoothing, I want to convert my tracks into points, this is, one
track divide it into regular points and store it in regard to the name's
track. But first I need to smooth the tracks :)

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