Mark,
I note that you have used the Lambert Azimuthal Equal-Area (South Pole)
projection.
If you calculate the area using the cartesian option you get an exact match
on area (2,725,144.9 sq km)
Given that your triangle is 3,300 km by 1,700 km and originating at the
south pole and heading due north my guess is that the coordinate system is
not appropriate for the work you are doing, rather than 'broken'.
Perhaps someone with an understanding of the limitations of the different
coordinate systems would be able to enlighten us.
Cheers
Martin
===================================
Martin Roundill
GIS Manager
Waitakere City Council
Private Bag 93109
Henderson
Waitakere City
New Zealand
Ph +64 9 836 8000 ext 8344
Fax +64 9 836 8001
email [EMAIL PROTECTED]
===================================
> -----Original Message-----
> From: Ogilvie, Mark [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, 4 August 1999 12:25
> To: '[EMAIL PROTECTED]'; '[EMAIL PROTECTED]'
> Subject: MI area calculations broken
>
> I have been making comparisons of the area of various objects, and have
> found MapInfo's area calculating function to be seriously broken, at least
> in some projections (Polar Azimuthal projections).
>
> Attached is the MB code and an MBX (both are tiny) which demonstrates the
> problem. To summarise what the programme does:
> 1/ it draws two triangles of equal size,
> 2/ labels the triangles with their area, and
> 3/ displays the area in a browser.
>
> First problem: the labels don't show on the map because of an apparent bug
> in the label positioning function. You have to zoom out or pan up to see
> where the labels have gone.
>
> Second problem is the areas: one area calculated as 2,375,776 sq km, the
> other area as 5,688 sq km. Three orders of magnitude difference.
>
> I suspect the problem is related to projection. If anyone knows what is
> happening here, could you please let me know? What projections are "safe"
> and which are "broken"?
>
> Cheers
> Mark O.
>
>
>
> <<area_bug.MB>> <<area_bug.MBX>>
>
>
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> File: area_bug.MB >> << File: area_bug.MBX >>
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