The Merton Oblique And Tactical Photo Recon

In the Missions Remembered book there is a description of a mission by Maj Joe Thompson Jr., flying a photo recon P-51.

The Merton Oblique was a technique that involved using aerial recon photos that had been taken in a particular manner and overlaying a grid on them that could be used to aim artillery The accuracy of the method was such that it eliminated the need for ranging shots and enabled shells to hit the target right off. This worked so well that the Germans thought the US Army had figured out how to use radar guidance for the rounds.

Maj Thompson was pulled off flying for a while because he had flown so many missions. But a request came though for him to fly a mission near Mecinich to support our troops advancing that area and his mission was approved.

They flew the mission, diving from 12,000 ft to the required photo altitude of 3000 ft - a perfect altitude to encounter light flak, with his wingman calling out flak if he saw it. At the end of the run normal procedure would have been to pull up to the Left. But a little voice in his head said, "Don't go Left, Go Right." So he pulled up to the Right and flak exploded where he would have been had he gone Left.

I'v never heard of the Merton Oblique before.

Merton Gridded Obliques were a British invention. Was based off British WW1 experiences in directing artillery late in WW1, utilising large scale gridded trench-maps that were drawn from information provided off aerial photography. In particular, in late WW1 the cartographers were having difficulty in keeping up with the production of the trench-maps, so someone had the brilliant idea of overlaying the grid and the useful cartographic information directly onto a mosaic of photos, which in turn was photographed and printed in a large size on a large scale.

RAF Army Co-operation Command and British Army Artillery officers renewed a form of this at the outbreak of WW2 and used it in a form during the Phoney War and then the Battle of France in 1939-1940. Recognising the need for system that was suited to the more rapid and fluid warfare of WW2, and that aerial direction of artillery and tactical reconnaissance in support of the Army would be conducted by aircraft with higher speed performance operating at low altitudes, a new system was required.

In early 1941, Major John Merton, Royal Artillery, at the School of Artillery at Larkhill Garrison on the south east edge of the Salisbury Plain, which was right next to the RAF School of Army Co-operation at Old Sarum on Salisbury Plain came up with the Merton Grid system and methodology for its use. It was rapidly widely adopted by the RAF and British Army, its use, including how to obtain the required photography was a required component of the Army Co-operation/Tactical Reconnaissance course for RAF pilots at No.41 Operational Training Unit, also at Old Sarum.

When the US entered the war, and in a covert way some time before hand, representatives of the US Army and USAAC/USAAF visited the UK and were brought up to date with various tactics, equipment and methods being used by the UK Armed Forces. A number of representatives of USA and USAAC/USAAF visited the Schools and the operational units and were thus introduced to the Merton Grid and other items used by the UK. Some things they chose to adopt, some they did not, some they adapted to their own procedures and equipment. The Mobile Film Processing Units attached to the RAF Tactical Reconnaissance units had the necessary overlays to be used to produce the grid patterns onto the reconnaissance photography to meet the Army requirements.

Merton Gridded Oblique.

And again HM armed forces are schooling the colonists on modern warfare.