Glossary - Sony HKDW-704 Operation Manual

Glossary

Almanac data
Information transmitted by each satellite concerning its the orbit.
Calculation mode
3D Operating mode: A three-dimensional GPS position fix using 4 or
more satellites. This mode gives the most precise position fix.
A
2D Operating mode: A two-dimensional GPS position fix using three
satellites.
2-satellite operating mode: Easy calculation method using two satellites.
This method does not guarantee precision.
Cold start
A unit starts to calculate a location when almanac data and ephemeris
data have not been collected from GPS satellites yet. It takes a longer
time to acquire satellite data, compared to warm start or a hot start.
DOP
Dilution of Precision (DOP)
Indicates the difference between the correct position and that calculated
using data received by a GPS receiver.
The dop indicators are GDOP (geometric DOP), PDOP (position DOP, 3
coordinates), HDOP (horizontal DOP, 2 coordinates), VDOP (vertical
DOP, height only) and TDOP (time DOP, clock offset only). Among
causes of dilution of the precision, there are problems caused in radio
transmission from satellites (fluctuation of radio waves due to weather
change and so on).
GDOP is calculated fixing aim to such a drift that satellites to be used for
calculating a location are placed against the location to be calculated
with less offset. The larger the value, the larger calculation error is. The
GPS receiver decides the best combination of satellites to be used based
on the GDOP value to obtain precision.
A-13
Appendix