photocontrol
/ˌfəʊtəʊkənˈtrəʊl/noun
1Control by means of light.
2 Surveying. (Frequently in form photo control.) A system of precisely surveyed reference points (in terms of which subordinate local surveys are carried out) consisting of points that can be identified on aerial photographs; the establishment or availability of such a system of points.
Origin
1950s; earliest use found in The Botanical Gazette. From photo- + control.