Someone several weeks posted a question about lake maps for Humminbird units. At the time, I was already looking into the ChartSelect option with Humminbird which is where you can buy an individual lake map. I thought I would pass along my experience. I already had a Navionics chip and there is nothing wrong with Navionics as it gives good detail but I want to use this chip in another unit. I fish Clarks Hill most of the time so I was interested in just buying the single map at lower cost.
The first thing I had to do was upgrade my units software so it could accept the map. To do this, I had to buy a SD card, download the software and then install it. I did not lose any waypoints but it does reset everything else to factory defaults. Next I had to install a new SD card in the unit and "format" it. The next step was take the formatted card and then buy the lake map ($29), download it and the software to my computer, and then put it on the SD card. I could then install the card in my unit and the map worked fine. One downside is that only one map can be install on a card which was not a problem for me, but if someone wants two or three lake maps, they would have to install on different cards and then change them out when they went to a different lake.
Personal preference, but I do like the LakeMaster map a little better because it has some features my Navionics map does not have. You can select a depth target and range and make that a different color. You can also put in a lake level offset which is going to come in handy on Clarks Hill. Bottom line is it works and is cheaper if you only fish one or two lakes but it is much more complicated than just buying the full price LakeMaster or Navionics for multiple lakes already loaded on an SD card. Sorry this is so long and I hope I did not bore you too bad.