This is Navionics Sonar Charts and an example of fixing an inaccurate contour area.
This is the same lake as above- it is electric-only.
The whole lake, 420 acres, was given contour lines (interpolated) when it was first created using a few of my sonar logs.
The extended point was not recorded so there was no data to create it.
Note the waypoint co-ordinates are the same
This is the way it was:
This is the Google Earth track I did to collect the data:
This is the way it is now:
If you do this program, after your data has been processed, you are sent an email informing that it is ready to be downloaded and included with that email is the Google Earth track. I print that file so I have a record of where I have collected data and I can see where data needs to be collected.
This is a composite of a lot of tracks at that lake a couple of years ago when I first started collecting data, and everywhere that is not red is inaccurate. The whole lake will not be accurate until it is solid red.
Not long after providing that composite track map, Navionics started including the Google Earth track in the notification email.
In the words of Paul Harvey, "now you know the rest of the story"