bjwoody61

Tracking Accuracy

9 posts in this topic

How accurate is tracking of my position on the map. Seems to me that my position on the map is off quite a bit. When following my flight plan using GPS sometimes I am told that I am off course. The correction given will put me on the flight path displayed on the map but will be off on the GPS. Also, taxing around the airports will be off a lot.

I have checked GPS coordinates between FSX and Google Earth and surprisingly they are really close. Why the discrepancy

 

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There is always the possibility of being a little off between the SIM display, which includes the GPS and Scenery and the Map display.  This could be caused by something as simple as the AIRAC data not being exactly the same version or a difference in the SIM scenery and the real-world scenery.  You can avoid the "off course" calls by increasing the Allowed Course Deviation on the ATC Settings page. 

When trying to follow a taxi route, the difference is more likely to be off by a wider margin because the taxi route is defined from taxi data that is way out of date and so there may be larger variance. 

Dave

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6 minutes ago, Dave-Pilot2ATC said:

When trying to follow a taxi route, the difference is more likely to be off by a wider margin because the taxi route is defined from taxi data that is way out of date and so there may be larger variance. 

I don't understand taxi data being out of date. Is this defined in FSX airport BGL files. I have some updated airport add-on files. Does P2A not take those into account. Does the taxi manager have a say in this or am I barking up the wrong tree?

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The taxi data is not read from your bgl files.  That is why it is out of date vs. the scenery. 

Enabling reading from the bgl files using MakeRunways is on the future enhancements list, but not there yet.

Dave

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Can't the gps coordinates be sent to the map for tracking using gpsout in fsuipc even while taxing?

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Of course.  That's how it works.

If you pull up the Satellite image and taxi around, then the Aircraft in P2A is usually right where it would be in the real world.  If it's off, it's  due to the scenery in the SIM being off, so the taxiing being done in the SIM world is not aligned with the real world represented by the map. 

This has nothing to do with the data used for building taxi instructions, which is what I was referring to above as not coming from the bgl file at present.

 

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ok. I will do some more testing to see if there is a difference between FSX and Google Earth (real world). My previous test was on a few key points and they were pretty much dead on between the two. Will get back with you on the results.

 

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Testing done. I opened the KSEA bgl file and compared the intersection points with Google Earth. They were all really close.

Come to find out that this was a bgl from Air India Group and they used Google Earth as reference when building this file. so, yeah, it would be pretty much dead on.

I also found that with the different gps mapping programs out there do not match! It depends upon what reference they are using. Example being with Google Maps and Google Earth can have a difference in coordinates for the same position as much as 30 meters. So if you are using Google Earth to build BGL airport files and using Google Maps to display those points one can have a fairly large variance in position.

I don't know why I hadn't thought of this before with my past experience with a real Garmen. Any address entered into its mapping system could be off as much as 200 feet.  My bad!! 

Thanks for your patience and all your work

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