[Manifold-l] Projection Query - regarding Map Grid of Australia1994, Zone 54...

[Colin Driscoll]

Chris
 
I may be wrong here but the drawing can adopt the offsets of another
component- nothing to do with the projection per se. However the drawing
should be in the correct location in Australia. You can reproject setting
the Offset to zero and Local Scale to 1. You might notice that all images
have local offsets.
 
Cheers
 
Colin Driscoll
 

  _____  

From: manifold-l-bounces at lists.directionsmag.com
[mailto:manifold-l-bounces at lists.directionsmag.com] On Behalf Of Medlin,
Chris (DWLBC)
Sent: Wednesday, 8 November 2006 10:41 AM
To: manifold-l at lists.directionsmag.com
Subject: [Manifold-l] Projection Query - regarding Map Grid of
Australia1994, Zone 54...



Hi List, 

Resend of msg sent to "manifold-l at lists.directionsmag.com" on Nov 6, 2006.
Is the list working properly?  Moving right along...

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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