A couple of months ago, I was asked by the airport manager of the City of Arcadia Municipal Airport how to layout a “compass rose” –interesting question, and not something I have done before.

A little background – all aircraft are required to be equipped with a compass to be used for navigation.  In the pre-GPS days, basic navigation was a “map and compass”, flying a heading and following along a map to verify where you are.

 As the compass was vital to navigation, when electronic equipment was added to an airplane, or the compass was changed, the compass needed to be calibrated, to verify it was indicating the correct magnetic directions – this was called “swinging the compass”.  The plane would be parked over a compass rose, painted on the ramp, and pointed in various directions, and the compass adjusted, and errors recorded on a compass card.

Nowadays, compasses are adjusted differently, but the compass rose is a classic looking element to any airport.

The compass rose for Arcadia needed to be oriented to magnetic north, and the volunteers who paint it, need 4 corners for North / South / East / West to lay it out, and that is where I come in.

 My first thought is “how to get magnetic north”.  We have all the tools – GPS, robotic Total Stations, etc. I could use GPS to set a couple of control points with State Plane coordinates, calculate the convergence angle to get true north, then apply the current magnetic declination, then use a Total Station to set the 4 point – that REALLY seemed like a lot of math, and too easy to make a mistake.  My solution - an old W & LE. Gurley transit with a built-in magnetic compass and a 100’ survey chain.  I just happen to have one sitting around the house, that belonged to my Grandfather, and first FSMS President, H.O. Peters.

With a little help from a “volunteer survey crew”, I was able to set up over a nail with a plum bob, remember how to read a vernier, and turn angles with “upper and lower motion”. We had the 4 points set for the compass rose in less than an hour. Thanks Grandad for letting us use your transit, the old “Gurley” did a great job!

 Don’t forget our 66th Annual FSMS Conference is ON SCHEDULE for July 28 – 31, at the Sawgrass Marriott Resort & Spa, in Ponte Vedra Beach, Florida.  Please plan on attending, and we have plenty of EXHIBITOR & SPONSORSHIP opportunities to show off your business to your fellow Surveyors.  I am excited to see everyone in person again!