User's Manual

47
Leave SNR trails: Creates a dot on the screen for all previous
satellite positions that form a trail on the sky plot over time as the
satellite moves across the sky.
DOPs Bar Graph: displays the various Dilution of Precision (DOP)
values as explained below. DOPs are not displayed when SiRF
Binary is selected on the GPS page.
• PDOP: displays the Position Dilution of Precision, which is a
combination of HDOP, VDOP and Time Dilution of Precision.
It will always be larger than HDOP and VDOP.
• HDOP: displays the Horizontal Dilution of Precision, which is a
measure of the calculated accuracy of the solution. DOP has no
units and lower numbers indicate better solution geometry. In
general, the lower the DOP value, the better confidence you
have in the position reading from your GPS receiver.
• VDOP: displays the Vertical Dilution of Precision, which is a
measure of the calculated elevation.
Each DOP bar is color coded to indicate the DOP quality as
follows:
Green: The DOP is less than three (best).
Yellow: The DOP is greater than three, but less than six.
Orange: The DOP is greater than or equal to six, but less
than twenty.
Red: The DOP is greater than or equal to twenty (worst).
Signal vs. Satellite Bar Graph: shows all the visible satellites and
their corresponding ID numbers (PRN) ranging from 1 to 32. Also,
the PRN for any currently tracked SBAS satellite (ranging from 122
to 138) is displayed in this graph. Tapping any bar will also display
the signal to noise ratio (SNR) value for that satellite. The color of
each bar indicates the following:
Green: Good satellite signal strength. Satellite is used with
an SNR greater than or equal to thirty dB.
Yellow: Fair satellite signal strength. Satellite is used with an
SNR less than thirty dB.
Red: No signal or the signal strength is below the
minimum allowable threshold. Satellite is not used.