JRC JLR-7700MKII - Setting the HDOP Level

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JLR-7700 MK2 GPS Navigator
Allocation of satellites with a great HDOP
value and insufficient accuracy
Allocation of satellites with a small HDOP
value and sufficient accuracy
GPS satellites currently in communication GPS satellites currently in communication
User
User
4.6.2.2 Setting the HDOP Level
HDOP level
The term HDOP is an acronym of “Horizontal Dilution Of Precision”, which represents the positioning
accuracy on the horizontal plane for the signals being received from the GPS satellites. In other words, the
value is determined by the satellite layout, which will be one (1) under the ideal condition. A larger value
represents a lower precision. Normally, no particular problem would be expected during the equipment
operation if the value remains within the range of or less. Note that the reception quality of the signal
depends on the area of a polyhedron obtained by connecting the four satellites from which the signals are
being received. The reception quality increases as the area increases, which in turn reduces the HDOP
value toward one (1).
Memo
・ The HDOP level is factory set to “20”.
・ No position data is displayed or output if the preset HDOP value has been exceeded.
・ The IMO standard for the GPS specifies that the calculated position should not be used for accuracy
evaluation when the HDOP value exceed 4. The navigator displays the following warning message if the
HDOP value has exceeded 4, which is irrespective with the setting.
① The HDOP value shown on the SAT STATUS screen will begin to flicker.
② A flickering HDOP message will appear at the bottom of the screen in any operating mode.
Thus, the value of “4” needs to be set to the navigator when it is to be certified or subjected to the
witnessed inspection. The calculation results with the HDOP value exceeded 4 will be automatically
excluded.
The equipment offers the following three HDOP levels that can be arbitrarily set the DGPS receiver connected
to it. Select a desired level by pressing the key provided on the right hand side of the DOP LEVEL.
HDOP setting Value displayed on the screen
4 or less 4
10 or less 10
20 or less 20