[Feature Request]: Reading altitude from NMEA messages not only from the GPS system

[MariuszTurek-W3media]

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Please select affected platform(s)

• Android
• iOS
• Linux
• macOS
• Web
• Windows

Use case

In Android we can use useMSLAltitude flag to read altitude from NMEA messages:
https://pub.dev/documentation/geolocator_android/latest/geolocator_android/AndroidSettings/useMSLAltitude.html

The problem is that Geolocator only reads the altitude from the GPS system. In my case, my two Android devices receive messages with ID $GNGGA (instead of $GPGGA), example:
$GNGGA,113733.000,0000.4351,N,00000.7576,E,1,20,0.60,277.7,M,42.0,M,,*7F
and Geolocator does not read altitude from NMEA

Traditionally, the NMEA messages start with $GP, for example the GPS NMEA message GGA starts
with the text: $GPGGA. But because various GNSS tracking systems use different systems instead
of GPS, some NMEA messages change the second text byte. A GLONASS sometimes uses N
instead of P, so a GLONASS GGA message may come out starting with $GNGGA.

https://www.raveon.com/ApplicationNotes/AN246(NMEA_GNSS).pdf
https://openrtk.readthedocs.io/en/latest/communication_port/nmea.html

Here is an example of other Talker ID prefixes (but for a GNS message):
GA: Galileo
GB: BeiDou
GP: GPS
GL: GLONASS. When more than one constellation is used.
GN: Combined GNSS position, for example, GPS and GLONASS.
GQ: QZSS

https://receiverhelp.trimble.com/alloy-gnss/en-us/NMEA-0183messages_GNS.html

Proposal

To solve this problem, just modify the code in two places:

flutter-geolocator/geolocator_android/android/src/main/java/com/baseflow/geolocator/location/NmeaClient.java

Line 47 in eaa173f

if (message.startsWith("$GPGGA")) {

if (message.trim().matches("^\\$..GGA.*$")) {

flutter-geolocator/geolocator_android/android/src/main/java/com/baseflow/geolocator/location/NmeaClient.java

Line 120 in eaa173f

if (type.startsWith("$GPGGA") && tokens.length > 9) {

if (type.matches("^\\$..GGA$") && tokens.length > 9) {

Specific requirements or considerations

No response

Additional information or context

No response

[Wackymax]

The proposal looks good to me. I think as part of this change we should also let Android handle MSL with the latest version. The new version of Android has MSL built-in as a property on location data meaning we don't need to start a separate NMEA listener