66 G12 OEM Board & Sensor Reference Manual
ERM: Set Position Error Mask Values
$PASHS,ERM,s1,d1,d2
This command allows you to set mask values for horizontal and vertical error in
relation to one of three different positioning modes:
• Autonomous (AUT)— Sets the error masks to autonomous mode
• Code-phase differential (DIF)— Sets the error mask to code-differential
mode
• Both Autonomous and Differential (ALL)— Sets equal error masks for AUT
and DIF
The s1 parameter represents the positioning mode, d1 is the horizontal error mask
value, and d2 is the vertical error mask value. The range for d1 and d2 is 1 to 6000
meters. If the calculated 99% (3 sigma) error estimate of the computed position
exceeds the set ERM value, no position will be output. The 99% position error
estimate is three times the standard deviation values reported in the GST message.
Current ERM settings appear in the $PASHQ,PAR message.
The various ERM mask parameters are utilized based on the positioning mode the receiver is
operating in. For example, in auto-differential mode (AUT,ON), based on the epoch-to-epoch
conditions, the receiver will use the respective mask parameters based on the corresponding
positioning mode of each epoch. If the receiver is generating autonomous positions (e.g. due to the
lack of current RTCM correction) the AUT mask parameters will be used until differential position
fixes are computed, which will be masked by the DIF parameters.
The horizontal position standard deviation is derived from the individual latitude and longitude
standard deviations (GST) every epoch.
Example
Enter the following command to set the error masks for autonomous mode to five
meters for horizontal measurements and ten meters for vertical measurements:
$PASHS,ERM,AUT,5,10
$PASHS,ERM,ALL,d1,d2
This command allows you to set error mask values that are applied to all positioning
modes (AUT, DIF). Error mask values set through this command are in effect
regardless of the receiver’s current positioning mode. The various ERM mask
parameters are utilized based on the positioning mode the receiver is operating in.
For example, in auto-differential mode (AUT,ON), based on the epoch-to-epoch
conditions, the receiver will use the respective mask parameters based on the
corresponding positioning mode of each epoch. If the receiver is generating
G12RevD.book Page 66 Tuesday, April 2, 2002 4:33 PM
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