A Appendix A
Using SatViewer
Your on-board GPS receiver features a 20-channel SiRF IV GPS receiver. The typical expected
accuracy for this GPS receiver is about five to fifteen meters. It has the capability of receiving
correction signals (Satellite-Based Augmentation System, SBAS) that may improve the accuracy of
the GPS. However, these correction signals are not consistently available in all locations. The typical
expected accuracy of the GPS receiver with the correction signals is about three to five meters in an
open sky.
The GPS receiver updates its position once every second. It may take several minutes to start
tracking the first time you try to use it because it needs time to update its position and download
current satellite information from the GPS satellites. This process will occur faster in a location with
open sky.
After your unit has downloaded the current satellite information, Assisted GPS (A-GPS) will retain a
memory of the satellite paths up to 72 hours. Therefore the GPS can lock on the satellites quickly, in
less than 20 seconds in an open sky.
SatViewer provides a way to quickly start using the GPS functionality of the unit, but it is not a
stand-alone mapping, GIS or navigation program by itself. SatViewer is useful for checking the GPS
configuration and enabling advanced features of your unit GPS receiver when these settings are not
made available in other applications. When changing any GPS settings or other settings, it is
important to wait a few moments after tapping on the desired option to allow time for your GPS
receiver to implement the requested change. SatViewer communicates with the GPS receiver on
your unit to compute your current position, speed, direction (azimuth) and height. This information
is displayed at the top of the screen along with other information about the satellite signals. Speed
and direction measurements are only useful when the GPS receiver is in motion. Standing in one
position with the GPS receiver may result in inaccurate readings in direction and speed. If you are
not moving, direction is reported as "?" and speed is reported as “0”. Height calculations from a GPS
receiver are typically not very accurate. Vertical accuracy is about two to three times worse than the
horizontal accuracy). Units of measurement are only displayed in U.S. feet and heights are only
displayed in height above mean sea level (MSL).
The pages of the application are accessed by tapping the various tabs, which are laid out in index
card format. The information in each tab is described on the following pages.
Use the stylus to tap the targets firmly and accurately. Sometimes you need to repeat the alignment
procedure more than once to provide a satisfactory alignment.
Quick Start
The following steps will allow you to quickly connect to the GPS with default settings:
1. Start SatViewer by tapping / SatViewer.
2. Tap on the GPS tab.
3. Make sure the COM setting is set to COM3.
Ranger Series Handheld Computer 59
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