AvMap G6 - Manual (Page 29)

AvMap - 29
precision of the GPS
The Errors in the position a GPS receiver gives you are due mainly to two factors: the precision with which
the distance to each GPS satellite is known, and the geometry of the satellites. Distance errors can be
compensated for by using WAAS, and other techniques: Farmnavigator is equipped with a special waterproof
external GPS antenna with a U-Blox receiver that is WAAS/EGNOS DGPS enabled. But the maximum position
accuracy you can achieve is limited by GPS satellite geometry, that varies during the day.
The signal from each GPS satellite has level of precision; depending on the relative geometry of the satellites,
these precisions can be combined to give amplified or greatly compressed precision. A low DOP value represents
a better GPS positional precision due to the wider angular separation between the satellites used to calculate
a GPS unit’s position. The higher the DOP, the greater the possible error in the accuracy of your position.
Other factors that can increase the effective DOP are obstructions such as nearby mountains or buildings.
It is important to know the DOP value in every moment as this information helps you to understand how much
you can trust the precision of the GPS in that moment. If the DOP is bad then you could consider to wait until
the DOP gets better to start the work.
Appendix A: The Dop