Most GEOCODE can be divided into three types. Some of them are something between, and some are totally different. But these basic categorization would help to evaluate new GEOCODE.

1. Mesh-code type GEOCODE:
This type of GEOCODEs divides cover area into multiple areas by mesh, and use mesh id as a code. Many GEOCODEs take this approach.
2. Encrypted type GEOCODE:
This type of GEOCODEs use specific algorithm to calculate GEOCODE from latitude and longitude value. Code presentation is almost nothing to do with physical area, so it is hard to match code with printed map. They are designed on assumption of using computer.
3. Database assisted type GEOCODE:
This type of GEOCODEs use a database to store a part or whole location data, and use a identification key to access its data as s code. For example Navigation-Code™ uses database to store integer part of latitude and longitude degree part, and use city name as a key to recall it. Yahoo!WhereOnEarthID(WOEID)™ is 32 bit integer number that is a key to get geographic location from Yahoo! Services.
These three types have different merits and demerits.
Mesh code type Encrypted type Database assisted type
Shorter length Not Good Good Good
Readability Good Not Good Good
Maintenance ability Good Good Not Good
Figure 2; Strength and Weakness of basic GEOCODE types