[postgis-users] Q: using the M coordinate for time

[Just van den Broecke]

Hi,

I am intending to use the "M coordinate" (as used in e.g. 4d POINTs) to 
store UTF timestamps similar as in: 
http://www-1.ibm.com/support/docview.wss?uid=swg21054384 (DB2 SE-specific).

App. usage: storing per-user live GPS points as x,y,z,m in PostGIS using 
LINESTRINGs (alt. using row per 3d point and time in column, but have to 
potentially deal with millions of points plus use/query pattern is 
mainly by track).

Questions:
- known uses for storing time in "M" (or alternatives) in PostGIS  ?
- any functions/operators to extract e.g. a specific point for an "M" 
value or a range between "M" values (e.g. time interval) ?

thanks,

--Just

http://www.justobjects.nl
http://www.geotracing.com