Hello George,
> Most interesting. Would you care to elaborate? For example, what are
> "large distances".
A few hundred miles or more. Applications effected include aeronautical, marine,
weather,
exclusive economic zone (EEZ) calculation to name just a few. Given the international
nature of
these industries it's important that the technical short-fall is understood. I
reported the problem to
MI during v4.0!
Here's a quick demonstration of the problem:
1) Load up the basic MI world map.
2) Make cosmetic layer editable
3) Create a point on Iceland
4) Select the point and make a 1000nmi buffer around it
In some world projection it will be obvious that the shape is all wrong. However, if
that isn't
apparent, try using the ruler tool and measure from the centre to the created buffer.
It's not just
out, it's out by a lot! (up to 10% in places).
Another test is to create a buffer around a point near the poles. The resulting buffer
is oval.... not a
shape spreading across the entire "width" of the South Pole using a rectangular
projection.
My theory is that large buffer creation is not based on a great circle calculation.
Linear calculations
at this type of scale just don't work because they fail to account for earth curvature.
I've never tried this test in MapX. However, I've noticed that the circle tool in
MapXtreme gets it
right!
Regards,
Warren Vick
Europa Technologies Ltd, U.K.
http://www.europa-tech.com
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