In a previous post, I put together lots of images of photo resolution markers, from across the USA. This post is about the four markers found at a little known airfield named Naval Outlying Field Webster in Maryland. In posts on this subject in other blogs it is often incorrectly named Walker Field, just to make things confusing. The four markers are in a straight line, with an almost exact 2000ft between them. This is likely for some sort of calibration testing, so the planes have an exact known distance to calibrate their cameras from. They are in parallel with one of the main runways to make it easy to maintain them, and as another reference for the planes.
NOLF Webster is located 12 miles south west of Naval Air Station PAX River. It was bought by the military from a set of jesuit fathers during WW2 for just $96,000. It was bought as a auxiliary airfield for PAX River, to send aircraft to on busy days. PAX River is a very famous aircraft testing base, with lots of history associated with it. Part of the history is the photoreconnaissance training school found there. That explains the reasoning for the photo resolution markers just 12 miles to the SW.
NOLF Webster is good as an air base due to it’s great location. It has a good approach by water from two sides, especially good for testing and training. The other approaches were mainly woodland and fields. The three runways are built in accordance with the prevailing winds, with two of the runways being 5,000ft long. The base was heavily used in the 1950’s as a ‘touch and go’ site for training at PAX.
In the 1960’s the former electronics test division moved in, now known as Naval Air Navigation Electronics Project (NANEP). They helped develop many air navigation systems. They stopped the interference with operations at PAX River. They may also have been a big part on the development of the photo resolution markers found there.
Most of the images I have used are taken in 2007, but the final one (of the fourth marker) is taken in 2015, where it has a slightly different pattern. This is maybe to define markers between each of them, so the planes know the final one. There don’t seem to be any other changes according to the images found on Google Earth.
Hope you enjoyed this short post, If you enjoy stories and posts on space and electronics, take a look at some of the other posts on my blog. Thank You for reading.
A few years ago, The Center for Land Use Interpretation (CLUI) reported on the dozens of Photo calibration targets found in the USA. They are odd looking two dimensional targets with lots of lines on the of various sizes, used as part of the development of aerial photography. Mostly built in the 1950’s and 60’s as part of the US effort of the cold war.
At this point, just after the second world war, there was a huge push to get better information about the enemy. The military needed better aerial recconasance. This very problem lead to the development of the U-2 and the SR-71. As part of this, there needed to be methods of testing these planes with the big camera systems attached to them. This was before the development of digital photography, so resolution is much more difficult to test.
This is where the photo resolution markers came in. Much like an optometrist uses an eye chart, military aerial cameras used these giant markers. Defined in milspec MIL-STD-150A, they are generally 78ft x 53ft concrete or asphalt rectangles, with heavy black and white paint. The bars on it are sometimes called a tri-bar array, but they can come in all forms, such as white circles, squares, and checkered patterns.
The largest concentration of resolution targets is in the Mojave desert, around Edwards Air Force Base. This is the place most new planes were tested during this time, with the U-S, SR-71 and X-15 being just some of the planes tested there. There are a set of 15 targets over 20 miles, known as photo resolution road. There are also plenty of other resolution targets at aerial reconnaissance bases across the US, such as Travis AFB, Beaufort Marine Corps Base and Shaw Air Force Base.