I cannot see any nmea stream in the test program. It counts the readings but no data. on the parameters display I see all.
I tried to compile your program but it provides an error.
As you see the accuracy I get with the sealevel is excelent so I will continue to use it, but I really would like to know how the GPS knows this sealevel altitude, and if it is accurate all over the world or just here because this is where Erel lives...
I also wish you could supply the stream, so that it is used for debuging. I find very strange phenomena in devices that operate my program and this whould help.
Thanks.
edit: I checked here
NMEA data and it is the same definition.
here:
GPS - NMEA sentence information the same definition.
And here you'll see that other people get also confused by this issue :
SpringerLink - Journal Article