and origins make the conversion non-trivial. Conversion of Cassini Grid references is of interest to modern archaeologists attempting to locate wartime sites and artefacts. See also Military Grid Reference System External links Where's the path, An app that allows different grids to be displayed side by side for cross-referencing, including modern Ordnance Survey and 1930s OS using the Cassini grid. References Further reading J. Penny, "Straight to the point right on time", Regional Historian, vol. 5, pp. 11–15, 2000. Penny gives a formula for converting Cassini Grid to National Grid references. Geography of the United Kingdom Maps from Ordnance Survey Geographic coordinate systems Military maps