Here's a challenge for those of you who are willing to accept:
I know there has been extensive documentation of buffers created in the
Cosmetic Layer being elliptical. I understand that MapInfo is aware of the
problem and is working to fix it. The proposed work-around is to create the
buffers in a MapInfo table that has a projection. So if I was 'Joe User', I
might find a point layer make the layer editable, select Objects->Buffer...
and then create the buffers in the same layer as the points. Once the
buffers are created I would save the selected buffers as a new table, and
all is good right? Wrong!
When 'Joe User' does this, (ie the Objects->Buffer... menu command) MapInfo
executes the command:
Create Object As Buffer
From Selection
Into Table {sourcetable}
Width 200
Units "mi"
Resolution 50
Group By RowID
Guess what, if your layer is somewhat dispersed over the earth, the objects
on the edges are more and more deformed. Meaning: they become elliptical.
I've attached an .MBX, source code and the MapInfo table used to recreate
the problem. All this program does is compute the distance from the center
of the circle, to the nodes on the edge of the circle. In an ideal world,
you would expect to see the 200 miles from the center of the circle to each
of the points comprising the buffer. For those of you out there who are
experts in the field of projections, datums and spherical coordinates, help
me out here. I ran the same program on a version of 4.5 and the problem did
not occur, however, 5.5 really messes things up. I've got a work-around for
myself, which is slower and more time consuming, but I suggest that this is
a bug NOT a feature.
Ian Erickson
GIS Analyst
<<AllPoints.DAT>> <<AllPoints.ID>> <<AllPoints.IND>> <<AllPoints.MAP>>
<<AllPoints.TAB>> <<test.mb>> <<test.MBX>>
AllPoints.DAT
AllPoints.ID
AllPoints.IND
AllPoints.MAP
AllPoints.TAB
test.mb
test.MBX
