Question

Is it possible to make a checher for http://coord.info/GC49K44

Answer 1

So this requires finding all the currently active caches within an area (3 Danish counties to be exact).

There is a new API method GetNumCachesInArea which may just do it (find all the caches the user has found in the areas, subtract away any that are currently disabled or archived, then compare it against the number that this method returns.

Comments

I suspect you are trying to write a all caches in an area checker. From this checker and the API question
I have written one the weekend http://project-gc.com/Tools/Challenges?edit&scriptId=854
This challenge is unfortunate not possible because part of the island is in the same county as areas outside

Answer 2

Unfortunately it is still impossible. I i understand the challenge correctly. All traditional on Amager

 

The problem is that the northern part of the island is in København county according to PGC. It is the same county as the rest of København not on the island.

 

http://project-gc.com/Tools/MapCounties?profile_name=Target.&country=Denmark&region=Hovedstaden&submit=Filter

 

I don't know it the county map is correct for PGC. I guess it is taken from from administration level on openstreetmap 

Comments

Out of curiosity, would the new API function work with a polygon instead of a county?

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No. That method don't exits
Difference is that to count the number in a county is an fast SQL query.
To check in a polygon requiter a time consuming check if the coordinates is inside that polygon.