Mazda CX-9 2007 Service Highlights page 547

GPS (GLOBAL POSITIONING SYSTEM) NAVIGATION OPERATION
• When using the navigation system for the first time after purchase or for the first time after a long period during
which it was not used, it may take about 5—15 min. until the current position is measured. Also, even during
normal use, it may take about 2—3 min. for measurement.
• The GPS antenna may be unable to receive GPS satellite signals when a vehicle passes through tunnels,
valleys between tall buildings, or in the mountains.
• Placing an object above the GPS antenna may prevent the navigation unit from taking measurements.
• When GPS measurement conditions are bad, the navigation unit may be unable to compute dimensions or
correct to the proper position.
• The position measurement error for GPS information can be reduced by reception conditions, the time band,
and by deliberate reduction in satellite accuracy by the United States Department of Defence. Also, under the
following conditions, interference with satellite signals may make it temporally impossible to receive signals
from GPS satellites.
— When receiving monitor channel 56 (UHF)
— When an automobile phone or cellular phone is used near the GPS antenna
• The navigation unit can locate absolute position only when the vehicle is in motion. Therefore, the navigation
unit does not correct direction when the vehicle is not moving.
• The navigation unit computes three positions (latitude, longitude, and altitude) using radio signals from four or
more satellites, called three-dimensional positioning. The more GPS satellite signals received, the more
accurate the three-dimensional positioning is performed. The navigation unit can receive a maximum of eight
satellite signals to compute a vehicle's position.
• If only three satellite signals can be received, the navigation unit uses two positions (latitude and longitude) and
the altitude calculated while in three-dimensional positioning to compute a vehicle's position. This is called two-
dimensional positioning.
• There can be as much as a 30-m +/- factor in the position detection system, even using the three-dimensional
positioning, which is highly accurate.
• The position detection system is affected by positions of the GPS satellites which send signals.
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MAP MATCHING OUTLINE
• This function compares the route shape the vehicle is travelling to map data using the GPS satellite signals,
and corrects the vehicle's position to the most appropriate road on the map data.
ESTIMATED ROUTE BASED
ON SELF-CONTAINED NAVIGATION
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ENTERTAINMENT
ACTUAL INDICATED
ROUTE
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MAP-MATCHED ROUTE
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