Juniper Systems LandMark CE - Manual (Page 25)

LandMark CE User’s Manual 25
When a satellite rises above the horizon, the GPS receiver can then
receive a positioning signal from the satellite. The satellite then
appears in the skyplot section of the GPS screen. GPS readings are
more accurate when the satellites are more scattered across the sky.
The right side of the screen displays a bar graph showing the relative
satellite signal strengths. Each satellite is assigned an SV number
(space vehicle or satellite vehicle number). These numbers appear to
the left of their corresponding signal strength bars. A boxed number
indicates which particular satellite is being used to determine the
GPS position.
Note: Only active satellites are displayed on the bar graph, but all
viewable satelites are displayed in the Skyplot. The scroll bar on the right of
the graph box allows you to view all displayed satelites.
Latitude, longitude, elevation, and satellite quality values are shown
below the skyplot section of the GPS screen. The PDOP (Percent
Dilution of Position) and EHE (Estimated Horizontal position Error)
values are shown under the bar graphs.
PDOP
PDOP (Percent Dilution of Position) is based on the geometric
arrangement of satellites, and indicates the quality of GPS readings.
Optimal PDOP occurs when one satellite is directly overhead and
three others are evenly spaced out over the horizon. A PDOP less
than 4 gives the best accuracy, between 4 and 8 is acceptable, and
greater than 8 is poor.
EHE
EHE (Estimated Horizontal Error) indicates the amount of receiver
horizontal position uncertainty. This reading is an estimate based
on PDOP, HDOP, and other parameters from the GPS receiver. The
smaller the number the closer the estimate.
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