What format do my waypoints need to be in to load to my unit from a SD card?
Humminbird units with GPS capabilities will accept waypoints from a SD card in the .hwr format for waypoints and routes and a .ht for tracks.
If the files are in .gpx format you would need to load these waypoints to HumminbirdPC to then load onto the SD card.
When looking at the content that is on the SD card from your computer, you will have a folder labeled matrix and within this folder will be a DATA.HWR file that is your navigation data.
If you have a file type that is not in the .hwr or .gpx format, there are some sites that will convert them to the .gpx type then transfer them into Humminbird PC to convert to .hwr. There is GPS Visualizer and sometimes you might need to use Easy GPS.
NOTE: you can easily corrupt the waypoint data in your unit by importing GPS data from other websites or individuals owning brands other than a Humminbird. You are responsible for cleaning up these corrupt files, this is not something covered by warranty.