Hi,
Lowrance GPS data files are stored on a PC in their "*.usr" format.
Humminbird PC stores it's GPS data in the "*.gpx" format.
Google Earth uses their "*.kml" or "*.kmz" format.
Any program that "passes" GPS data to Google Earth has to do the conversion from it's "native" format to the *.kml or *.kmz format. The difference you are seeing
could be coming from either program's conversion ~ based on it's current settings. Manually re-entering waypoints is another
possible source of discrepancy. If you can export the waypoints from your Lowrance to a PC file, you can convert them to the format Humminbird PC uses (or straight to the format Google Earth uses). You can use
GPSBable to do your file conversions or you can convert your files online using the
GPS visualizer website.
Does your Lowrance unit have a SD card slot?
Darrell