Dear Experts,
Now, that I've bought that ArduSimple device and use the mentioned
app there are, of course, new questions. In the app's preferences you
can choose two different file formats for the recorded position
information: nmea.txt and ntrip.txt.
Okay, GPSBabel has not any problem to convert NMEA data into gpx
format. But what about those NTRIP data? Would it be preferable to
let those data be converted into gpx data? If yes, which program
could do this? As I said: New device, a lot of new questions.
In the app's preferences you can choose two different file formats
for the recorded position information: nmea.txt and ntrip.txt.
On Fri, 17 Mar 2023 00:12:27 +0100, Reinhard Zwirner wrote:
[Lefebure NTRIP Client]
In the app's preferences you can choose two different file formats
for the recorded position information: nmea.txt and ntrip.txt.
The Lefebure client first gets the NMEA data stream of uncorrected positions from the external GNSS device via Bluetooth. It probably extracts the CGA message (basic positioning information) and sends it via Internet (Mobile
or WiFi etc.) to the NTRIP server, that is configured in the Lefebure client settings. The NTRIP server answers with correction information suitable for the current GNSS receiver position. As next step, the Lefebure client sends this correction information (again via Bluetooth) back to the GNSS receiver.
The GNSS receiver incorporates the correction information into the position calculating process and starts emitting NMEA data with corrected positions and basic information about the correction. Now the Lefebure client uses /this/ NMEA information as a basis; and the whole process continues, as long as everything stays connected and no error occurs.
Back to the files:
The continuous input stream arriving from the GNSS receiver via Bluetooth
can be saved to the logfile nmea.txt. This file can be used as input to position-aware programs. Depending on the amount of information evaluated from this file, the program reading it may just show a sequence of positions or present a lot of additional details for each position. (Like used sats, estimated precision, and so on.) The NMEA stream can, therefore, also be
used to debug possible errors in the whole process, like omitting a whole type of satellites. (Which may happen, when the correction data only
supports a subset of the satellite systems from those the GNSS receiver supports. E.g.: Just GPS and no GLONASS, Beidou etc.)
The continuous input stream arriving from the NTRIP server via Internet, OTOH, can be saved to the logfile ntrip.txt. This also can be used for debugging. Another possibility is to use it for postprocessing the
position measuring data. Postprocessing usually requires, that the raw satellite data is logged by the receiver, though. Recreating uncorrected
data from an corrected NMEA stream is not feasible.
It is /not/ possible to extract the position of your GNSS device from
the correction data. (= Not included, because the only information the
NTRIP server has about your position is the information of the CGA string
you sent. - Duplicating this in the RTCM answer would be a waste of bandwidth.) What /is/ included in the RTCM data stream is the position
of the (most likely virtual) reference station, that was used as source
for the correction data.
A free software most suitable for postprocessing is RTKLIB, btw: https://rtklib.com
So 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?
That 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?
mountpoint VRS_3_4G_NI. ...This has been my choice every time I used my new "toy".
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