Log File Position Source (C++)¶
The Logfile Position Source shows how to create and work with a custom NMEA position source, for platforms without GPS.
The data is read from a file which has positional data in NMEA format. The resulting time and position information is then displayed to the screen as simple text in date/time and latitude/longitude format.
This example class reads position data from a text file, log.txt . The file specifies position data using a simple text format: it contains one position update per line, where each line contains a date/time, a latitude and a longitude, separated by spaces. The date/time is in ISO 8601 format and the latitude and longitude are in degrees decimal format. Here is an excerpt from log.txt :2009-08-24T22:25:01 -27.576082 153.092415 2009-08-24T22:25:02 -27.576223 153.092530 2009-08-24T22:25:03 -27.576364 153.092648
The class reads this data and distributes it via the
Here is the definition of the
The main methods overrided by the subclass are:
startUpdates(): called by client applications to start regular position updates.
stopUpdates(): called by client applications to stop regular position updates.
requestUpdate(): called by client applications to request a single update, with a specified timeout.
When a position update is available, the subclass emits the
Here are the key methods in the class implementation:
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