[Image: Lunar topography, courtesy of the USGS].
The Unified Lunar Control Network is “a set of points on the lunar surface whose three dimensional selenodetic coordinates (latitude, longitude, and radial position) have been determined by careful measurement. Typically the points consist of very small craters.” This network forms a series of cardinal points that can then be used to orient, fix, and control our topographic understanding of the moon—in a sense, lunar variants on terrestrial coordinate systems such as the trig stations of New Zealand, “a network of control marks that serve as physical reference points.”
As it happens, there is quite a long history of temporary “lunar control networks,” most of which have simply faded into cartographic obsolescence. For instance, you can read this brief “Chronology of Lunar Control Networks.” It includes such phrases as the Apollo Zone Triangulation, the Manchester Selenodetic Control System, the Kazan Series, and the Clementine Control Network—a taxonomic graveyard of discarded geographies, these lost trigonometries of the moon.
(Thanks to Jon Rennie for pointing out trig stations to me a few weeks ago).