how does map dowsing work? to find a missing dog?

It doesn't work other than picking a random spot to look. Dogs frequent random spots, so coincidence sometimes plays a role.

You could close your eyes and throw a dart at a map (a form of map dowsing), or you could think about dog psychology, learn what you can about where things that would interest your dog might be, and look there.

To test any method of map dowsing anyone suggests, us a globe instead of a local map. If the dowsing works, you should get an answer that is in the area your dog could make it to, not another continent or the middle of an ocean or something.

Dowsing does not work. It is coincidence only, and if you were to study the actual statistics as to how many attempts at divination actually are accurate compared to the ones that don't have any documentable results at all, you'll find that people don't remember or take into account the numerous times it doesn't work, only the one time it seems to.

This is because of the mental trick called confirmation bias - a prime example are people who seem to "know" the next song to be played on the radio before it comes on, and they say, "Isn't it amazing how I knew what was going to be played?" yet they don't take into account the thousands of times that they don't predict anything or predict the wrong song.

Attempts at dowsing follow the same trick - people will conveniently "forget" the failures, over and over, and point to a single coincidental "success" as "obvious proof" of their "powers", when it is nothing of the sort.

For data to be interpreted as actual proof, multiple, multiple tests must be performed with an accurate ratio observed between success/failure, double-blind tests, control groups, etc. all following the strict Scientific method of testing, observation, documentation, and confirmation. Nothing that any form of "divination" can produce can stand up to the harsh light of Truth and Scientific observation.

Do not use dowsing as it is divination and Witchcraft.Pray to your God for help.