Fleet Monitor is a Google Earth KML generator for Marine Companies to monitor their worldwide fleet position status. On the vessel side, a userland script read vessel location from gpsd, then upload that location to Google AppEngine for temporary storage. A script on end user's machine can fetch vessel's location from Google AppEngine, then generate a KML file for display in Google Earth.

There are many similar products available, some are paid, some are free, but with noticeable delay from days to weeks. The Fleet Monitor is a proof of concept that better fleet monitoring can be achieved by combine free or opensource software / service.

This software (Fleet Monitor) is released under the terms and conditions of the BSD License, a copy of which is include in the file COPYRIGHT.

The communications between vessel/google earth user and Google AppEngine is protected by 128bit AES encryption.

Public Key is used to exchange the random generated AES key. The peers have each other’s Public Key.

The gps data of vessel is upload to Google AppEngine before it can be fetched by end users (Google Earth). To ensure confidentiality and data integrity, those gps data is encrypted with another set of AES key which only share between the Google Earth User and the vessel. Vessel A will NOT know Vessel B’s location because it does have the AES key use between Vessel B and end user. Again, Public Key is used to exchange the AES key.

A XML file contains vessels locations is generated periodically on the end user’s computer after receive & decrypt the gps data. Google Earth reads and displays the placemarks in this XML file.

format of gps data package

• 4 byte signed integer lon x 1,000,000
• 4 byte signed integer lat x 1,000,000
• 2 byte signed integer heading in degree
• 4 byte unsigned speed in knots x 1,000
• 4 byte unsigned time of gps reading
• 4 byte unsigned time of message generated

The total size is 22 byte, after 2 layers of encryption, the final data package is 132 byte long for a vessel during test. When upload every 10 minutes, the bandwidth used is 19Kbyte a day, exclude the HTTP overhead.

Fleet Monitor is written and tested on Python 2.7, there isn't much advanced python technique involved so it is possible to run on lower version of Python.

It does require PyCrypto >= 2.3 in order to import Public / Private key in ascii format. Fortuanately, Google AppEngine already support it.

Google App Engine SDK is required to upload the software to AppEngine.

There are three parts.

The vessel should has a computer with gpsd installed and work properly. PyCrypto >= 2.3 should be installed. Run the rsa_keygen.py to generate a pair of public/private rsa key. Save the private key under the same directory of reporter.py, the public key should go to gapp directory which will upload to Google AppEngine.

Run rsa_keygen.py again to generate another key pair for the part runs on AppEngine. The public key should be distributed to every peers, including the vessel and the end user.

run path_to_app_engine_sdk/appcfg update path_to_localpart upload it to App Engine.

Please refer to App Engine's Document for detail.

Download and install python and pycryto. Run rsa_keygen.py, save the public key to gapp directory.

All config options are in peers.conf, hope that file is self-explantory.

If you have any comments, corrections, or improvements, please post to gpsd's mailing list, or contact Chen Wei<weichen302@gmx.com>.