The Autochart and Autochart Pro software run on a computer....not on the unit. You record your sonar data or export track data from the unit and then run that data on a computer......If you do some searching, camohunter has done some good tutorials on how to use this software.
The mapping generated by the Autochart software will work on the 798 ....or any other Humminbird unit that supports Lakemaster mapping.
Autochart Pro can generate bottom hardness mapping and 3D....I think it is worth it to get the bottom hardness mapping.
Autochart Live is the mapping product that runs on some Humminbird units .... see this post for some explanation of the differences. http://www.crappie.com/crappie/fishi...utochart-live/
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Looking for the one that makes it all worthwhile.