Originally Posted by balsicas
Thanks for your reply Mr. Daugherty.
I think I placed my post in the wrong spot.
I intended to say than "using my Garmin GPS 72" with Open CPN software the ship´s symbol changes to RED color with real satellite signals (and works OK). When in Simulation mode the ship´s symbol remains black (and no movement shown).
As far as I know, GPS 72 sends the same NMA protocol sentences in Real and Simulation Modes.
¿Does Open CPN "sees" other data?.
There is a status flag in most NMEA
position sentences which indicate whether position data is valid or not. Obviously a simulated position is not valid so the status flag would indicate this. You get a similar status when GPS is first switched on until it receives fix. For reasons of safety
I'm guessing that Open CPN detects this & displays accordingly.
Here is an example of status flag in field 2 of the RMC sentence:
for NMEA 0183
version 3.00 active the Mode indicator field is added
1 = UTC time of fix
2 = Data status (A=Valid position, V=navigation receiver warning)
3 = Latitude of fix
4 = N or S of longitude
5 = Longitude of fix
6 = E or W of longitude
7 = Speed over ground in knots
8 = Track made good in degrees True
9 = UTC date of fix
10 = Magnetic variation degrees (Easterly var. subtracts from true course)
11 = E or W of magnetic variation
12 = Mode indicator, (A=Autonomous, D=Differential, E=Estimated, N=Data not valid)
13 = Checksum