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Author Topic: XML datafeed  (Read 6713 times)

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palmar

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XML datafeed
« on: June 28, 2007, 10:49:56 am »
I understand the (delayed) datafeed on port 7879 is similar to the port 30003 output of SBS-1, i.e. it is sending out messages as they were received, but the stream is formatted in XML? Or is this a clocked dump of database data, i.e. not as the messages are received, but let's say a complete dump of all flight data every x seconds?

I have serious doubts that this an efficient way of coding the data. In the London TMA there are up to 2-300 flights transmitting at the same time and XML tags would represent a huge overhead for the data stream. Indeed, for me XML is the most unefficient formatting tool for streaming data.
 
Any comments?
Is there a data format description available for the XML feed?
Can that be made available here?
Thank you for clarification

AirNav Support

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Re: XML datafeed
« Reply #1 on: June 29, 2007, 03:14:12 pm »
Sorry for the delay in getting back to you. I have passed this on to software development and they should get back to you soon.

AirNav Development

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Re: XML datafeed
« Reply #2 on: June 29, 2007, 03:42:41 pm »
Hi

Thanks for your interest in AirNav RadarBox.

The feed works the following way:

1- Flight messages are received in real-time from the decoder.

2- Selected/relevant messages are added to a queue with a an attached time stamp. Not all messages are added because many of them them are irrelevant (imagine you have a flight being tracked with all the information available: aircraft type, lat/long, altitude - if a message containing only the Mode-s hex code of the aircraft is received it is not added to the queue as it adds no info to what the software already has all the information regarding that flight). If for example a change in altitude or V/S is received the message will, of course, be added to the queue.

3- There is a timer permanently checking the queue for messages older than 4 minutes 59 seconds. If there are messages in this condition, they are deleted from the queue and added to the output port.

We used XML for easy compatibility with all possible programs (XML is the world reference in data exchange).

Format as below:

<MODESMESSAGE>
   <DATETIME>20070622141943</DATETIME>
   <MODES>400F2B</MODES>
   <CALLSIGN>BAW134</CALLSIGN>
   <ALTITUDE>120300</ALTITUDE>
   <GROUNDSPEED>451</GROUNDSPEED>
   <TRACK>234</TRACK>
   <VRATE>0</VRATE>
   <AIRSPEED></AIRSPEED>
   <LATITUDE>-14.1102</LATITUDE>
   <LONGITUDE>-31.5789</LONGITUDE>
</MODESMESSAGE>


Hope this clarifies it. Any question reply to this forum or drop us an email.
Hope you enjoy RadarBox!

palmar

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Re: XML datafeed
« Reply #3 on: June 29, 2007, 05:21:45 pm »
Thank you for your answer, that clarifies a bit.

More questions:

Is the entire dataset output or only the parameter that has changed. From your example I would assume that the entire dataset is output, as callsign and other parameters cannot appear in one Mode-S message.

Quote
XML is the world reference in data exchange

Yes, but that's more for static data exchange and you are streaming data here. Se from your example, the overhead is more than 200% of the flight data, this is what I am concerned of.

Anyhow, any further information is welcome as applications that are written for SBS port 30003 may be well adopted for Radarbox port 7879.

palmar


AirNav Support

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Re: XML datafeed
« Reply #4 on: June 29, 2007, 06:41:02 pm »
Regarding the data exchange:

There is a 3rd party application which does the same as SBSplotter which is ready to release soon for RadarBox. http://www.akzah.com/blog/

He has been using RadarBox in London and at peak periods he gets 500 of the modes xml messages every 10-15 minutes send via the socket.

He says this is nowhere enough to flood any application and the xml just makes its easier to grab the data out of the message rather than using a comma delimited message.