On Fri, 17 Mar 2023 23:42:18 +0100, Reinhard Zwirner wrote:
[Timeout before a GNSS receiver receives and applies corrections]
Post by Reinhard ZwirnerSo would you recommend to wait a few minutes at start position before
setting out on a hike the track of which is to be recorded as precise
as possible?
If there are no problems with the Internet connection to the NTRIP server,
a couple of seconds (less than 10) should suffice. Depending on the type
of the receiver and the used correction data, you should see the position
status go from 3D (uncorrected) to a better state (DGNSS -> float -> fixed).
You need a program, that retrieves this information from the NMEA data
stream. The Lefebure client shows just "RTK" in the upper left corner,
IIRC, when correction data comes in.
Apart from this, you should wait a couple of minutes, anyways, if you
just powered up the receiver. Cold start time for the F9P receiver (to
acquire GNSS signals) is about half a minute in good reception conditions.
Afterwards you need to give it time to receive the almanac data for all
satellite systems supported. Typically, you wait about a quarter of an hour
after a cold start before beginning any serious measurement. If you used
the receiver in the last couple of days and didn't change your position
since the last measurement more than a couple (less than ~100) kilometers,
the receiver will perform a hot start and will have all almanacs, already.
Then, waiting just a couple of seconds should suffice.
Post by Reinhard ZwirnerThat ArduSimple device can receive at least Beidou, Galileo, Glonass
and GPS as well as SBAS signals. It is possible to switch off
reception of all these GNSS signals using ublox' u-center. Do you
think deactivating reception of some of the signals would optimize
position precision here in Germany?
Definitely: No! All four GNSS systems provide excellent worldwide position
data. Depending on obstruction (dense tree canvas is especially tricky)
you'll need any information available, to get fast and reliable positions.
I had measurements in the last couple of years here in Germany, that got
position /only/ from Beidou. The satellites of all other systems were
obstructed by trees and hills. (The same happened sometimes for any of
the other GNSS systems, of course.)
When your correction provider does not support one or a couple of above
mentioned systems, the GNSS receiver will drop any satellite of these
systems from calculating the position, all by itself.
Here is a link to the SAPOS caster table for Niedersachsen:
http://openservice-sapos.niedersachsen.de:2101/sourcetable.htm
If you want support for all four satellite systems, you need to use the
mountpoint VRS_3_4G_NI. "VRS_3" stands for the correction data format
(RTCM 3.x) and "4G" for the number of GNSS systems supported. Column
GNSS of the sourcetable shows /which/ four systems.
Bernd