Also interesting are the resolution targets, using sets of black and white bars at varying widths in both X any X orientation, to determine the spatial resolution i.e. how high frequency a component could still be imaged separately as lines, similar to TV test cards. These are discussed in various blogs [1][2] with some amazing picures. I think these were for both satellite imaging and spy-plane (U2 and SR-71 plus less exotic surveillance systems) and not just the USA. This article [3] shows some satellite test targets in the Gobi desert, presumable for Chinese (PRC) spy satellites, and also has a cool picture of the world's largest compass rose, at Edwards dry lake bed, as well as explaining the crosses from the original article, and talking about radar altimeter targets (another dry-lake bed) that are mapped to centimetre accuracy in altitude for calibrating GPS and other systems.<p>I find it a really interesting area of industrial/scientific archaeology, with some fascinating stories.<p>[1] <a href="http://www.clui.org/newsletter/winter-2013/photo-calibration-targets" rel="nofollow">http://www.clui.org/newsletter/winter-2013/photo-calibration...</a>
[2] <a href="http://www.bldgblog.com/2013/02/optical-calibration-targets/" rel="nofollow">http://www.bldgblog.com/2013/02/optical-calibration-targets/</a>
[3] <a href="http://www.atlasobscura.com/articles/landscapes-made-for-satellite-eyes-calibration-targets-resolution-tests-and-giant-desert-compasses" rel="nofollow">http://www.atlasobscura.com/articles/landscapes-made-for-sat...</a>