Dear group
My thanks to Jaromir Svasta, Ian Thomas and Clifford Mugnier for their
contributions on the above.
I believe I have learned
1. From Jaromir Svasta
PROJCS["S-JTSK (Ferro) / Krovak",
GEOGCS["S-JTSK (Ferro)",
DATUM["D_S_JTSK_Ferro",
SPHEROID["Bessel 1841",6377397.155,299.1528128]],
PRIMEM["Ferro",-17.66666666666667],
UNIT["degree",0.0174532925199433]],
PROJECTION["Krovak"],
PARAMETER["latitude_of_center",49.5],
PARAMETER["longitude_of_center",42.5],
PARAMETER["azimuth",30.28813972222222],
PARAMETER["pseudo_standard_parallel_1",78.5],
PARAMETER["scale_factor",0.9999],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
UNIT["metre",1]]
and that "it is impossible to translate it to mapinfow.prj, because MI does
not support Oblique Conic Conformal"
BUT
that a translator may be downloaded (which I have done) and purchased
(which I may yet do) called JTSKconv from www.terris.sk
2. From Ian Thomas
that if I were to use the GIS add on for Canvas 9.0.3 I would find DWG
files supported complete with "superb drawing and illustration features".
3. From Clifford Mugnier
Before he contributed I had consulted his paper
http://www.asprs.org/asprs/resources/grids/01-2000-czech.pdf
which helped me frame my original question
I learned "Krovak Oblique Conic is a conformal projection" and "
transformation from one conformal projection to another may be accomplished
by using several common points to both projections. As long as the
difference in scalars is small (such as between UTM and the Krovak Oblique
conic, you can transform one X-Y coordinate system into the other with a
dX, a dY, a rotation, and a (small) scalar."
Mindful that a (my) little knowledge is a dangerous thing I now propose to
confirm my suspicion that the maps I have are one singular UTM and the rest
S_JTSK by comparing coordinates in both with some calculated with JTSKconv.
Using bunch of equivalent coordinates I may then proceed to create an
affine tranformation using Encom's Discover in MapInfo.
Regards and thanks
Brendan O'Donovan
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