Spectra Precision MobileMapper Field & Office Software - Manual (Page 66)

English
58
Recommendations
for E-Compass
Calibration
The E-compass being a very sensitive sensor, Ashtech
recommends you adhere to the following recommendations.
• Calibration should always be performed:
– Outdoor, not indoor.
– On a flat horizontal surface, not in your hands.
– From within MobileMapper Field rather than from
within MobileMapper Today.
– In the same operating conditions (i.e. same backlight
level, with/without SD card) as those you will work in
later when you collect your GIS data.
For screen backlight, this means the two options
controlling the backlight function on the
Battery Power
tab of the Settings window must be cleared for the
calibration phase, but also as long as you need to use
the e-compass. (The
Settings window is accessible from
the third icon on the MobileMapper Today toolbar or
through
Start>Settings>System tab>Brightness icon)
• During calibration, make sure all compass sectors become
dark blue.
• Always recalibrate the E-compass in the following cases:
– After changing the batteries.
– Whenever you suspect the E-Compass to deliver
incorrect values.
E-Compass Vs.
GPS Compass
In fact, the receiver has two compasses:
• The e-compass. which can be used independently by
MobileMapper Field and MobileMapper Today. It can even
be used by both at the same time.
• The GPS compass, which is the default compass used by
MobileMapper Field when the e-compass is not activated.
(The GPS compass information is a by-product of the GPS
position computation.)
Follow the recommendations below to know which compass
should be used, depending on what you are doing:
• Measuring bearings with the E-compass requires that the
receiver be held in horizontal position. On the other hand,
the GPS sensor requires that the receiver be held at an
angle of 45° from the horizontal. A good compromise is
therefore to orientate the receiver 20 to 25° from the
horizontal. If the bearing measurement is most important
to you, you can temporarily place the receiver horizontal
until you get a valid bearing measurement.