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Subsystem VFR backend

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rueckwaertsflieger edited this page Jun 20, 2017 · 9 revisions

VFR-B Virtual Flight Radar Backend

The Virtual Flight Radar Backend is a core software subsystem for transcoding data feeds and computing additional data. From the start, transcoding and merging of Flarm and an ADS-B objects for display in XCSoar has been realized.

VFR-B Basic

The basic backend provides all the functionalitiy for displaying radar targets' positions and height with XCSoar and wind read from a remote sensor. The first beta arrived at 1st of May 2016. The second release occured on 4th, April 2017. The latest release 2.1.0 occured on June, 20th 2017. All known bugs (or non-features) from other software, necessary for the AMVR functionality are addressed. Further, all secondary application's requirements are realized. As such, VFR-B now is enabled to support even mobile application, say, act as in-flight Flarm and ADS-B receiver with outstanding reception compared to original Flarm devices.

Features

  • Read SBS messages from SDR ADS-B receiver, typically on TCP port 30003.
  • Read APRS messages from APRSC server and SDR OGN/Flarm receiver respectively, typically on TCP port 14580.
  • Read SBS and APRS messages from remote receivers and central servers.
  • Read absolute atmospheric pressure from sensor or remote weather station.
  • Shifting ADS-B pressure height concerning live atmospheric pressure in order to correlate GPS height and pressure altitudes.
  • Filtering duplicate position reports in case of target is broadcasting via both, transponder and Flarm.
  • Creating Flarm NMEA sentences $PFLAU and $PFLAA for output to XCSoar via TCP port.
  • Reading GPS height from live GPS reception.
  • Creating GPS sentence $GPRMC from static position or live reception.
  • Creating Flarm sentences $PFLAA and PFLAU for every radar terget received
  • Reading wind data from a remote Sensor.

VFR-B Pro

Expected in spring 2018, the pro backend system will provide additional functionality for estimating the POA - Probability Of Arrival - of flight targets surrounding the airfield. The POA follows three criteria for estimating the time, an aircraft approaching probably will need to reach at the airfield.

The POA is based on the three following criteria:

  • Course will intersect with a cylinder around the airfield's position, Course Of Arrival: COA
  • The Height Of Arrival HOA will be lower than the top of the cylinder around the airfield's reference point.
  • Time Of Arrival TOA within the airfield cylinder is expected in less than 120 / 60 / 20 / 10 sec.

Thus, the proximity to the airfield is expressed in time needed to enter the airfield's sector. As a visualization the elements from known warning levels of a Flarm based collision warning in XCSoar are used.

Features

  • Interpolation of target courses expected, when reception lacks temporarily.
  • Computing missing values in radar reception position reports: track, speed over ground, vertical rate.
  • Computing the three values COA, HOA, and TOA.
  • Generating warning levels corresponding to time to TOA less than given thresholds.

The VFR-B is hosted on GitHub https://github.com/Jarthianur/VFR-Backend

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