Re: Roughtly converting DOP to metric error

On 5 Mar, 10:28, Nick <nhop...@xxxxxxxxx> wrote:
On 4 Mar, 20:49, speleo...@xxxxxxxxx wrote:

Garmin units usually send a proprietary PGRME sentence that reports
horizontal, vertical and overall position error [...]

Forgive me, but I don't think GPS receivers can report errors in
position, to do this they would need to know their true position.

Regards, N.

In fact they should not report error in position, but an estimate of
the error.
If the signal is good, residuals are low, dop is good (and other
params) -> the estimation is good (some meters)
If the signal is low, residuals are very big, dop is bad (and other
params) -> the estimation is bad(maybe hundreds meters)
And you can mix all the situations like bad signal with good
dop... :)
A complex formula is used for the estimation.
Anyway, GPS receivers that usually have a message for the error
estimation tends to be too much optimistics :)
.