RELATIVE GPS

Relative GPS is a project aimed at providing high-precision, relative tracking information for a scalable network of mobile GPS receivers. It is based on the algorithms and methodology described in the paper High Accuracy Differential Tracking of Low-Cost GPS Receivers by Hedgecock et al.

The project is implemented as a Java-based library and is not intended to be used as a standalone application. See the Installation and Usage sections for more information on how to set up this library for inclusion in your own project.

If you plan to distribute derivative or standalone works which include any part of the source code provided here, please refer to the LICENSE document for additional information.

Installation

Installation of this library is as simple as downloading a copy of the code and including it in the source tree for your own project. For example in Eclipse, you would Import this directory as an existing project into your workspace. Then, in the Project References page of your project's property info, make sure that the relativegps checkbox is marked.

Note that this library also relies on a bundled library called the MessagingFramework which can be found in the libs directory. You must ensure that the project is able to find this library to avoid compile errors. Again, in Eclipse, this entails adding the MessagingFramework.jar archive to the list of libraries in the build path for this project.

Usage

In order to use this framework, you will need to define three separate interface modules:

1. A SerialInterface which will be used to provide GPS data packets in the UBX format to the framework,
2. A NetworkInterface which will be used to broadcast and receive byte streams over a network, and
3. An OutputInterface which will be used to handle the tracking outputs produced by the framework.

Each Interface you provide will need to extend the RLInterfaceImplementation class and override the following three methods:

• void openInterface() which will provide any code necessary to open/initialize your interface,
• void closeInterface() which will provide any code necessary to gracefully close/shutdown your interface, and
• void handleMessageFromFramework(final RLMessage message) which will handle any messages you may receive from the framework.

Currently, the SerialInterface will never receive any messages that must be handled, the NetworkInterface may receive a ByteStream message that must be broadcast to the entire network, and the OutputInterface may receive a Result message containing the relative tracking results for the current epoch from the framework. Additionally, the SerialInterface will need to provide a ByteStream message containing a byte array of the raw UBX packet to the framework by calling sendMessageToFramework(new RLMessage(new ByteStream(dataPacket)), false), where dataPacket is a byte[], and the NetworkInterface will need to pass any network packets it receives to the framework by calling sendMessageToFramework(new RLMessage(new ByteStream(packetData))), where packetData is a byte[] containing the received packet.

Once your interfaces are all created, you can set up the entire framework by calling the following functions:

• RegLocFramework framework = new RegLocFramework([Your Receiver ID Here]);
• framework.connectInterfaceToImplementation("NetworkInterface", new [Your NetworkInterface Here]);
• framework.connectInterfaceToImplementation("SerialInterface", new [Your SerialInterface Here]);
• framework.connectInterfaceToImplementation("OutputInterface", new [Your OutputInterface Here]);

Then, to start the framework, you simply call framework.startProcessing(). Likewise, to stop the framework, you can call framework.stopProcessing().

Web Site

For the most up-to-date information regarding the techniques and methodology used in this library implementation, please visit the Relative GPS Project Web Site.

Notice

Relative GPS contains source code that is Copyright (C) 2014 Will Hedgecock. It is distributed under the GNU Affero GPL license. Refer to the LICENSE document for more information about using this library in your own project.