Compass Rose

[brianreid]

I have installed a new magnetic compass. Now it needs compensation and a compass card. To do this I need an accurate compass rose. Unfortunately, I can't find any listing of airports with roses. I've looked in one AFD that I have but there is no listing in the back like there is for VOR check points. I have also looked at specific airports that I think had a compass rose a decade ago but the AFD doesn't indicate a current rose if it ever did. I even tried Google.

So... how can one find a compass rose?

 

[mmarien]

You can probably make up one yourself with a 100 metre rope, a WAAS handheld GPS and a little trig. WAAS accuracy is about a metre. One metre in 100 is about a half a degree: atan (1/100). Is that accurate enough for the compass calibration?

Paint a start point. Anywhere north and south will have the same longitude. East and west will have the same latitude. These are true directions. Use the published magnetic declination for your area to calculate an offset using the formula: tan (declination) x 100. Measure that distance (in metres) off the ends of your 100 metre lines and join the points to paint a magnetic compass rose or more like and X. There is going to be some error because of the accuracy of the WAAS GPS and the crude equipment. That will give you and your helper something to argue about over beers.

If you know of a surveyor, he'll probably do it more accurately for a ride in your airplane. 

 

[brianreid]

Thanks but I have found a local airport that already has a rose laid out. I am still curious why there is no listing anywhere of airports that have a rose. A magnetic compass is required equipment for all aircraft. Without calibration it's basically useless.