Why do I get requests from far away?

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Why do I get requests from far away?

Postby roslewski on Mon Apr 02, 2012 6:14 pm

I am one of the pilots here, and I love having the auto-emailed requests for transport. However, I don't think it's working right, or I have something set wrong in my profile that I can't find. I am in Dayton, OH, and routinely get auto-emailed notifications of transports that don't come anywhere near Dayton. I know about the setting under my profile of "distance I'm willing to travel one-way", and I keep adjusting it to see if that helps, but it doesn't seem to. Currently it's set at 75nm (which I'm certainly willing to fly farther than, but I was trying to see if it made a difference).

Today I got one notification for Birmingham, AL to South Burlington, VT, for which a direct line between the two, comes at the closest 141 nm away from me. And this is fairly normal. A week or so ago I got one for Nebraska to somewhere in California, I think, so the complete opposite way!

Is there something I'm missing in the profile settings, or does the automated e-mail function just not work very well?

Thanks,
Russ
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Re: Why do I get requests from far away?

Postby Steve Foley on Fri Apr 06, 2012 12:53 pm

Its the way the calculation is done. Assuming you use 75 miles, the system will notify you if diverting to your airpoprt would increase the length of the trip by 75 miles or less.

I use a formula that can calculate the distance betweentwo lat/lon pair, so I calculae the length of the trip (d1), and calculate the trip length using your airport as a stopping point (d2) and (d3). If d1 + 75 is less than d2 + d3, you get an email.

If someone can come up with a formula to find the distance to a courseline from a particular airport using php functions, I can incorporate it into the program.
The best way to contact me is via email:

steve dot foley at gmail dot com
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Re: Why do I get requests from far away?

Postby roslewski on Fri Apr 06, 2012 5:04 pm

Interesting, thanks for the response! I had no idea what was going in to the calculations.

I don't know what formula went into it, but the FAA has an Excel calculator to do basically what you want at

http://www.faa.gov/about/office_org/hea ... rps_tools/

use the "Ellipsoidal Calculator Spreadsheet".

The "Three Points" tab would return the desired values: A = the origin airport, B = destination, C = your airport, and it will return "y" which is the distance to courseline. This is one of the calculators used to assist in instrument approach procedure design, so it should be accurate.

Unfortunately, the spreadsheet is password-protected. Maybe the contact information at their main page, http://www.faa.gov/about/office_org/hea ... 00/afs420/

will help get you the formula that goes into it.

I know nothing about php or even if it's implementable from this Excel formula, but figured I'd offer that suggestion.
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