previous Menunext

GC Base 31

Functionality and example

GC Base 31 was implemented by Groundspeak to identify caches by numbers. As a result the function will supply the GC code, meaning the unique sequentially assigned number for each listing.

These GCxxxx numbers are based on the order in which a listing is posted – e.g. “First Germany”, the oldest cache in Germany has the number 77. At first the database used by geocaching.com used a hexadecimal code (1,2,3,4,5,6,7,8,9,A,B,C,D,E,F) with a "GC" up front (GC77 for First Germany).

But quickly the database reached the maximum of four digit hexadecimal (ID=65535 or GCFFFF). Now the system was changed to a base 31 code: 0-9, A-Z with some characters left out. There was a limitation to six characters due to the fact that most GPS units would not allow for more that six characters per waypoint. After the maximum amount of caches under this system was reached as well, the letters GC were placed in front to give the whole setup seven digits. The first cache to use this system was GC10000.

Rumor has it that the missing characters I, L, O, S and U were left out to make sure that the most common swear words wouldn’t turn up in listings. Therefor all GC-Codes are based on this special sytem of base 31.

Examples:

GC77 = ID 119

GC1A064 = ID 810501

Operation



Input
  1. Input of the the GC-code or ID. It doesn’t matter if “GC” is written up front.
  2. Choose either GC-Code to ID or vice versa.
  3. Ay Caramba!
Output
Displays the calculated result.