[postgis-users] PostGIS as a solution for non-geographic x-y or temporal data ?

Lee R sregdoreel at gmail.com
Wed Aug 27 09:38:07 PDT 2014

On Monday, August 25, 2014 4:46:11 AM UTC-4, Rémi Cura wrote:
> You want to map your dimension
> (time, note_pitch) to (X,Y) ?
> It seems really difficult to achieve if for instance you would consider a 
> C and a C up an octave closer than a C and a D.
> And if you consider
> (time,note_pitch) to (X=time, Y = [A-G], Z = [1-8]) ,
> Lot's of function in postgis doesn't work well with Z.

Fortunately we can map musical notes as 1-12 instead of A - G, or for that 
matter 1-88.  As "vectors" the notes can range from -88 to 88 (keys on the 
piano), bounded somewhat by abs( vector1+vector2+vector3 ) <= 88. 

In other words instead of an X,Y coordinate system, a musical note is 1 
dimension (y), time the 2nd dimension (x). Analyzed as a directed path 
(geometrically left to right .. ) the query would be analyzing time instead 
of a physical "x" coordinate (i.e. longitude).

So if "X" is time & "Y" is pitch, can I quantize time by arbitrarily 
discrete amounts & still get usable results? Say for example we establish 
the 1/32nd note as being the smallest duration, then everything would be an 
integer multiple of that. It's surely not a perfect model, but a cartesian 
reduction of a certain problem for quick analyses. 

An example of what I'm thinking: Using multilines, it could be possible to 
observe where a melody & it's counterpoint harmony cross over. Or draw a 
chord as a polygon & see where a melodic line crosses through it.

I wondering what other types of metrics I can derive from a cartesian 

For instance, I gather PostGIS can find polylines ranked by similarity? If 
so this could be superior to my trigram dictionary attack method, or 
bothering with an FP-Growth algorithm.

> Moreover, distance between geometry (serei of not ein your case) in 
postgis are rather limited to 
> _what you can come up with 
> _*ST_HausdorffDistance*() 
> (you could use R to create your own distances)

TY for the pointer. 

I'm very much considering using R as a stored procedure language to work 
over these data.

> I'm not an expert but lots of work in GIS rearch is devoted to time 
serie, mainly GPS trace (X,Y,Z,timestamp).
> It seems that Grass GIS has a module for it : 

Yeh, that's the USACE GIS db. Another thing to look into... :)


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