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What is the difference between satellite trackers, GSM trackers, and standalone trackers?
There are many ways to determine the position of an asset but we will assume the most common application where a global network of satellite's are used. The current big three networks are GPS, Galileo, and Glonass. To make explaining this easier, we will use the term "GPS" for all three networks as the differentiation is not necessary. The first step in tracking, is determining the location of the device. This requires determining the location of the asset by measuring the distance from something else, in this case the GPS satellite's orbiting the planet. Satellites in general are purpose built for an application such as positioning or communications. The satellite payload is limited by weight, battery/solar power, rocket, etc, so each satellite is purpose built. A satellite built for positioning has an onboard atomic clock for an extremely accurate time source, and transmits this time source globally. A communications satellite has very sensitive antenna's for receiving signals from the ground, transmitting back to the ground, and additional processing hardware onboard for processing these signals.
To describe each type of tracking device better, lets start by stating that a device that simply contains a GPS chipset does not make it a tracking device. The GPS chipset only allows the device to determining it's location on the globe. The GPS satellite's transmit a fixed frequency signal, and the tracking device can measure the offset between multiple satellites signals to determine the distance the device is from each satellite and therefore correlate it's position on the globe. The next step is what differentiates what type of tracking device it is. Now what the device does with this position information is what differentiates between a satellite, GSM, and standalone tracker.
- A satellite tracker will then take this information and transmit it through a communications satellite network such as Iridium, Inmarsat, Thuraya, or Globastar to then be delivered via IP to a datacenter for realtime processing.
- A GSM tracker will send the information immediately as well by transmitting this information across land to a GSM basestation.
- The standalone tracker is the simplest, and takes this position information and stores it in onboard memory which will have to be physically retrieved to download the tracking information.
As technology continues to develop there are hybrid options of all three of these tracking devices as well. For example, there are GSM trackers that also have a satellite modem for global coverage where GSM is not available, but use GSM when available for lower operational costs. There are satellite and GSM trackers that operate as standalone trackers when there is no signal by storing the location information for transmission when there is good signal coverage. Also, some standalone trackers have some variety of radios built in like WiFi, Bluetooth, Zigbee, ANT, etc that have designated "download points" so when they return to a location like the home office, they download their data locally without physically retrieving the device. Each of the devices can seem quite similar but they are very different, so picking the right satellite, GSM, or standalone tracker is key success of your project.