[postgis-users] MakeLine for geography coordinates

[Jochen Albrecht]

Fellow PostGISlers:
I am working with a world-wide data set consisting of six-hourly positions
of buoys to capture speed and direction of ocean currents. There are some
1,500 buoys, each surviving for an average of a little over 1.5 years
amounting to some 22 million location records.
As these buoys travel typically a few thousand miles, I have to use
geography rather than geometry coordinates.
My problem right now is that I do not manage to combine individual
observations into tracks. ST_MakeLine does not accept geography coordinates
and if I use geometry instead, then I run into problems with all those buoys
that at one time or another cross the date line.
Given that I work with world-wide data and I will have to analyze buoy paths
in the North as well as the South Sea (not the same buoy, mind you), I
cannot afford to stick with geometry coordinates but the set of functions
for geography is yet rather limited. Am I too early in my attempt to use
PostGIS, i.e., should I switch to other packages or can you think of
work-arounds for my tasks laid out above?
Cheers,
     Jochen

Jochen Albrecht
Hunter College, CUNY
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