Dave,
What an interesting question? I could not help but reply.
There are quite a few "Garmin" Cambodia maps floating around the internet.
Every one I have seen, is based on the data from Jica funded ($20 million) mapping project. This project ran for 10 years a complete Arial survey of the country was completed and a room of 50 people digitized those images.
This data would make its way around on USB sticks and in Garmin format easily copied and rebranded with yet another "Cartogaphers" (pirate) name on it. Including the official dealer for that country.
"Unauthorized use"(of data) would be the term here, I believe.
I personally tracked the entire country between 2003-2009 in search of ancient temples of the Khmer empire. In those days there were very few improved roads at all. I have great memories of re discovering hundreds of these (lost?) temples , Indiana Jones style.
Ko Ker along with most major temple sites, were accessible only by very rough jungle tracks. Unlike today.
Of course landmines were always in the back of your mind, while exploring.
My map, was never published as the "pirates" owned the market, and few people are interested in actual jungle tracks and temple locations.
Here are some samples of Real Cartographers. These are some of the maps I used, while searching for "lost temples".
Aymonier, Etienne, early French explorer, cartographer
Aymonier, Etienne
Old map of unknown origin
Government map of Cambodia
