[Manifold-l] Projection Query - regarding Map Grid of Australia 1994, Zone 54...

[Medlin, Chris (DWLBC)]

Hi List,

I recently imported an ESRI Grid into Manifold (v 6.5 build 408) as a Surface.  The surface is a lidar derived digital elevation model of part of Western Victoria (Australia) with a cell size of 10 metres.  The projection used by this data is the Map Grid of Australia 1994 (zone 54).  Based on the Geocentric Datum of Australia 1994 (GDA94) the Map Grid of Australia 1994 utilises a Universal Tranverse Mercator projection (with 6 degree zones) with a scale factor of 0.9996 at the central meridien and a false northing of 10,000,000 and a false easting of 500,000.  Map units are metres.

What I can't understand is why I see the appearance of a 'local offset' of 495000.00 in X and a local offset of 5880000.00 in Y.  What is this 'local offset' about?  I've not come across it before with respect to this projection.  Having read the Manifold help with regards to the 'local offset' parameter, I still don't understand why these values are appearing.  If I use the Edit > Projection > Current Projection dialogue to set these 'local offset, values to zero, then the coordinates that I see as I move the cursor around the surface are clearly incorrect (eg. 22967E 19276N).

Can anyone provide some insight into this for me?

Thanks,

Chris Medlin

==========================================================
Chris Medlin
Geographic Information Systems (GIS) Officer
Resource Information - Knowledge and Information Division
Department of Water, Land and Biodiversity Conservation
Level 3, 25 Grenfell St, ADELAIDE
GPO Box 2834, ADELAIDE, SA, 5001

Phone: (08) 846 37981;  Fax: (08) 846 37900;  Mobile Ph: 0410 413 616
Email: chris.medlin at state.sa.gov.au


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