@Yann-Kerherve
Yann,
Here are some sample strings captured by OpenCPN navigation software thru USB on a Mac. Does this help?
10:57:30 (/dev/cu.usbserial-10) $GPGSA,A,3,22,14,17,19,03,01,,,,,,,4.4,2.5,3.639
10:57:30 (/dev/cu.usbserial-10) $GPRMC,145730.000,A,3834.6234,N,07604.5997,W,0.00,90.26,080525,,,A47
10:57:31 (/dev/cu.usbserial-10) $GPGGA,145731.000,3834.6233,N,07604.5999,W,1,06,2.5,16.8,M,-33.9,M,,0000*50

I am finding that Windy is simplifying my imported GPX routes. Is there any way to keep original resolution and number of waypoints?