GPS TrackMaker Reference Manual page 125

Warning: Area calculation is possible only if the segments are between the 80ºS parallel and the 84ºN parallel.
The picture shows how the program calculates area for open geometric figures. The end segments are
always considered closed for area calculations.
Avoid Tracklog segment crossings. The figure shows the results if this is done. The area calculated by the
program will be not the real area.
Sub metric accuracy is only obtained with topographical equipment like Total Station or Differential GPS that cost
much more than a small handheld GPS. So, for tasks that demand accuracy, the handheld GPS must be used only
as a support tool and not as main equipment.
The area calculation is accomplished without considering the altitude differences. So, only the horizontal projection
will be considered for area calculation purposes.
Occasional changes in the datum can produce variations in the area calculation. This happens because each datum
may have a proper value from the Earth semi-axis and of its flattening, it can be seen in
specific datum of your area.
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Datum Table. Use the