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====== Using VOR beacons for tracking flying objects ======

[[https://en.wikipedia.org/wiki/VHF_omnidirectional_range|VOR radio bacons]] are a type of short-range radio navigation system for aircrafts, distributed evenly to cover most of the airspace. 

By observing their signal, it was found out that the signal received on ground contains clearly distinguishable reflections from flying objects - see e.g. [[http://www.astrozor.cz/graphics/upload/reports/151-05.28.14-18_28_18.jpg|VOR beacon observation]] by station [[http://www.astrozor.cz/index.php?udalost=151|in Prague]]. 

{{ :cs:vor:vor_airplanes.jpg?300 |}}

{{ :cs:vor:vor.jpg?300 |}}

Coordinates and frequencies of all existing VOR beacons can be found at webside [[http://ourairports.com/big-map.html#lat=0,lon=0,zoom=2,type=Hybrid|ourairports]] - check the navaids in map parameters.


===== Signal processing =====

VOR beacons work at carrier frequencies in range 108 - 118 HMz. Sampling of this 10 MHz wide band should make it possible to process all beacons at the same time. [[https://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast|ADS-B]] data could be used to filter out know airplanes from the signal. Rest of the objects should be pick out as suspicious and should be further identified for example using a [[https://en.wikipedia.org/wiki/FDOA|FDOA]] method.
 
Using VOR beacons to observe meteors has one advantage - these beacons work in a protected air band that is continuously monitored for interference. Therefore, the quality of obtained data is better than in other bands.

==== Hardware ====

To process and digitise signals, a [[http://www.mlab.cz/WebSVN/filedetails.php?repname=svnkaklik&path=%2Fdokumenty%2Fskolni%2Fdiplomka%2F2014-05-12KakonaDiplThesisCTU-Prague.pdf|new digitizing unit]] should be available. It would be advantageous to change an SDRX01B receiver for a newer version, dedicated to digitise signal in bandwidth approximately 10 MHz, in order to improve the parameters of the receiving chain.

==== Algorithms ====


   * [[https://hal-enac.archives-ouvertes.fr/hal-01839330v2/document|Compensation of VOR signal scattering on wind turbines]]
===== Data from ADS-B =====

To obtain reference data and to filter airplanes, ADS-B data can be used.

==== dump1090 ====



  sudo apt-get install librtlsdr-dev git
  git clone https://github.com/MalcolmRobb/dump1090.git
  cd dump1090
  make
  sudo rmmod dvb_usb_rtl28xxu


Now you can run the software e.g. with parameters to create a local web server: 
  ./dump1090 --interactive --net