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ColinD

2,083 post(s)
#22-Feb-23 08:37

I imported an ERDAS .img and the only projection info shown is that it is Transverse Mercator. Now I can guess by looking at the coordinates that it is Zone 56S but I can't find anywhere that confirms this.

Bringing the same file into Global Mapper shows the following so I expect this info is all in the .img header.

PROJ_DESC=MGA (Map Grid of Australia) / GDA94 / meters

PROJ_DATUM=GDA 94 (AUSTRALIAN GEODETIC 1994)

PROJ_UNITS=meters

EPSG_CODE=EPSG:28356

How can this detail be accessed in M9?


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adamw


10,447 post(s)
#22-Feb-23 11:24

Open the image, go to the Info pane, click the button to the right of the coordinate system readout, select More. This will open the Coordinate System dialog. If the initial tab is Standard or EPSG, the details are at the bottom (JSON text). At any point you can switch to the Custom tab and see these details split into parameter boxes. (Close the dialog using Cancel just to be sure you do not accidentally make any changes.)

ColinD

2,083 post(s)
#22-Feb-23 19:31

Thanks. I did go through those steps to no avail, see the attached screenshot, the initial tab is Custom. There seems to be nowhere that shows more than just Transverse Mercator. In any case there is no "Transverse Mercator" coordinatesystem listed, only Universal Transverse Mercator Zone xx (N or S) [which is the "Name" according to the JSON text], which would be all that I needed here. The Standard and EPSG tabs just open at the top of the list.

Using build 179.0

Attachments:
ProjectionInfo.jpg


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oeaulong

528 post(s)
#22-Feb-23 20:33

So using EPSG:28356 didn't work? GDA94 is the base map type, not Latitude/Longitude. Then I would try setting it to the 28356 and see where it falls. I feel like I must be missing some info that is in front of you.

ColinD

2,083 post(s)
#22-Feb-23 20:38

Thanks, but not trying to set anything, trying to discover what the initial projection is in greater detail than just Transverse Mercator. Like which hemisphere and zone.


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oeaulong

528 post(s)
#22-Feb-23 20:40

was there a metadata file associated with it? an XML file?

ColinD

2,083 post(s)
#22-Feb-23 20:58

No, just the .img


Aussie Nature Shots

oeaulong

528 post(s)
#22-Feb-23 21:28

just tried with an .img file here. I am getting the same projection information whether opening the file with supplementary datafiles, or .img moved to a folder by itself. I do not understand where the extra data that Global Mapper is pulling is stored.

adamw


10,447 post(s)
#23-Feb-23 14:53

The screenshot shows Transverse Mercator with a center longitude of 153. That's the same as UTM zone 56. Scale X / Y and false easting / northing also seem typical for UTM. So, the coordinate system seems to be read correctly. It just isn't associated with the EPSG code. If you post the file to tech support, they will be able to check why the code does not seem to be read (it could be that the tag with which the code is supplied is unrecognized).

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