Adding a Telemetry Translator to AUV Workbench

This is an advanced task for AUV Workbench developers.

Writing an importer that reads a robot telemetry file into AUVWorkbench generally involves reading a text file and then translating it into XML using Autonomous Vehicle Command Language (AVCL).

• Subclass the abstract class TelemetryFileTranslator in the package avcl.translate
• Create constructors for the importer class that take an input filename
• Write a method called getDefaultAvclDocument(). This method should create the overall skeleton of the AVCL document in an appropriate way, for example by creating an AVCL file for a surface vehicle, underwater vehicle, air vehicle, etc.
• Write a method to parse the contents of the telemetry file

The AVCL format is defined via JAXB, and JAXB 2.0 documents can be created manually by using the ObjectFactory class. The general strategy for creating an AVCL document is to manually create the top level document and all its elements by making calls to ObjectFactory. For example:

factory = new ObjectFactory();
defaultAvcl = factory.createAVCL();
defaultAvcl.setVersion("2.0");
AvclHeadType avclHead = factory.createAvclHeadType();
defaultAvcl.setHead(avclHead);

This is very similar to building a DOM tree; create an element, and add it to its parent.

The TelemetryFileTranslator abstract contains the basic structure for creating a resulting AVCL file from a text file. It implements the TelemetryTranslatorInterface, which defines the overall methods for creating an AVCL file from telemetry. The TelemetryTranslatorInterface is there in case we need to create an AVCL file from some other source, for example from network-based events rather than a file. The TelemetryTranslatorInterface is largely redundant at this point since our only current method for importing telemetry is from a file.

The subclass of TelemetryFileTranslator you are writing should have a constructor that sets an input filename that contains the telemetry data. The constructor should call the superclass's setInputFilename() method to set this.

You should override the getDefaultAvclDocument() class, and in the implementation make a call to the superclass's method:

avclDocument = super.getDefaultAvclDocument();
getAvclDocument().setVehicleType("AMN");

In the subclass method you should set the vehicle type (underwater, air, surface, etc), add any metadata such as the name of the translator and the date of translation, and set the geo-origon for the data.

The geoOrigin is the latitude and longitude for the project. The Workbench generally uses (x,y) coordinates for telemetry position, and these (x,y) coordinates are offset from a latitude and longitude origin. This origin should be set to that of the AuvWorkbench project.

The parse() method is the heart of the import process. This reads the telemetry file and creates the corresponding AVCL elements for the telemetry. The data in telemetry files is often corrupted or wildly off base; if you're reading latitude and longitude, for example, it's not uncommmon to get zeros for both, or to have wildly off-base time hacks, or simply bogus data that does not match anything at all. Very often the telemetry data is exported from a spreadsheet, and there will be text column headers interspersed at random places in the data lines.

One thing that you must do is translate the latitude and longitude readings--the most common location format--into (x,y) positions. This is done via OpenMap libraries. This is handled by a method in the TelemetryFileTranslator superclass:

LatLonPoint location = new LatLonPoint(Float.parseFloat(latitude), Float.parseFloat(longitude));
Point2D xy = this.latLongToXY(projectGeoOriginLatLon, location);

The method takes the project geo-origin and the vehicle latitude and longitude as arguments, and then translates them into an (x,y) position.

Another thing to be alert for is very frequent or large telemetry sets. The AVCL file is kept in memory, and a large telemetry data set may exceed the RAM of a host. To alleviate this problem, you should allow the user to filter on the frequency of telemetry points.

After completing the subclass of TelemetryFileTranslator, you must modify some other files. TelemetryTranslatorGui.java in the workbench.main package should have changes made to the fileFormatStateChanged() method and vehicleNames variable. The configuration file configuration/templates/c_app.xml should be changed to include the new translator class.

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