I want to be able to track multiple objects for a school project, but I could only find the Parallax GPS module. This module is connected to the arduino tells your pc or laptop where your arduino is. But if the goal is to track more than one object you'll have to buy the same amount of arduino's as the number of objects you want to track. I was wondering if there is a gps sensor that you don't connect directly to the arduino, but some sort of chip you can carry with you that the arduino could track.
What do you want to track, with what accuracy, at what distances, at what kind of environment (indoor/outdoor), and how do you intend to communicate the location back to some master?
Our arduino will we launched to a height of a kilometer and our goal is to track anything from a car to person up to 10 meters accurate. The distance depends of the sensor we can find with a minimum of a kilometer. We have an APC220 module we connect to the arduino and to our laptop on the ground, through a yagi-antenna we will receive the radio-waves.
10 meters accurate is very well doable with GPS. So that's settled, just use a GPS receiver on all the things you want to track.
The real problem is how are you going to get the GPS data to the Arduino that's way up in the air? (and why is that Arduino there in the first place?)
1 km is quite a distance. You'll have to look into wireless communication, and that 1 km distance is the minimum - straight below - if you move 1 km along the surface of the earth you end up at 1.4 km total distance. Line of sight shouldn't be too much of an issue.
Easiest solution for tracking these objects over these distances within required accuracy: smartphone + app that sends GPS details back to your master over the mobile phone network.