Not only can you use old sonar recordings but you can also use old tracks as well. If you do not want, or have, the Si sonar you can use just the 2D (water depth) data to build your own maps.

The Zero Lines card is only needed to display the map data on your Humminbird unit.

I have my own copy of AutoCharts Pro and will be making maps for a couple of local guys – if they will just remember to take a memory card with them when they go fishing! So don't forget yours.