You ask yourself ...what different types of GPS systems are available?
Today there is a huge selection of GPS systems catering for the needs of different applications and users.
The basic units are just the plain old receiver with minimal set of features. A basic unit can be bought for around 100 dollars.These simple devices have the basic functionality of reporting the location in terms of latitude and longitude. They may also have a base map (a very high level map that contains major highways and few Points of Interests) of a region. Basic units have limited processor and memory capacity.These units are ideal for a person with low budget whom would like to use GPS for basic navigation, educational activities and fun.
We would like to classify these systems under following main categories:
More on this topic can be found at http://www.usglobalsat.com/t-gps_variations.aspx