GC Codes

[+TerraViators]

I'm sure this may be common knowledge and previously explained in the forums. I was unable to find the answer in a search.

 

I understand that five characters had to be omitted when Groundspeak converted to a base-31 system, but how were the letters I, L, O, S and U chosen to be omitted?

[+narcissa]

I imagine that for I, O, and S it's because those are easy to confuse with 1, 0, and 5.

[+niraD]

Yep, that's it exactly. The original GC codes used only hexadecimal digits (0-9 and A-F). When they expanded the GC code system, the omitted characters that could be easily confused:

 

I (upper-case i) looks like 1 (the digit)

l (lower-case L) looks like 1 (the digit)

O (letter after N) looks like 0 (the digit)

S (letter after R) looks like 5 (the digit)

U (letter after T) looks like V (letter before W)

 

Personally, I would have also omitted Z (looks like 2), but no one asked me... probably because I wasn't even geocaching at the time.

[+SwineFlew]

On the older travel bugs, they didnt omitted it right away. It can be confusing. Thats why I always take pics of travel bug #.

 

GS isnt the only company that omitted it out. A lot of companies that deal with part numbers does it as well. It can be a very costly mistake when someone read the part numbers wrong. Never happen to me, but I see it too often as a CAD drafter. I always double check any part numbers with I, L, O, S and U in them. Thats why drafters always write in upper case letters.

[+SwineFlew]

Drafters are known to cross out the "0" so people know its a zero and not a "O". Same with the "Z" so they dont think its a two.

[+Kacher82]

On the older travel bugs, they didnt omitted it right away. It can be confusing. Thats why I always take pics of travel bug #.

It's not just the older travel bugs. I've seen a lot of newer ones, too, that can be confusing. I'm not sure if they ever did omit those letters.

[Mr.Yuck]

Yep, that's it exactly. The original GC codes used only hexadecimal digits (0-9 and A-F). When they expanded the GC code system, the omitted characters that could be easily confused:

 

I (upper-case i) looks like 1 (the digit)

l (lower-case L) looks like 1 (the digit)

O (letter after N) looks like 0 (the digit)

S (letter after R) looks like 5 (the digit)

U (letter after T) looks like V (letter before W)

 

Personally, I would have also omitted Z (looks like 2), but no one asked me... probably because I wasn't even geocaching at the time.

 

I think I missed that too, but I can't even remember. I believe they only had 65,000 some waypoints available under the original Hex system??

[Andronicus]

I have a TB that has a zero (0). On the TB page I mention that it is a zero, not a Oh (O) (how do you spell the letter)?

[+larryc43230]

I have a TB that has a zero (0). On the TB page I mention that it is a zero, not a Oh (O) (how do you spell the letter)?

I have geocoins that have the letter O, the number 0, the letter S, the number 5. and the number 1 in the tracking number. I don't think I have any with the letter I.

 

The rules regarding tracking numbers appear to be different from those used with GC codes.

 

--Larry

Edited July 28, 2014 by larryc43230

[+TerraViators]

Yep, that's it exactly. The original GC codes used only hexadecimal digits (0-9 and A-F). When they expanded the GC code system, the omitted characters that could be easily confused:

 

I (upper-case i) looks like 1 (the digit)

l (lower-case L) looks like 1 (the digit)

O (letter after N) looks like 0 (the digit)

S (letter after R) looks like 5 (the digit)

U (letter after T) looks like V (letter before W)

 

Personally, I would have also omitted Z (looks like 2), but no one asked me... probably because I wasn't even geocaching at the time.

Since Groundspeak uses a base-31 numbering system, they cannot omit more than five characters.

[+Lil Devil]

Since Groundspeak uses a base-31 numbering system, they cannot omit more than five characters.

Did they decide to use a base-31 numbering system because they wanted to omit five characters, or did they decide to omit five characters because they wanted a base-31 numbering system?

 

They could have just as easily developed a base-30 numbering system that omits six characters.

[+TerraViators]

Since Groundspeak uses a base-31 numbering system, they cannot omit more than five characters.

Did they decide to use a base-31 numbering system because they wanted to omit five characters, or did they decide to omit five characters because they wanted a base-31 numbering system?

 

They could have just as easily developed a base-30 numbering system that omits six characters.

They had to convert to a base-31 numbering system to accommodate new caches.

[+Lil Devil]

They had to convert to a base-31 numbering system to accommodate new caches.

That's simplistic reasoning. I was actually here when they switched to base-31. Previously they were using hex, and they could have just as easily continued using hex. They just would have gone from a 6-character GCXXXX code to seven characters GCXXXXX. And later 8 character, etc. The problem was GPS units at the time only supported 6 character waypoint names. So they effectively bought everyone another year or so by going to base-31. But as I said above, they could have used base-30 or base-26 or base-50. The point was to keep within 6 characters for some time.

 

Fortunately for most of us, within that year, GPS manufacturers came out with new units that could support longer waypoint names. As a result many switched to showing the actual cache names instead of the GC Codes.

[+GeoTrekker26]

Since Groundspeak uses a base-31 numbering system, they cannot omit more than five characters.

Did they decide to use a base-31 numbering system because they wanted to omit five characters, or did they decide to omit five characters because they wanted a base-31 numbering system?

 

They could have just as easily developed a base-30 numbering system that omits six characters.

They had to convert to a base-31 numbering system to accommodate new caches.

That does not address the question. A base-30 system would also have accomodated new caches.

[+fizzymagic]

They chose base-31 because they wanted to eliminate those characters. No other reason. I don't know of anyone else who uses it. But what difference does it make? You want as large a base as you can get without having easily-confused characters.

[+and1969]

Since Groundspeak uses a base-31 numbering system, they cannot omit more than five characters.

Did they decide to use a base-31 numbering system because they wanted to omit five characters, or did they decide to omit five characters because they wanted a base-31 numbering system?

 

They could have just as easily developed a base-30 numbering system that omits six characters.

They had to convert to a base-31 numbering system to accommodate new caches.

That does not address the question. A base-30 system would also have accomodated new caches.

 

It wouldn't have accommodated as many. Bearing in mind that the system started from GCGxxx, this meant 15x31x31x31 as opposed to 14x30x30x30 possible ID's, a difference of 68865, giving a bit of breathing space while GPS manufacturers were being lobbied.

 

Incidentally I worked on a very similar problem, replacing a software system that - among other things - allocated prefixes in the format A001 to Z999. This was for 8-character codes where the users provided the other 4 characters e.g. A12301A0. We were in the process of replacing the system, when the series was already in the V's, and the codes running out was one of the main drivers. Our new codes are AAAA-ZZZZ. This allows for a possible 456976 codes, as opposed to the earlier 25974. Again this was to cater for the limitation of certain other software that would only accept 8 character codes - our prefix, plus the 4 characters added by the user. We finally got the old system switched off when it was well past Z500. And yes, we do have an exclusion list for certain codes

Edited August 1, 2014 by and1969