Some javascript/style in this post has been disabled (
why?)
Good Afternoon,
How can I define a Mercator_2SP projection in Geotiff?
For many years (as far as I can tell) we have produced a
header with the
ProjCoordTransGeoKey set to CT_MERCATOR and both the ProjScaleAtNatOriginGeoKey
tag (set to 1.0)
and the ProjStdParallel1GeoKey tag (set to the required
Latitude) as parameters.
ListGeo records both these tags in the header, but in its
interpretation section records it as a CT_Mercator projection with a ProjScaleAtNatOriginGeoKey
of 1.000000. (No mention of ProjStdParallel1GeoKey).
We have successfully displayed this data correctly georeferenced
(as we see it) in several viewers (CARIS HPD and Geomatica Freeview for
example), but version 9.1.3 of ArcMap seems to ignore the standard parallel,
and displays the data using Scale at Natural Origin.
I can see that the definition of the coordinate system is
ambiguous and I have tried to amend the GEOTIFF header (using geotifcp) to
remove the ProjScaleAtNatOriginGeoKey from the header. ListGeo now records the
tags as I would wish, but still interprets it as a Mercator_1SP projection with
a scale factor of 1.000000.
Is this expected behaviour? I can obviously calculate
a corresponding scale factor for the Latitude of true scale, but this seems an
unnatural way of defining a Mercator projection.
Can anybody point me in the right direction?
Thanks,
Ron Russell
ICTS (Application Software Group 1)
UK Hydrographic Office
Telephone: +44(0)1823 337900 ext 3798
mailto: [hidden email]
********************************************************
The contents of
this e-mail and any attachments are the property of the United Kingdom
Hydrographic Office and are intended for the confidential use of the named
recipient only. Its unauthorised use, disclosure, storage or copying is not
permitted and may be unlawful. If you are not the intended recipient, please
destroy all copies and inform the sender by return e-mail. This footnote also
confirms that this e-mail message has been swept by Sophos Antivirus for the
presence of computer viruses. You are however advised to carry out your own
virus checks.
********************************************************
_______________________________________________
Geotiff mailing list
[hidden email]
http://lists.maptools.org/mailman/listinfo/geotiff
