Reefmaster
 

I came across this software on another forum and checked it out. ended up downloading the free trial and have been geeking out over it ever since. It allows you to log sonar data and process it. Its much like Navionics but instead of sending in the logs you process it yourself. The price of the software is close to the price of the Navionics chip, and a yealy membership.

Benefits of this is the more logs of an area, the more accurate the map is.

I logged a bunch of data on Saturday since the fish were not biting. Check out the screen shot of the Mouth of Shark Bayou.

that's awesome!! it matches the bank line so perfectly too