Though it is called a camp on the map, it is actually an Iron Age boundary dyke or an unfinished hillfort, depending on who you listen to. From the aerial photo on multimap I must admit that the latter seems more likely. There is also evidence in the link posted by wideford that further justifies this conclusion (Evidence of post-holes for example)
I have seen it from the road, or from Caburn just to the east, for years, but never visited it. I plan to remedy that soon...
ArchSearch actually gives two Iron Age hillforts as Ranscombe Camp , only with a 4-figure grid reference that gives a km latitude ( TQ4309 sic ) . These are EHNMR-626257 excavated in 1878 and EHNMR-626966 in 1959-60 . http://www.yeoldesussexpages.co.uk/history/historic.htm gives us a probable stock enclosure !