Unveiling the Unsung Heroes: How Hydrographic Surveying Shaped D-Day’s Success

June 6th, 2024, marks the 80th anniversary of one of the most pivotal events in modern history: D-Day, the Allied invasion of Normandy. This historical milestone underscores that victory in warfare hinges not only on military might but also on the meticulous planning that precedes it. While much has been written about the bravery of the soldiers, sailors, and airmen who took part, few know the story of the unsung heroes who made it all possible – the hydrographers.

D-Day, or Operation Neptune, saw over 156,000 Allied troops land on five beaches along the Normandy coast, marking the largest amphibious invasion in history that was meticulously planned and executed. However, D-Day was not the first attempt to breach Hitler’s “Fortress Europe.” The ill-fated Dieppe Raid of August 19th, 1942, had ended in disastrous failure with over 3,600 Allied casualties. This failure highlighted the consequences of inadequate surveying and planning of deployment and landing, lessons that led Allied thoroughly planned D-day a year in advance to avoid past mistakes. A small naval survey unit of two experienced hydrographers was formed to verify the best available charts, which dated back to 1875, detailing offshore depths in the area.

Hydrography : Now And Then

An LCP (Survey) off Normandy on 7 June 1944. The nearest figure if Lieutenant Nisbet Glen, who helped crew landing craft on two COPP operations (Photo by COPPsurvey.uk)

Top-secret hydrographic survey operations were conducted to gather detailed information near the beach for the design and installation of Mulberry harbors and the landings. To ensure landing craft would not be grounded far from shore due to shallow beach gradients, Allied were doing remote sensing by aerial photography to measure beach gradients. However, these measurements required supplementary ground surveys due to their lack of precision. This task, not for the faint-hearted, was conducted mainly under the cover of night darkness due to the entire coast being heavily guarded, mined, and monitored by the Nazis.

Back in 1943, hydrographic surveys were conducted using equipment like the taut wire measuring machine and a primitive echosounder developed in 1930. These tools, deployed on Royal Navy survey vessels, meticulously measured depths at regular intervals. This data was instrumental in understanding the underwater landscape and planning the invasion routes and empowered commanders to formulate strategic plans with unprecedented precision, ensuring the success of the invasion.

The two lines of soundings taken during Operation Bellpush Charlie. (Photo by COPPsurvey.uk)

Fast forward to 2013, an expedition embarked on a monumental task to create a comprehensive archaeological map of the seabed off the D-Day beaches to commemorate 70th Anniversary of the invasion of Normandy. This collaborative effort with the United Kingdom Hydrographic Office (UKHO) and the French nautical charting authority (SHOM) aims to update the international wreck database for the area.

Covering 511km2 over 27 days, the team utilized advanced technology from an Edgetech 4600 Side scan Sonar and R2Sonic 2024 UHR Multibeam Echosounder and other supporting sensors and software to identify 300 wrecks and obstructions.

Chart showing the bathymetric data collected with an overlay of obstructions and wrecks found during the 2103 expedition. (Photo via Hydro International)

The survey involved 176 lines of data collection, with a single 40-kilometer line taking 5 to 6 hours to complete. On days when the boat surveyed continuously for 24 hours, the total number of soundings reached around 240 million, with the overall dataset amounting to over 11 Terabytes of data.

With the ultra-high resolution sonar system, the crew collected high-resolution point cloud data for about 20 ‘new’ historic assets of particular interest. By having higher resolution images and precise point cloud data, the crew is hoping to determine the actual ship, aircraft or vehicle name of the artifacts revealed. With this information, historians will also endeavour to derive names, ranks and associations of the crewmembers that were aboard the vessels or vehicles when they were sunk and destroyed.

The wreck of the Auk-class minesweeper HMS Pylades sunk by a German midget submarine during the night of July 8, 1944 while anchored as part of the Trout defensive line (see HMS Magic above). The wreck is lying on its port side with the bow to the top. The ship’s superstructure is still clearly evident to the left while the partly upturned hull forms the shallowest part of the image. (Photo via Marine Technology News)


Sonic 2024 – UHR – Charles Brennan – Normandy (Photo via R2Sonic LLC)


Technological Evolution in Hydrography

The evolution of technology in hydrography since the time of the Normandy invasion is nothing short of remarkable. From the rudimentary tools of the ‘40s to the cutting-edge equipment utilized in modern times like R2Sonic 2024 UHR Multibeam Echosounder, the strides made in precision, efficiency, and data collection capacity are astounding.

Sonic V Series from LakeBed 2030 with VOX-IM appeared on top of the box. 
A closer look at the new VOX-IM

The technology of R2Sonic 2024 Multibeam Echosounder and its Sonic™ family is now developed into Sonic™ V and Sonic™ V+ series. The Sonic™-V Series upgrades the traditional Sonic™ multibeam range with a compact VOX-IM unit that will replace the classic SIM Box with all new Sonic™-V Series and Sonic-V PLUS systems. It has these additional features:

  • AC and DC power input
  • Integrated connectors for additional motion/GPS equipment
  • RTK / RTCM input (for Sonic-V PLUS only)
  • Smaller size

With embedded IMU and single cable, it enables users to eliminate the need for multiple patch tests with less risk of exposure and is highly immune to GNSS outages. The VOX Control User Interface gives a modern interface that is agile, intuitive, and user friendly.

For more information about R2Sonic 20204 V, Sonic™ V and Sonic™ V+ series, please contact Geotronix.


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