A Appendix A
Static Navigation
This feature keeps your unit’s GPS receiver from showing the normal erratic positions when
standing still. When checked, small changes in your position are interpreted as GPS error and your
computed position will remain unchanged. For applications where you will be mapping or
navigating at walking speed or slower, it is recommended to disable this feature, so even small
changes in position will be shown.
Smooth Tracking
This feature smoothes the track generated by your unit’s GPS receiver. When checked, movement
is smoothed mathematically to reduce the seemingly jagged movement resulting from GPS error.
For unfiltered, raw GPS readings, you should leave this box unchecked. However, if you want to see
a smoother overall position (e.g. while navigating), then turn this feature on via the checkbox.
Note – Both the Static Navigation and Smooth Tracking features modify your true GPS positions
mathematically so these features should not be used when you need the most accurate GPS positions
available.
Masks
These define limits that determine when a satellite will be used or not used.
l Elevation: This is the minimum angle above the horizon that a satellite must be located before
it is used. A value of zero would essentially turn off the elevation mask. A value of ninety would
mask all satellites. A typical elevation mask setting is between five and fifteen degrees to block
tracking of those satellites potentially affected by multipath error due to obstructions (e.g.
buildings or trees). Multipath error is error to the GPS position from the satellite signal
bouncing off of objects before reaching the GPS receiver.
l PDOP: This is the maximum allowable Position Dilution of Precision (PDOP), which is a
combination of HDOP, VDOP and Time Dilution of Precision. While exceeded, the GPS data will
not be used for position calculations. This setting is advantageous when quality and reliability
of your position are of concern. Typically, PDOP values of six or greater are considered
“suspect” and therefore resulting positions are less reliable.
l HDOP: This is the maximum allowable Horizontal Dilution of Precision (PDOP), which is a
measure of the geometrical quality of the solution. While exceeded, the GPS data will not be
used for position calculations.
Note – NOTE: DOPs can not be displayed in Binary Mode, however, the DOP masks are still in effect.
GPS status voice prompt
When checked, changes in GPS quality will result in an audible message indicating the change.
Ranger Series Handheld Computer 66
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