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• Store a memory point (MEMPoint)
• Store the wind direction (WIND DIR)
For more information on the Function menu, see section 3.8 Function Menu.
The Function menu of the Racing mode differs to a certain extent from other modes.
For more information refer to the Racing mode section 3.7.2 Function menu.
2.4. UNDERSTANDING GPS
2.4.1. Overview
Suunto M9i uses Global Positioning System (GPS) in determining the user’s position.
GPS incorporates a set of satellites orbiting the Earth at an altitude of 20 000 km, at the
speed of 4 km/s. The satellites send relatively weak radio signals at power levels
comparable to normal household light bulbs. So, the GPS reception gets disturbed
much more easily than, for example, cellular phone signal reception because the GPS
signals that reach the Earth are thousands of times weaker than cell phone signals.
However, due to the extreme sensitivity of the built-in GPS radio receiver, even the
faintest signals can be picked up.
2.4.2. Line-of-sight Needed
To ensure a good position measurement, there must be a line-of-sight connection
between the satellites and the receiver. This means that the objects or materials
between the satellites and the GPS receiver must not excessively attenuate the signal.
In practice, water-containing objects, such as people, trees or other dense vegetation,
can cause problems. The signals will not penetrate rocks or buildings or any metallic
materials. However, the receiver typically works well under relatively thin plastic,
fabric or wooden covers, e.g. inside boats.
2.4.3. Accuracy
To calculate a position, a GPS receiver usually requires simultaneous reception from at
least four satellites. The position accuracy typically increases with the number of
satellites being tracked but the most important factor is actually the relative geometric
position of the satellites. The best position estimate is obtained when satellites from
different directions and angles can be tracked. In other words, the less obstructed the
receiver’s view of the sky, the better the accuracy.
The accuracy also improves with the number of measurements made on the same
