What I am given to undertand about the map cards created:
Again, many things to confirm I think, but, my best understanding (from Wayne and others as well as some personal insight into contour mapping that I had failed to consider until late last night):
Both AC Live and AC PC (AutoChart Standard/Pro PC Software) use sonar data.
I strongly suspect AC Live uses only/mostly the basic depth data (and a simpler algorithm perhaps as well); it does this dynamically at the unit, takes that sonar data, makes its calculations and writes a MAP file, a Lake Master map file to be exact (according to sources).
For AC PC you first create the sonar recording - and this contains ALL the sonar information, which I gather also includes signal response strength and similar data that allows the algorithms on the AC PC to interpret additional information such as bottom hardness and such.
Once the sonar recording is made and written to an SD card (not a ZLC), it is loaded into the AC PC software which runs a likely more resource intensive set of algorithms to generate a MAP file, again a Lake Master map file to be exact (maybe slightly better contours due to more complex algorithms but doubt much as contour generation from a give set of point elevation data is not terrible complex by modern standards - I helped write some for Engineering back in the late 80's) with (and I am not sure if this is part of the Lake Master format or a supplement) additional data, at least in the case of the pro version, such as bottom hardness.
What is written in both these cases is a Lake Master Map file (but that is a little fuzzy, explain shortly). In the case of AC Live that is the only result, the sonar data has not been saved anywhere so you have the generated Map only. And based on the response from HB it is encoded/tagged/locked/whatever (lots of ways to do this) such that only another AC Live capable unit can use that file. The fuzzy part is that perhaps it is not a true LM Map file since it can't be read by just any LM compatible unit, or it is and is locked or whatever, not sure it matters.
In the case of AC PC, a true/non-coded/whatever Lake Master Map file is created. That can be used in any LM compatible unit I understand. I am also led to understand that AC PC will NOT simply read back in that data from the MAP card, for sure in the case of the AC Live created map card according to HB, and I think likely neither. - next post possibly some insight as to why....
Some thoughts on why...for some of this:
That actually makes some sense in terms of license issues. If one could just read in LM map data and then write it back out to a ZLC one could create multiple copies of a licensed LM product; which given they own both and the ZLC's are pricey to begin with it actually might not be a bad idea for them I think but whatever.
Also, thinking about it, makes since from an algorithm standpoint too. Most of the better contour generation algorithms are not fully deterministic (non-reversible). That is, knowing point depth/elevation data (sonar data for instance) one can calculate a contour, but it is based on a best interpolation which takes into account many surround data points, per a specific algorithm (and there are several). What this means then is you can get contour data from the sonar data but you cannot derive the actual original sonar data from the contour data, only a representation of the sonar/point data could possibly be calculated.
Expanding on that further if the purpose was to continue to then add new sonar recording data each time to calculate a better and better map, a reverse derived representation of the last set of sonar data would each time increase the error in the next set of derived contour data (sometimes that error can work to make the contours more accurate to actual at a particular point but for most of the map, definitely not.
However, if each time a new set of sonar recordings is added to existing sets of sonar recordings and then the algorithms now run on yet more original actual data (rather than reversed derived) there is no additional error introduced and the final results will only get more and more accurate with more and more sonar recordings (assuming they are each done as correctly as possible of course).
Simplistic example; if you are asked what is the average speed of vehicles in a particular stretch of highway, you can calculate that based on 2 observed cars: one at 50 and one at 68 for an average of 59. You go back next week and watch 2 more cars and they are 70 and 82 lets say. If you use all four data points and simple average, the average is 67.5. If you use the 59 with a weight of one unit (since in our sonar case you don't know how many cars/data points were used to calculate that average, all you have is the result) you get a simple average of 70.3. You can easily extrapolate that to a much larger number of cars, etc. and see the error could be even much larger....or smaller, but no way to know - and I forget the math/statistics as to why but basically it works out that the VAST majority of the time it make it worse, or maybe that's Murphy's law not math. Take it one step further and get two more cars at 79 and 79. The actual average of all 6 cars would be 71.3 but if you again just used unit weight of one each time as you add more data, the avg would be 76.1, an even larger error.
I'd like to believe this is the main reason AC PC does not generate maps from a combination of maps and sonar data, but if one JUST used the map data to then reverse derive the input sonar data to then re-derive the map, it would be very close (NOT exactly the same however due to the type of math involved!). So it would seem clear that it is also based on licensing issues. Either way however, I do now feel that the way they are doing it is mostly to our benefit. That said, not sure how that can apply to a map created solely with AC live that one would like to copy to another card; but if it truly is an actual LM map card at that point perhaps it would open the door to people making illegal LM copies too and perhaps that is why.
Wow, I had long since forgotten most of that and now with Wayne's input and activating some long dormant memory cells.....it's actually starting to make sense......in my mind at least.
If I have misstated or not used the correct math terms I do apologize, it has been a long time!
And our last qualifier again: THIS MAY ALL BE WRONG/INCORRECT/BS. :thumb up2:
