Calibration Targets 2: Edwards Air Force Base

A few weeks ago we had a look at some calibration targets used by the classified Corona spy satellites. Today we are looking at a set of calibration targets and other interesting features at Edwards Air Force Base, California.

We start with one of the most obvious features at the site: The largest compass rose in the world. According to Atlas Obscura its purpose is to help with emergency landings. It was created in the 1930’s long before satellites existed and was designated a National Historic Landmark in 1985.

The compass rose points to Magnetic North.

There are several emergency runways painted on the lake bed, and there are also a couple of very large rulers:

(1) A ruler with markings at each quarter mile. (2) Another ruler with numbered markings at each mile.

(1) Another part of the ruler with quarter mile markers. (2) and (3) Markers used for calibration.

There is also a long row of special calibration markers spread out over 18 miles:

Most of the calibration markers are rectangles containing sets of three white bars in different sizes. This one also features three large squares with three different shades of grey:

Many of the markers have old aircraft or vehicles near by. Presumably used for testing how well the satellite or aircraft camera can identify them.

This marker also has a bullseye

An aircraft, helicopter, pressurised tank and other structures probably also used for testing imaging.

A variety of interesting aircraft on show near one of the entrances to the base.

More aircraft on show at one of the entrances.

Be sure to explore the whole base in Google Earth as there is a lot more to see! We have marked some of the interesting stuff we found in this KML file

About Timothy Whitehead

Timothy has been using Google Earth since 2004 when it was still called Keyhole before it was renamed Google Earth in 2005 and has been a huge fan ever since. He is a programmer working for Red Wing Aerobatx and lives in Cape Town, South Africa.


  1. Chris Kennedy says:

    The third from last photo probably shows the fire/rescue training area. Airport fire departments used to use old aircraft for fire training, but they quickly burned up and had to be replaced. Now they tend to use structures like the one in the photo at this URL, which are purpose-built.

  2. Kengrok says:

    There’s a place in China where you can calibrate your satellite cameras, 40°51’6.10″N 109°37’45.90″E, in case you’re worried about moire patterns, white balance, and that sort of thing.

  3. In your KMZ there’s a placemark called “What are these runways? Drones perhaps?”. They don’t look like runways at all. They are probably hardened storage bunkers for munitions and fuel and those are just access roads.

    • Timothy Whitehead says:

      Thanks for the input. I wasn’t sure what they were and didn’t have the time to research them.

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