Just installed Garmin Quickdraw on my Echomap 73SV and it charts the lake in 1' increments as you pass over them. Really impressed at the charts. I fish Caney Res in La and no maps are available. You can go up to 10 mph and chart or it will chart will you are fishing. Was a free download. Garmin Quickdraw™ Contours Will post some pics when I can.