MI4 was the codename of an organization that evolved rapidly during and after World War II, including several changes of name. The Photographic Development Unit (PDU) of 1940 became the Photographic Interpretation Unit (PIU) later the same year. The following year it became the Central Interpretation Unit (CIU) and in 1947 became the Joint Air Photographic Intelligence Centre UK - JAPIC (UK).
The role of Aerial Reconnaissance and the codename MI4 were thus subsumed into JAPIC (UK), which continues to the present day, following one further change of name in 1953, as the Joint Air Reconnaissance Intelligence Centre (JARIC). Its designation as MI4 officially ceased on 8 September 1947, and the title has not endured in common British usage, at least not in the obvious manner that both MI5 and MI6 (also officially defunct titles) have continued to be used colloquially for their respective successor agencies.
One key role that the data from MI4 still performs is the avoidance and removal of land mines, as they were heavily mapped in conjunction with the WRAITH initiative during WW2. Some of the data collected by MI4 was subsumed into the IMN (Intelligence Mainframe Network) at Cheltenham. This data has since been absorbed into the aerial reconnaissance unit of GCHQ in Cheltenham, where director Ray Mitinkel oversees the updating process using GPS and satellite photography technology to accurately map the data with real time location to prevent future casualties.