10.7 Calculating Topographical Areas
This option is available only in
GPS TrackMaker Professional®
.
The calculation of topographical area brings the area to be
measured to the local topographical surface, this way; you
obtain area values more accurately than the values obtained in
cartographic grids. For further information, see
Topographical
Surface x Cartographic Surface
.
To calculate areas delimited by Tracklogs, select the Tracklog according to
the
Data Selection
section and click on the
Topographical Area button
o
n the Tool Bar or in the
Tools menu.
The altitude window will appear, offering two calculation options:
•
Tracklogs Altitude
: Selecting this option the calculation will be done considering the individual altitudes of
each Tracklog segment. This option is useful when the handheld GPS sends the Tracklogs altitude to the
computer, or when the points of the Tracklogs have the altitude field filled in.
•
Local Average Altitude
: This option is useful when there are no registrations of altitudes in the Tracklogs. A
suggested medium altitude will always be indicated in this field, based on the altitudes of the selected
Tracklog.
Remember
: Topographical area calculation will depend on the correct indication of the local altitude. The altitude
is the altitude provided by the GPS, that is to say, in relation to the Earth’s ellipsoid. Also, use the specific datum of
your area.
The resulting calculation will be indicated in the
status bar in the lower part of the screen, in the respective
Area
Unit
, as well as in the Report window.
The calculated area can be indicated in the screen as a Waypoint. When creating it, just click on the text box of
the Waypoint
comments and with the arrow keys, choose the value. When the length and the area are calculated,
the values are registered hidden in the text box of Waypoint
comments.
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