I have data that spreads across two UTM Zones GDA/MGA94 UTM Zone 55 and 56. I have layers such as a cadastre, roads, pipelines etc where I want to store measurements like lengths and areas in metres or some kind of metric notation, not degrees!
Whats the best way to manage this in PostGIS (i'm using PostGreSQL 8.4 PostGIS 1.5)? Should I be storing my data as GDA94 Geographic coords and using some sort of work around to calculate the measurements I require? Or is there another way to handle this?
Answer
Based on the information provided I would be looking at using a different projection which is not tied to the UTM Zones, like GeoScience Australia's Lambert Conformal Conic Projection. This will have some distortion effects but they will be minimal. The distance unit is metres. It should also get through the issue of the state crossing as all agencies are meant to be able to use this projection as GA is the primary mapping body in the country. Check with your requirements as this may be an option.
The projection is available for download if not provided from this website.
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