The History of Aerial Surveying

Introduction By Patrick Ryan 

As the President of the Airborne Sensor Operators Group (ASOG) Association, I've had the pleasure of meeting and getting to know one of the mainstays of modern-day commercial Aerial Surveying – Lyndon York. 

When the editors at AvBuyer asked me to look at some notes and photos Lyndon assembled regarding his long flying career and the history of civil aerial aviation, I happily accepted their offer. However, after going through his notes and photos, it became apparent that the story of Aerial Surveying and Lyndon’s professional life as a navigator and sensor operator needed to be told.

Lyndon York’s story is not just about his professional life but also the history of the late 20th century Aerial Surveying & Mapping sector and the unique aircraft that made it happen. The following article is based on Lyndon’s notes and a few discussions I had with him regarding the history of Aerial Surveying and the part he played in this critical Aerial Work aviation sector. 

Aerial Surveying & Mapping

Since the 1920s, Aerial Surveying and the professional home of Lyndon York have come a long way from glass plate cameras and open cockpits. Today’s aerial surveying operates using precise mapping sensors €1m+, which record information in the visible spectrum and far into the invisible bands. Today’s sensors are large-format cameras, LiDAR, SAR, magnetometers, electro-optical, infrared, multispectral, hyperspectral sensors, and many others. 

Today, these different types of sensors are flown onboard various aerial platforms, all of which support different tasks, e.g., looking for minerals, supporting construction projects, conducting environmental research — albeit in airplanes produced in the 60s and 70s.

The average age of current survey modified aircraft is 40-50 years old but they’re integrated with sensors about ten times the airplane’s value! A modern sensor has a life of about three years, primarily due to rapid advances in digital technology, while still mounted in an airplane going back to the 1960s and 70s. 

The Birth of Aerial Surveying

To get the proper perspective of Lyndon’s story and the world he operated in, you have to understand the history of Aerial Surveying that he helped write. 

If you didn’t know, aerial surveying started in the American Civil War by aerial photographers (the first Airborne Sensor Operators) taking photos from hot air balloons, which became invaluable for monitoring enemy troops and gun positions. Also interesting, aerial photographers experimented using miniature cameras mounted on pigeons and kites during this time. With the introduction of fixed-wing aircraft, aerial photography or aerial surveying expanded to new heights. As soon as airplanes became more capable and reliable, they were improvised to carry out more precise aerial imagery. 

Technology Improves

During World War I, cameras were adapted for vertical usage and became an essential tool for reconnaissance and mapping tasks. After World War I, with the availability of surplus airplanes from the likes of Vickers and Fairey, aircraft were used to map European colonies in Africa and India.

During the ‘30s and with the development of large-format cameras, more modern airplanes were being designed and adapted for mapping missions. One such aircraft was the Abrams P-1 Explorer. An essential feature in any aerial survey airplane was for the navigator to have good forward visibility, hence the fully glazed nose.

During the 30-40s aeroplanes like the Avro Anson.Airspeed Oxford, DH Rapides plus other cabin types were modified to carry these heavy survey cameras.

Before and during WW2 camera and aeroplane technology progressed very fast Camera like Williamson F24 and Fairchild 17 were installed in Spitfires, Blenheim, Mosquitos, plus many other types. Whereby floor and side hatches could be installed. 

A New Industry Emerges

After World War II, various ex-military aircraft became available to civilian aerial survey operators. These aircraft were easily modified with floor hatches enabling large format cameras to be vertically mounted and plumbed into the airplane’s electrical and vacuum systems were needed to flatten the film during the exposure time. 

Many of these surplus aircraft like C47b Dakota, B-17 Flying Fortresses, and B-25 Mitchell bombers were highly suited to carry large, heavy cameras, which proved their worth during the post-war period. 

The basic requirements for a post-war survey aircraft was six hours or more endurance, carrying a camera weighing 300lbs or more, and providing for a crew of 3-5 individuals. The ideal requirement was up to 9 (or more) hours of endurance and operating comfortably above 20,000ft. 

The 1950s

The 1950s saw the emergence of civil aerial survey companies whose operations spread far and wide throughout Europe, and beyond. 

Companies like Aircraft Operating Co. (later Hunting Aerosurveys) and Fairey Air Surveys, mainly equipped with C47b Dakota, were established to map the UK and its colonies. The Hunting Aerosurvey C-47s were fitted with P&W 1830-92c engines with two-stage superchargers enabling operations at higher altitudes. 

The 1950s began with cameras only, then came magnetometers. Aerial surveying magnetometers were directly descended from the Magnetic Anomaly Detectors (MAD) used on anti-submarine aircraft. These tail-boom mounted sensors were primarily integrated on C-47s and extensively used for oil and mineral surveys over the North Sea and in other remote areas. 

Besides domestic surveying, overseas aerial surveying operations would see a crew away from home for months in countries like India, South Africa, and Canada. During this period, companies like Hunting Survey and Fairey Air Surveys established locally registered companies in these locations and later became independent operators. Some of these firms are: 

• Adastra Aerial Surveys - Australia (Lockheed Hudsons and AVRO Ansons) 

• Kenting Aerial Surveys - Canada (Boeing B-17s, DH Mosquitos, Ansons, P-38s, PBY Catalinas) 

• New Zealand Aerial Mapping Co. - New Zealand (General Aircraft Co. Monospar ST-25s) 

During this timeframe, many aerial survey companies tried various other types of aircraft like the Hurel-Dubois HD.34 and Edgar Percival E.P.9. However, the venerable C-47/DC-3 remained the most suitable platform for long-range operations. 

Near the end of the 1950s, the 1940s aircraft became relatively expensive to run and maintain. As a result, newer types og aircraft like de Havilland DH.104 Dove and Scottish Aviation Twin Pioneer were added to the aerial surveying community. Over time, these aircraft proved useful as aerial surveys platforms.

However, many non-profit government aerial surveying agencies like the French IGN (Institut National de L'information Géographique et Forestière) continued to operate earlier model aircraft like the Boeing B-17 well into the 1970s. 

The 1960s

During the 60s and onwards, oil and mineral surveying and other industry sectors increased the demand for aerial surveying. Along with this, sensor technology and its availability expanded tenfold. As a result, sensors like surveying radars, ground profile recorders, scintillometers, Synthetic Aperture Radars (SAR), electro-optical cameras evolved as essential tools for highly accurate mapping, mineral surveys, environment surveillance, agricultural monitoring, and numerous other usages requiring millimetre accuracy. 

With all this new technology, aerial surveying aircraft required extensive modifications, e.g., installing radomes, booms, equipment racks, recording systems, additional batteries, APUs, etc. Additionally, to obtain the required accuracy, these aircraft were also equipped with (at the time) precise navigation equipment like Doppler, Decca, and LORAN. 

Companies like Hunting Surveys and Fairey Surveys continued to utilise their C-47/DC-3 aircraft but with heavy modifications. Many of their aircraft had 20ft-long magnetometer tail-booms installed and 500-gallon extended long-range tanks positioned in the cabin, allowing for 12 hours of flight time. Other notable aircraft like Consolidated PBY Catalina Flying Boats proved worthwhile fitted with circular EM antenna arrays. 

By the 1960s, most developed countries had civil aerial surveying companies. However, the countries with security concerns regarding aerial mapping relied on government agencies or military units, e.g., the French IGN provides mapping services within France and former French colonies. 

Besides small aerial surveying companies and large government agencies providing mapping services in the ‘60s, some airlines added aerial survey subdivisions to their corporate structures like BKS Air Transport and KLM. However, many of these airline aerial surveying subdivisions were either sold or disbanded over the years.

The 1970s

During the ‘70s, there were various international hotspots for aerial surveying. One such place was Nigeria. During this time, one would see a line-up of platforms on the tarmac varying from a French B-17, Finnish Lockheed Lodestar, de Havilland DH.104 Dove, DC-3, Percival Prince, plus various other types of aircraft. 

By this time, the demand for strategic minerals like potassium, thorium, uranium, and precious metals expanded the need for aerial surveying. The primary sensors used were magnetometers, spectrometers, VLF recorders, etc. 

The critical requirement for survey platforms was long-range endurance (aircraft with less than five hours were not very viable), high-altitude capability, oxygen systems, high-performance generators, and the ability to carry several hundred pounds of surveying instruments and support equipment. 

Near the end of the 70s, older types of aircraft were getting harder to maintain and sustain, so the first 'Spam Cans', such as Piper PA-23/PA-31, Cessna C-337/C-402, and Beechcraft B80 Queen Air, began to appear in the skies over Europe. 

According to Lyndon, by this time, most aerial survey companies were run by “dreaded accountants in place of flying types. The accountants were not interested in crew comforts, cabin space, or toilets — we had to get out there and just get the job flown.”

The 1980s to Today

From the ‘80s to the present day, the demand for aerial surveying continued at a healthy pace. By this period, the aerial surveying community started to utilise jet and turbine aircraft like Learjets and Aero Commanders. Today, one of the most widely used turbine aircraft for aerial surveying is the 690A Twin Commander series, along with the Piper PA-42 Cheyenne, and Cessna 441 Conquest II. 

Also, during the past few decades, the world switched from analogue to digital, which significantly changed the capabilities and quality of aerial surveying. The process of pre-planning, collecting, and data processing has improved a hundred-fold since the first aerial surveying photos taken on the battlefields of the American Civil War. 

Been There, Seen It, Done It!

As mentioned before, Aerial Surveying and the professional world of Lyndon York have come a long way from glass plate cameras and open cockpits. Since the 1960s, Lyndon has traveled the vast corners of the world while flying civil survey missions in many types of aircraft. 

According to Lyndon, he has operated in over 122 countries; was shot at three times while flying (fortunately, they all missed!); was jailed for spying in three different countries; witnessed the odd ‘coup d'état’; and lost a few flying comrades to survey flying accidents. 

Career Path

Lyndon got his start in aerial surveying with Hunting Aerosurveys Ltd. Besides receiving his initial training as a navigator and operator, he conducted aerial surveying operations in aircraft like the de Havilland Dragon Rapide, Percival Prince, Douglas C-47b Dakota, and Auster J/1-5 throughout Europe, Africa, and the Middle East. 

Following his work at Hunting Aerosurveys, Lyndon went to work for Fairey Surveys Ltd and then for BKS Surveys Ltd. As with Hunting Aerosurveys, he continued to fly a variety of exceptional aircraft around the globe, including the de Havilland DH.104 Dove, Douglas C-47b Dakota, Beechcraft B80 Queen Air, Scottish Aviation Twin Pioneer, Avro Anson Mk.19, Beechcraft Model 18, and later the Cessna 336 Skymaster and Piper PA-23.

After completing his ‘tenure’ with some of the most notable aerial surveying companies in the UK, Lyndon decided to become a freelance aerial surveying navigator and operator. He continued to travel the far reaches of the planet while flying in some fascinating aircraft like the Antonov An-2, Antonov An-26, and Beechcraft Baron B55. Following these older airplanes, he started flying in more modern ‘Spam-Cans’ like the 690A Twin Commander series, Cessna 404 Titan, and Piper PA-31 Navajo. 

Outside of flying in civil-type aircraft, Lyndon also flew in some converted World War 2 bombers like the A-26 Invader/On Mark Marksman and the Boeing B-17 Flying Fortress in adventurous locations such as Africa. 

Favorite Aircraft & Memories

There are always notable or memorable events, people, and aircraft one encounters with any aviation career. But, when it comes to Lyndon, he has some favourites: 

Hunting Surveys Ltd – de Havilland Dragon Rapide (G-AIYR)

G-AIYR was built in 1943 and served in the RAF until the war’s end. After the war, Hunting AeroSurveys purchased G-AIYR and based it at Elstree Aerodrome, where Lyndon started his career. He never forgot the smell of G-AIYR’s fabric, dope, and oil. 

G-AIYR was fitted with long-range internal tanks but often ran out of oil before fuel! During its surveying years, G-AIYR operated throughout the UK and even carried out a survey mission in Jordan, where the ailerons warped in the heat! Today, you can find G-AIYR conducting pleasure flights from Duxford. 

As a fun side-story regarding Lyndon and G-AIYR, years later — when Lyndon was working in Zambia in the ‘70s and preparing to fly his modern Cessna 404 Titan on a survey mission —he heard a strange but familiar sound. He was amazed to see a de Havilland Dragon Rapide flying over the airfield as he looked up. Then, as Lyndon and his pilot turned on their VHF radio, they heard a very familiar call-sign – ‘G-AIYR! It turned out to be an old friend (David Sisters) flying the historic Sir Allan Cobham pioneering route from the UK to South Africa with G-AIYR. Without delay, Lyndon and his pilot took off. They chatted with David over the radio, where he could fill him in on G-AIYR’s surveying history while taking a few pictures of G-AIYR with his survey camera. As Lyndon noted – “It can be a small world!” 

Hunting Surveys Ltd – de Havilland Dragon Rapide (G-AHED)

Hunting Surveys also operated G-AHED. This aircraft was built in 1946 and, according to Lyndon, had an entirely different smell to G-AIYR! Like G-AIYR, G-AHED also operated throughout the UK from Elstree Aerodrome until donated to the Royal Air Force Museum in 1968. 

One of Lyndon’s most notable experiences with G-AHED was on a survey flight to Shannon, Ireland. At the time, G-AHED had auxiliary long-range fuel tanks installed in the forward cabin. A few miles out over the ocean, the left engine started spluttering, and it soon became evident that the auxiliary fuel tank was not feeding due to a frozen valve. So Lyndon and his pilot had to land at Swansea, Wales. Coincidently, the date of this flight happened soon after Ronnie Biggs, the great train robber, had escaped from prison. 

After landing and the valve was freed up, they launched again, but a few minutes later, the same problem occurred once more, so they returned to Swansea for another attempt of repairing the problem. After landing the second time, ATC thought this was very suspicious, and they were ordered to stay in the aircraft until they received some visitors. After waiting for some time, the police arrived and searched the cabin for Mr. Biggs! Needless to say, Lyndon and his pilot eventually reached Shannon! 

Hunting Surveys Ltd - Douglas C-47b Dakota/DC-3 (G-ANAF)

Besides operating Dragon Rapides and other platforms, Hunting Surveys also operated Douglas C-47s for long-range and endurance operations, e.g., North Sea, etc. G-ANAF is a C-47b or DC-3 and was routinely outfitted with various sensor ans kits that other surveying aircraft couldn’t accommodate. Currently, G-ANAF is still flying as an R&D platform. 

Like with G-AIYR and G-AHED, Lyndon’s exploits continued. While conducting aerial surveys in Liberia with G-ANAF, Lyndon and his crew suffered an engine failure over a very remote area of the country. Fortunately, they could find and land at a plantation airfield some 200 miles from their home base in Monrovia. Because there were no telephones or other means of communications, Lyndon was ‘elected’ to find a taxi and report back to Spriggs Payne, the main airport at Monrovia. 

At the time, not one person at the plantation airfield was bothered about their situation except for an elderly German gentleman with a battered Cessna C180. It turned out that this gentleman was a POW in the UK during the war and felt very grateful to help the crew with their situation. After reporting the problem, Hunting Surveys delivered a spare engine and a sheer-leg lifter aboard a sister C47. After a short period, Lyndon and his crew were able to replace the engine and continue the survey project. 

Summary

As you can see, Lyndon York’s story is not just about his professional life but also the history of Aerial Surveying and the aircraft that made it happen. Since the 1920s, Aerial Surveying and the professional world of Lyndon York have come a long way from bail-wire aircraft and wet-film cameras to digital systems that can survey far beyond the human eye with precision and accuracy. 

Like so many legends of a profession or industry sector, they never really stop. In the case of Lyndon – old navigators never die, they just point the way! Today, Lyndon is still hard at work in the aerial surveying sector by consulting and brokering aerial survey aircraft, sensors, and crew kits through his company Trackair Services Ltd. Along with this, he launched AERIALSURVEY.com, which is now part of ClearSkies Geomatics. 

To sum it all up, If you ask Lyndon if aerial survey aircraft are still required or if satellites and drones can do the same job, he would reply with, ‘They Can't!’