StructureMap: Making large maps with parallel passes

[SpokaneJim]

Last weekend I tried to use my Lowrance HDS 8 Gen2 to make a StructureMap of a rather large area. Length of the shoreline I wanted to map was about 1/2 mile long. I wanted to map out from shore about 700 feet. Given that I had my side scan set to measure out 50' to each side of the boat to eliminate the dark / black fringes of my side scan live view, I'd get 100' total width per pass, requiring me to make about 7 parallel passes of the shoreline.

Not knowing any data limits I may run up against, I thought I'd try making this one big map and see what happens. I successfully started to log my sonar data to my SD card, and was watching the live view of my StructureScan trail behind my boat icon on my HDS screen. I got to the end of the first 1/5 mile long pass (I was traveling about 5 MPH) then I did a U turn & started to parallel my path back to the beginning area of my first pass. I was using the live view of my structure scan to make sure I wasn't overlapping my each pass of my several planned parallel passes. Well I got about 1/4 mile (1/2 way) back to my starting point, and the end of the live view came by me in the opposite direction. This left me with no live view visual on which to parallel to to ensure I wasn't overlapping my passes. I stopped my recording, and was able to convert my SL2 sonar log to a SMF structure map file and overlay it on my chart. However this exercise brought up several questions:

1) What is the best way to create a map of such a large area? Should I have made one pass, converted it to a structure map file, then while viewing this saved file as an overlay on the chart, used that as my guide to parallel my live view up to & made my 2nd pass? (Then continue the process for the final 5 passes.) Or is there a way to make my several passes as one single event?
2) Is there a limit to the file size of a StructureMap file? ie... could I have traveled several miles down the lake without worrying about a parallel pass and created one very long SL2 file to convert to a SMF file? If there are file size limits, what physical area approximately would this represent? (A 100' wide path by how long for example?)
3) Similarly, is there a file size limit to the StructureScan file (SL2 file)?

[REW]

What does Lowrance say on the question?
REW

[mike4cobra]

I use the range rings on the gps as my guide. I made a dummy pass with out recording and flipped around and watched how many feet I wanted to be off my last trail. I then used the distance from the trails as the live structure scan was dissapearing.