Eerily tranquil images taken by brave spitfire pilots sweeping the French coastline in 1944 show the German-occupied Normandy coastline just before to the D-Day landings Allies stitched together the photos to form a 20ft panorama of Normandy coast to prepare for invasion of Gold beach Images were hand annotated to show key targets and dangers to ensure the troops were fully prepared for battle The secret artefact has been unearthed by son of a senior Navy man and is to be sold at auction next week A top secret 20ft long panorama of the Normandy coastline taken during daring spy missions just months before D-Day has emerged for sale almost 70 years later. The photos were snapped by highly-skilled Spitfire pilots who recorded the landscape as seen from the sea ahead of the pivotal beach invasion. The annotated images identify key landmarks along the five-mile section of 'Gold' beach, where British troops landed on June 6, 1944 and where around 1,000 people lost their lives. Top secret: This is part of a fascinating 20ft-long panorama of the French coastline taken during daring spy missions just before D-Day, which will be sold at auction next week Vital preparations: This photograph from 1944 shows a British amphibious tank going ashore on Gold Beach on D-Day at the portion of the beach near the one above The archive is made up of 21 plates, each measuring 8ins by 11ins. When pieced together they make a panorama that is almost 20ft long. Officers studied them to familiarise themselves with the landscape and to look for where German gun emplacements were and beach exits for the soldiers. They would also have been used to create highly detailed maps and three dimensional models of the D-Day landing zones. Marked on the pictures, which cover the coastline from Arromanches-les-Bains to La Riviere, are landmarks including a tower, a lighthouse and a coastguard station. Key target: The town of Arromanche-Les-Bains was one of the key targets on June 6 1944 and this annotated images identifies its key features Incredible: Spitfire pilots and other planes and vessels used sophisticated technology at the time to plot exactly a five mile stretch of beach and surrounding hills occupied by the Germans Detail: An officer has written on this photo and highlighted the lighthouse at this point on the Normandy coast, stitched together to form part of a giant panorama Dangerous: This is the beach at Mont Fleury, home to one of the a huge gun battery that could fire on both Gold and Juno beaches, making it one of the key targets at the start of the invasion Important: St Come de Fresne, pictured here from the sea, was considered an key foothold for the Allies just east of the heart of Gold beach Plot: The Germans were completely unaware that this plotting of the landscape was taking place and it formed a key element of the June 1944 invasion Into battle: The images are being sold by the son of Captain Alexander Rodger, commander of infantry landing ship HMS Empire Crossbow (pictured) in the D-Day operation The photos were taken by brave airmen who flew just 10ft above the sea, 1,000 yards from shore and in broad daylight. They are being sold by the son of Captain Alexander Rodger, commander of infantry landing ship HMS Empire Crossbow in the D-Day operation. The ship carried two companies from the Royal Hampshire Regiment onto Gold beach, where they went on to capture their targets of Arromanches and La Hamel. Daunting: This series of pictures taken on the eve of D-Day shows how high the cliff were along Gold Beach. At points soldiers were forced to climb them, with some reaching 200ft Detail: Part of the success of D-Day was the amount of planning that had been involved. The Allies carefully plotted landmarks and buildings, like the Coast Guard here, to ensure soldiers were fully prepared when going into battle Remarkable: Spies had accurately plotted the length of Gold Beach (pictured), by putting together small photographs to make a 21ft panorama that could be viewed like a soldier coming in from the sea History: The scene and memorial at Arromanches (Gold beach), with the remains of Mulberry Harbour B a temporary harbour used by the British and Canadians to bring in troops and equipment after D-Day Captain Rodger passed the images on to his son as a keepsake following the war. At the heart of the plan on D-Day was Gold Beach and the neighbouring Omaha Beach because it was where the Allies wanted to set up temporary harbours after the invasion. This meant the Allies could land troops, vehicles and equipment on French soil without having to capture a port first. Mulberry A, as it was called, was installed at Omaha Beach, for American invasion forces; Mulberry B was set up at Arromanches (Gold Beach) for the British and Canadians. The pre-fabricated harbours were towed across the English Channel in chunks and put into place on the Normandy beaches. The Mulberry harbours were completed by May 1944 and successfully launched with the use of tug boats soon after. It allowed 220,000 men, 50,000 vehicles and 600,000 tones of supplies to be landed in France and undoubtedly helped win the war. The photographs are tipped to fetch £400 when they go under the hammer. Ian Carter, curator of the photographic archive at the Imperial War Museum, said the spy photos were commissioned by the Inter-Services Topographic Department, a joint intelligence organisation, and taken in March 1944. Mr Carter said: 'In the run-up to D-Day the ISTD used reconnaissance photos such as these along with other sources of information to build up a complete picture of the area. Highly-skilled pilots would fly very low level missions in Spitfires, Mosquitos or F5 Lightning planes to get the photos needed. They were very dangerous sorties. The pilots not only faced the possibility of attack from German planes and flak from ground troops but also the inherent dangers of flying 10ft above the waves. The planes had cameras mounted in the noses and it was vital the pilots got pictures of every inch of coastline. To avoid arousing suspicion among the Germans as to where the landings were going to take place, photos were taken of the coastline from Normandy right up to Belgium and Holland. These particular photos show the Gold area from Arromanches-Les-Bains to La Riviere. As well as highlighting primary landmarks, the images would have been used to identify the location of German emplacements and possible beach exits. They would have been seen by only the highest ranking officials and from them highly detailed maps and 3D models were drawn out and handed to officers. These photographs formed a very significant part of this historic mission. The images are being sold by London-based Charles Miller auctioneers. Mr Miller said: 'The photos themselves are fairly unremarkable but what they represent is astonishing.' The archive will be sold at Charles Miller Ltd in London on October 30.