Hi Tore
I did not remember to use the save current track command. I thought that if I recorded the sonar images on the SD card that the track and waypoints would also be recorded. I think the data will still be available on the sonar, but at the moment the sonar is several hundred miles away from me, stored in a boathouse in Ireland.
The GPS track must be present on the SD card, as it is displayed by Humviewer, and as an image on Google Earth.
Wingnutt suggests I use GPSBabel to decompose the Google Earth track into individual waypoints. I will investigate this
Thanks
Loughine