Overview of GPS tracking system technologies

Question

Background: I've been asked by a friend to estimate the cost of setting up a GPS tracking system for a small fleet of buses, so we can do real time reporting of bus locations via a webmap.

In my research, I saw three kinds of active GPS trackers:

1. Radio
2. SMS
3. Satellite

Some major considerations are

1. minimizing long term costs, and
2. making the system as reliable as reasonably possible.

Secondary concerns are minimizing up front cost, latency, difficulty of installation/setup, level of support required after the initial setup is complete.

The buses run within a 5 mile radius, so radio is feasible.

With an eye towards reducing long term costs, radio seems good: it would be the only way to run the system without a middleman.

SMS requires cell phone towers, and satellites require a space program. I am concerned that a DIY solution with radios might prove to be less reliable, though.

But if we bought SMS transmitters that provided the data through a third party API, they could go out of business, or have unacceptable down time or latency.

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My question(s):

• What would each of these three solutions look like?
• What hardware is involved?
• What are the trade-offs between them?
• What problems have you encountered?
• Have you used a system that Just Works?

Answer 1

I can't help with understanding a a vhf/uhf radio tracking system - no hands on experience. But I can help regarding satellite / mobile systems.

Looks like you omitted one important option - mobile data via gprs GPRS technology or other IP based technologies. SMS may not be a good option since the cost of high volumes of SMS messages can be prohibitive and sometimes SMS messages are queued and delayed more than may be acceptable (at least they are where I am).

Our system receives data from GPRS / 3G IP connections and also via satellite downlink using the Globalstar, InMarSat and Iridium satellite constellations.

GPRS systems typically send their position reports to a server that you would operate via an IP connection. Satellite systems typically provide position reports by allowing your server to periodically query their gateway for new reports.

There are more questions you need to consider:

• How frequently do you require reports from the buses? A mobile based system can normally send reports more frequently than sat systems but at (depending on available plans) a greater cost. I think you'll find that most satellite trackers are intended to send at periods of 5+ minutes and sometimes more.
• Does it matter if the buses can't send a report because they move into a mobile dead area or an area of poor satellite connectivity?
• How reliable does the system need to be? Some satellite systems are more reliable than others. At least one sat system can introduce lengthy delays into reports due to the architecture of their system.

A typical architecture for your proposed system would include one or more servers and software for user terminals (computers) that can fetch data from the server and display it as required.

The server(s) would:

• Receive data from trackers and/or Poll an external gateway for data

• Translate the received data into a usable format.

• Do some lookups or calculations based on the received data

• Store the translated data into a data base

• Periodically extract info from the database and store it into some files that are useful for clients (XML, JSON, CDF, whatever)/
• Serve user requests via a web server ( or by some other technology)

Have a look at the Axxon SmartOne tracker (Very reliable industrial grade sat tracker) (Globalstar satellite network), the Spot tracker (a consumer grade device and Spot's own visualisation web based software), and some of the software packages that run on mobile phones (some of the available packages let you specify any server as the data destination, others force you to use a single vendors proprietary system :-( We've done trials with many of the inexpensive pocket trackers available from China but we've found them either too unreliable or too limited.