Re: MI when is a centroid not a centroid?

[Warren Vick, Europa Technologies Ltd.]

Hello Marc,

> I thought that I would create two new fields in each table and put the
> eastings and northings in them, and then do something or other with buffers
> which would match up the correct town names with the town locations. When I
> did an Update Columns using CentroidX(obj) and CentroidY(obj) the northings
> came out more or less what I would expect, but the CentroidX values are
> totally wacky. The actual maps have the correct positions for the towns,
> and if I click on a symbol the Point Object dialog comes up with a
> meaningful UTM value, but the centroidX values are on the order of
> -10,000,000.  I get the same behaviour for both tables, which are in UTM
> Nad27 zone 13.

A few people have suggested that it may be your current coordinate system which is 
causing the 
problem but, since your northings seem to be correct, I don't think this is the case 
(you do of 
course need a "set coordsys table [TabName]" command to get MI out of using 
Latitude/Longitudes) With many maps using the UTM system, an offset is often 
introduced to save 
on the size of expressed coordinate. I have seen many maps for contrasting areas of 
the world 
which use this scheme. A round figure offset such as the one you gave suggests this 
may be the 
case. Try doing your table update with centroidx(obj) plus or minus the necessary 
offset.

Regards,
Warren Vick
Europa Technologies Ltd, U.K.
www.europa-tech.com
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