Coordinate System Differences

[andrewgmurphy]

Could someone tell me what the difference between these 2 co-ordinate
system strings means

coordsys Earth Projection 8, 104, "m", -8, 53.5, 1.000035, 200000,
250000

CoordSys Earth Projection 8, 42, "m", -8, 53.5, 1.000035, 200000,
250000

The 2 ellipse seem to have the same scales and origins but the number
104 and 42 are different.

Andrew

[e.j.h.polle]

Hi Andrew,

The second string you give - i.e. CoordSys Earth Projection 8, 42,
"m", -8, 53.5, 1.000035, 200000, 250000 - is the Irish Grid (EPSG:
29902). For more information, see: http://www.epsg-registry.org/

In the user guide you can find more information about the parameters
applicable to each projection, which are listed in the order they
appear in the relevant coordinate system lines in the MAPINFOW.PRJ
file.

MapInfo Professional 10.5 USER GUIDE:
Chapter 14: Working with Coordinate Systems and Projections
Appendix B: Elements of a Coordinate System

The parameters you are asking about - the numbers 42 and 104 - refer
to the datum used. (The datum is established by tying a reference
ellipsoid to a particular point on the earth.)

Number: 42
Datum Name: Ireland 1965
Area of Coverage: Ireland
Ellipsoid: Modified Airy

Number: 104
Datum Name: World Geodetic System 1984 (WGS 84)
Area of Coverage: Worldwide
Ellipsoid: WGS 84

HTH,

Egge-Jan

[Nomeneta Saili]

104 refers to WGS 84 datumn. Basically those numbers are codes for different datums. Look in the manual for their corresponding datums.

--
You received this message because you are subscribed to the
Google Groups "MapInfo-L" group.To post a message to this group, send
email to mapi...@googlegroups.com
To unsubscribe from this group, go to:
http://groups.google.com/group/mapinfo-l/subscribe?hl=en
For more options, information and links to MapInfo resources (searching
archives, feature requests, to visit our Wiki, visit the Welcome page at
http://groups.google.com/group/mapinfo-l?hl=en