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Aero Service Corporation[edit]

This provides details of the company known as:

  • Aero Service Corporation. Headquartered in Philadelphia Pa. [1919 - 1961].
  • Aero Service Corporation, a Division of Litton Industries. Headquartered in Philadelphia Pa. [1961 - [1973].
  • Aero Service Division of Western Geophysical Company of America. Headquartered in Houston Tx. [1973 - 1990].

Aero Service was a provider of:

  • Aerial Photo Mapping and Surveying Services [1924 - Aug 1990]
  • Airborne Geophysical Services [1945 - Aug 1990]
  • Airborne SAR Mapping [1970 - Aug 1990]
  • GPS geodetic services [1986 - Aug 1990]

Aero Service was incorporated in 1919 and provided air taxi services and oblique aerial photo operations in the area around Philadelphia.

Aerial Photo Mapping[edit]

A former WWI pilot Virgil Kauffman[1] purchased the company in 1923 and expanded aerial photo services to include vertical photography. The camera was mounted to look through a hole in the floor of the aircraft. Photo mosaics were created from this vertical imagery.

Other Early Pioneers[edit]

Other Aerial Survey companies came into operation after WW1 {more}

Abrams Aerial Survey Corporation[edit]

Talbert Abrams[2] formed Abrams Aerial Survey Corporation in 1923. {more}

Fairchild Aerial Surveys[edit]

Sherman Fairchild founded Fairchild Aerial Camera Corporation in 1920 [citation needed] and created cameras specifically designed for aerial photography. In 1921 he founded Fairchild Aircraft and designed aircraft to be used as aerial mapping platforms for these cameras. The first of these aircraft was the FC-1 and was also novel in that it had an enclosed cockpit.

Brock System[edit]

Overlapping vertical photographic images were used to create topographic maps. A solution to the creation of topographic maps from aerial photographs was made possible by use of cameras and stereographic plotting equipment developed by the Brock Brothers of Brock and Weymouth [citation needed]. The camera used in the Brock system was invented by Edward H. Cahill[3].

Beginning in 1925,[citation needed]} Aero installed the Brock Cameras in some aircraft and installed the plotting systems in the Philadelphia office.

In the early 1930's, Aero Service purchased the rights and patents of Brock and Weymouth.[4]

{need much more information on activity late 20's up to beginning of WWII and what transpired with Brock Process and competing technologies}

Field Surveying[edit]

A Survey department was created to provide control information for the aerial photography.

{Lots More}

Kelsh Stereo Plotter[edit]

The United States Geological Survey used a photographic image stereo plotter that was simpler to set up than the Brock process and this was used by Aero Service and others. The plotter was the patented invention of Harry T. Kelsh and the U.S. Government[5] was provided its use royalty free.

{believe this was in 1945. Need more information}

High Altitude Photography Post WWII[edit]

Aero Service acquired high altitude photography 18,000 feet and higher] in the late 1920's with single radial engine aircraft such as Cessna and Fairchild. Post WWII, US Government sponsored aerial mapping in various locations around the world was performed using Lockheed P38 and B17 aircraft. Many of the B17 operations used SHORAN[6] guidance. The use of SHORAN required heavy logistical support for the ground station installation and crew support. These SHORAN operations were performed in Saudi Arabia, Iran and South East Asia.

Some foreign high altitude photo mapping projects were conducted by World-Wide Aerial Surveys, a joint venture between Aero Service and Fairchild Aerial Surveys.


Orthophotographic devices were developed in the '50s. These devices scanned the aerial photos to produce an image of constant scale.

Other Services[edit]

Aero became involved in other Services and Products in the post-war period. Perhaps one of the most notable was the creation of Raised Relief Maps.

Raised Relief Maps[edit]

This became a thriving business for some time. Many thousands of these plastic relief models of various areas of the U.S. and other countries were sold, including world globe models.

The business was eventually sold to Nystrom in 1965[7]

Raised Relief Models[edit]

These were created for military, civil engineering and construction projects.

Battle Field Simulation Models[edit]

These were created for the US military for various purposes and signatures such as Radar Response or simulated Infra-red signature of a battle field.


A mobile road surface inspection system using a modified Aero strip camera to provide photo strips of road surface for analysis of road surface conditions.

Introduction of Airborne Geophysical Instrumentation[edit]

During WWII, Aero had been involved in classified work, both in mapping operations and the evolving airborne magnetometer system designed for submarine detection. [citation needed]

{Insert here object of magnetic surveys [sedimentary basin or hard rock mineral etc Mention interesting things found that were not the survey objective such as the Chiclub impact crater}

As demand grew, Aero developed subsidiary relations with various groups in other countries. The most significant operation outside the U.S. was in Canada. During the early 1960's Aero Philadelphia and Canadian Aero in Ottawa had the services of more than 30 aircraft. In addition to Canada, Aero Service had affiliated operations in France, South Africa, Rhodesia and Australia to name a few. These operations included both Geophysical and Aerial Photo surveys.

Comparison to currently available Instrumentation and Navigation Systems[edit]

Much of what follows reflected the state of the art at the time.

The following is now possible: -

  • World-wide availability of real-time Differential GPS with meter-level or better position accuracy,
  • 100 Hz high resolution magnetometer data sampling to allow dynamic compensation.
  • In-flight presentation of flight and traverse line presented on a map base such as Google earth or other.
  • Powerful lightweight digital recording systems and recording media
  • Internet access

Airborne Magnetometer[edit]

During WWII, Gulf Oil Research and Development worked with the US Government to develop the Airborne Magnetometer for anti-submarine warfare. This device was invented by Victor Vacquier and was a self-orienting fluxgate magnetometer providing a measure of the total field intensity of the earth's magnetic field. After the war, Aero Service used this device for geophysical prospecting. Gulf Oil Research and Development leased systems to Aero and others. This device provided the means for airborne prospecting initially for iron ore deposits and later defining the depth to crystalline basement, allowing the definition of certain types of sedimentary basins in the exploration for oil. Such airborne surveys were able to cover hundreds or thousands of square miles and allowed better use of ground exploration assets such as seismic and exploratory drilling to be more focused on potential economic areas.

The magnetometer was installed either in a 'bird' towed beneath the aircraft, or in a tail 'stinger'; an extension to the tail of the aircraft which incorporated 3 mutually orthogonal coils to compensate for the permanent and induced fields of the aircraft. Direct current through these coils created the compensating field. MuMetal strips were also a requirement.

Aero established a subsidiary company, Canadian Aero Service Limited to provide airborne geophysical services in Canada. Canadian law required that aircraft registered in Canada be owned by a majority-owned Canadian company so an agreement was reached with Spartan Aero Services to provide the aircraft. The primary targets in Canada were for minerals, so Electromagnetic Systems also become a requirement.

In 1964 Aero purchased a Rubidium Vapor Optically-pumped high sensitivity magnetometer from Varian Associates. This was an increase of sensitivity approximately two orders of magnitude over the Gulf Fluxgate magnetometer. At this time, Aero also started to develop a system to digitally record data to ½ inch IBM compatible magnetic tape.

In 1966 Aero signed an exclusive contract with Varian to supply Cesium-vapor 6 cell Omni-directional magnetometers. These were used in towed bird configuration with one bird flying below the other to measure the total magnetic field intensity at two elevations. Initially 4 DC3 aircraft were outfitted with these magnetometers. All of these aircraft were equipped with a new digital recording system built by Lancer Electronics, a local company in the Philadelphia area.

In 1974, Aero purchased Split-beam Cesium Magnetometers from Varian Canada for installation in Piper Navajo and Cessna 404 aircraft.

Tracking Camera[edit]

The flight path of the airborne survey was captured by a specially constructed 35 mm tracking camera. The camera had a 0.01 inch slit to expose the continuously moving film. The result is a continuous strip of the flight path. An event counter known as the 'fiducial' counter was exposed at prescribed intervals at the edge of the frame. The pulse that triggers this counter also provided an edge [fiducial] mark on the magnetometer chart record tying the film path to the observed data.

Some frame cameras were used and were preferred by some of the path recovery personnel, but they were more likely to jam in flight than the continuous strip camera.

Video recording was used by some competing companies in later years.

Radar Altimeter[edit]

A radar altimeter is used to show aircraft height above ground. An early radar altimeter used with some aircraft was an AN/APN-1 operating at 440 MHz. Some aircraft flying contour or 'drape' may have recorded the output on a single trace chart recorder.

Later installations used an AN/APN-171(V) manufactured by Honeywell. Most installations starting in the 1960's had these altimeters. These data were always recorded in later installations, both to paper chart and digital tape.

Barometric Sensor[edit]

When digital data recording was installed, barometric altitude was also recorded. DC3 installations with high sensitivity magnetic sensors had a pressure port calibrator to record deviation from a preset altitude. Rosemount 1241 Barometric sensors where installed in later Aero Commander, Piper Navajo and Cessna 404 installations. These data were digitally recorded.

Electromagnetic Sensors[edit]

As use of the airborne magnetometer became more widespread for mineral exploration, additional methods were applied, particularly in Canada. Early Electromagnetic Sensing systems were frequently unique to each survey organization. An early simple fixed wing system comprised a transmitter loop excited by a 1 kilowatt 400 Herz inverter with a towed 'bird' with receiving coils in quadrature. These systems provide conductivity measurements of the near surface beneath the aircraft. Later systems operated at three frequencies. Anthony Barringer[8] created a pulsed system named INPUT [Induced Pulse transient] The fixed wing aircraft versions of these systems were frequently mounted on PBY5A [Catalina] and its variants. Many of the new systems are helicopter-borne

Other Airborne Sensors[edit]

During the first years post WWII, Gamma ray Scintillation detectors were installed for surveys in mineral provinces. These provided some basic responses to varying surface geology. In the '60s, this evolved to discriminating between various energy levels with analog Gamma Ray Spectrometer systems. Separate recording channels for Potassium [K40] 1.46 MeV, Uranium [Tl214] 1.76 MeV and Thorium [Bi214] 2.61 MeV. Uranium and Thorium presence is inferred from the Tl214 and Bi214 daughter products respectively. In the early '70s, requirements of the USGS and Natural Resources Canada resulted in the use of digital Gamma Ray Spectrometer systems employing large arrays of detectors including 'upward looking' arrays for cosmic ray compensation and atmospheric inversion-trapped radon detection. Both agencies established calibration pads that were used by the various airborne contractors prior to departing to survey areas. The U.S. NURE program surveyed every 1:250,000 map quad in the lower 48 states and Alaska. Some of these systems were deployed in helicopters.


Some Airborne Magnetometer Surveys were conducted using SHORAN for navigational guidance. One of the earliest surveys conducted in 1946 over the Bahamas used SHORAN. Offshore surveys in Australia in the Bass Straight in 1961/62 and the Great Barrier Reef in 1963 used SHORAN for guidance. Due to the line-of-sight requirement and the relatively low altitudes [2000 feet or less] this required a large number of manned reference stations with the attendant operational cost.

Doppler Radar Navigation Systems[edit]

Onshore, airborne geophysical surveys used topographic maps or photo mosaics for navigation. The maps or photo strips had flight lines drawn on them for use by the crew in guiding the aircraft, and recovering the flight path using a 35 mm film of the flown line. A problem in many areas was that there were no useful maps or photo coverage. In 1961[?] in Libya, Aero used a Doppler Radar navigation system for guidance on geophysical surveys. This system provided ground speed and drift angle. Drift angle together with heading from a magnetic-slaved gyrocompass were combined to produce course made good. Ground speed and course made good were inputs to an analog navigation computer. The computer had settings for pilot selection of line heading and distance to go. The system used in Libya was a General Precision Laboratories RADAN 500 and the navigation computer was a TNC 50. The gyrocompass was a Kearfott N1. The RADAN 500 had a gimbaled antenna and made extensive use of analog tracking loops to determine steer the antenna and determine along and across track velocities. While quite accurate [citation needed] it required very careful adjustment. Aero used this same system in Australia in an Aero Commander for a survey in the Great Sandy Desert. Subsequently when the entire fleet of a dozen or so aircraft were converted to Doppler Navigation, Bendix DRA12C X-band systems were used in combination with a Sperry C11 Magnetic Slaved Gyrocompass system. The Sperry system had a more advanced magnetic compensation system for the heading sensor. The Doppler antenna was fixed and switched four spot beams; Front Port, Front Starboard, Rear Port and Rear Starboard. The Tracker module was a hybrid analog/digital system. The digital trackers combined the results from the Doppler shifts of the return beams to provide ground speed and drift angle as with the GPL System and into a similar analog/mechanical navigation computer.

The ground speed measurement was used in two other systems:

  • An output of frequency proportional to groundspeed was down-converted so that the output was 60 hz at the no-wind ground speed. The camera motor was replaced with a 60 Hz synchronous motor. Tests showed that the motor will remain synchronous over the range 45 - 75 Hz so the film strip speed is controlled by ground speed This approximates a constant along track scale for the film, the only variability being due to change in height above ground.
  • Similarly, the analog chart recorder was also had a synchronous motor driving the paper. This provided a constant scale for the along axis of the chart, and constant distance 'fiducial marks' on the edge of the chart from a count of the ground speed frequency pulses.

Digital Doppler Navigation Computer[edit]

A Digital Doppler Navigation Computer was developed in 1975, replacing the existing electro-mechanical unit. It accepted ground speed frequency and synchro inputs of magnetic heading from the C11 gyrocompass and drift angle from the Doppler system. The Cockpit-mounted Control Display unit had pilot selected course and distance to go and displayed along course / across course position. This computer used an Intel 8008 microprocessor.

Data Recording[edit]

Data from the Geophysical Instrumentation was recorded on paper chart prior to the mid 1960's. The first change to this was tested in an aeromagnetic survey of the North Sea in 1963 in an A26. Punched paper tape was used to record data. This aircraft also made some flights using Inertial Navigation [citation needed] and LORAN C. In 1966, a high sensitivity Rubidium vapor magnetometer was installed in a 'tail stinger' of a DC3 N5000E. A hand crafted digital system recorded the magnetometer and radar altimeter data to 7 track 1/2 magnetic tape. This was in parallel to the conventional paper chart recording. Digital data processing at the Philadelphia office was under development using an IBM System 360/44 in parallel with conventional handling of the paper records. It would be some time until digital contour mapping routines sufficiently matured to eliminate hand contouring.

Digital Recording[edit]

A significantly more sophisticated Digital Data Recording System was developed in-house in 1974. This system recorded to 9 Track IBM Compatible 1/2 inch tape.

A Hewlett Packard minicomputer-based data acquisition system was developed in-house in 1978?.

  • This provided the ability to play back in the field for Quality control purposes.
  • This also gave the ability to copy field tapes for added security.

Other Navigation Systems[edit]

At various times, Aero used other navigation systems. Some of these navigation networks were in place in a survey area and used by others such as seismic contractors. These systems included Decca, Raydist, Del Norte Trisponder,Prakla ANA, LORAN C, Inertial Guidance.

Aero created a variant of Western Geophysical's WINS [Western Integrated Navigation Computer] using a minicomputer from HP that provided a position solution from a Kalman Filter that used ranging data from multiple systems to provide a system position.

As an example, during a project in the Yucatan peninsular, Aero established multiple PRAKLA ANA transmitter sites. The ANA system was a medium frequency phase comparison system that relied on Atomic Frequency standards at the transmitter sites and the mobile [aircraft] receiver to precisely determine the phase at the receiver. Since the system was un-modulated, the 'lane count' [number of wavelengths to the transmitter sites] had to be independently determined. The original method was to fly over a known point where the lane count to two or more transmitter sites was known and carry that number plus the phase provide intersecting lines of position. The ANA system had an effective range of 600 km during daylight hours.

A Del-Norte X band Trisponder system was also used to provide precise ranges to 2 or more ground transponder sites. The transponders ranges are limited to line of sight. Flying within the range of the transponders allowed automatic 'lane count' identification for the ANA system. The survey area was onshore and offshore several hundred kilometers so traverses from the coast to the outer limits of the survey area were effectively controlled.

Such a ground-based system was also used to correct position from an Inertial Navigation system that drifts over time.

Another application used LORAN C with an Atomic frequency reference to operate in a 'range/range' mode rather than the standard hyperbolic mode.

Diurnal Magnetic Storm Monitor[edit]

During the acquisition phase of an aerial magnetic survey, a magnetic base station monitor ran 24 hours to verify the absence of magnetic storms. The early implementation of this consisted of a fluxgate sensor and paper chart recorder. Prior to each days flight, the chart would be reviewed to determine that the trend in changes to the magnetic field intensity was below a specified rate.

Diurnal Magnetic Storm Monitor Digital Recorder

Later versions of this monitor included alkali vapor magnetic sensors and digital data recording.

Geophysical Survey Design[edit]

Flight pattern layout was determined by target objectives and any a-priory knowledge of the geologic trends in the survey area.

A typical survey for oil exploration purposes might have a grid with traverse line spacing of 2 miles and intersecting tie lines at 10 mile intervals and flight elevation of 1500 feet above mean terrain.

The tie lines were used to tie the navigation with common points in the intersecting tracking camera images and also to level the magnetic observation set.

Mineral exploration grids were generally more closely spaced and were flown at 500 feet or less above in a terrain following mode.

During field operations, a field data analyst would develop the 35 mm film from the tracking camera each day and review the recovered flight against the flight map or photo strip, and also pick intersecting points in the traverse/tie line film. Any re-flights were determined from this film review.

Geophysical Data Compilation[edit]

Aero compiled almost all of the data acquired during its airborne survey contracts. The end products usually took the form of magnetic contour maps showing anomalies in the total field intensity.

{Much more needed: flight path recovery, leveling, contouring; evolution to digital processing}

Geophysical Data Interpretation[edit]

Aero also provided geophysical interpretation of the results, although some clients occasionally performed their own interpretation or used a third party.

{More needed including rtp, Werner deconvolution}

Other Services in Houston[edit]

Certain other services were offered when the company moved to Houston

Gravity Data compilation[edit]

Aero compiled Marine Gravity data collected by Western Geophysical crews.

Utility Mapping[edit]

{insert details}

Geographic Information Services[edit]

{insert details}

Synthetic Aperture Radar[edit]

Equatorial areas of the world were frequently sparsely imaged due to cloud cover. Radar imaging offered the ability to image through this cloud cover.

Aero Service / Goodyear Aerospace[edit]

In 1970, Aero Service acquired a Sud Aviation Caravelle VIR N1001U from United Airlines. A joint venture with Goodyear Aerospace installed a modified AN/APQ 102 Synthetic Aperture Radar [SAR] system called GEMS [Goodyear Electronic Mapping System] in the Caravelle. This was a X-Band [3cm] system with approximately 10 meter resolution. Data in the form of phase returns was recorded to 7 inch panchromatic film. These data were used post-flight as input to an optical correlator that produced the final image strip.

Aero Service Caravelle VIR N1001U

Inertial Navigation [LTN51] was used for aircraft guidance. A feature of the GEMS system was integration of the inertial system to stabilize the SAR antenna including the loop controlling the antenna steering of the real aperture and uniquely controlling the beam steering. This was important where the imaged area had large portions of the imaged area with water.

{Needs severe editing}

Image Mosaics[edit]

The delivery product consisted of controlled mosaics created from the overlapped flight strips.

Imaged Areas[edit]

Venezuela and Brazil had poor photographic coverage at the time. Certain areas of Venezuela were imaged. Aero formed an association with LASA in Brazil conducted a program known as Projecto Radam. All of Brazil was imaged in two separate projects. This image now forms a baseline for deforestation that has occurred since that time. A unique operational requirement for the Radam project was the use of SHORAN to provide positioning constrains on the assembled mosaics.

Additional surveys were conducted in Liberia, Gabon, Indonesia, and Alaska including the Aleutian chain. Many of these imaged areas included interpretation for morphology and surface geologic characteristics.

{More ?]

GPS System Development[edit]

In the early 1970’s Space Astronomy researchers developed a technique to make high precision geodetic measurements from Very Long Baseline Interferometry observations. This technique recorded incoming wave fronts from distant galactic sources together with accurate clock information derived from an Atomic clock at the receiving sites. At the time of the launch of the 1st GPS Satellite in 1979, researchers at MIT led by Dr. Charles C Counselman conceived a method to use earth orbiting satellite transmissions to perform a similar function to VLBI Geodesy in measuring the incoming wave front from the carrier phase of the satellite signals. This technique did not require knowledge of the ranging code modulating these signals. This system, known as Miniature Interferometric Terminal for Earth Surveying [MITES] was first demonstrated in 1978. Dr Irwin Shapiro an Astro Physicist then at MIT was a collaborator in this endeavor. Dr. Counselman worked with Dr. Donald Steinbrecher to create a system called the Macrometer V-1000 Interferometric Surveyor. This system recorded carrier phase measurements of the L1 frequency of the GPS satellite system. A pair of these instruments could determine the baseline between the antenna phase centers of each of the instruments to significant accuracy. Steinbrenner was the President of Macrometrics Inc. which manufactured the Macrometer Interferometric Surveyor.


Aero Service bought Macrometrics in 1984, and continued producing Macrometers for a few more years. A later model [V-2000] recorded both the L1 and L2 carrier phase to allow for correction to ionospheric refraction in post processing of the data.

{Describe Certification and provision of Macrometer services}


Aero developed the MINI-MAC series of GPS Receiver systems in 1988.

  • MiniMac 2816 dual frequency [L1, L2] land surveyor.
  • A tectonic monitoring version [2816AT] was also developed and installed in various locations, particularly in Japan were it was used for earthquake precursor monitoring.
  • Other 2816AT systems were sold to Crustal Monitoring groups in the US, Australia, Norway and Germany.

{Need also to describe services}


Aero Service continued development of the ‘codeless’ technique to create a dual band [L1/L2] marine differential navigation system for Aero Service’s parent Western Geophysical. Dr Charles Counselman and Dr Sergei Gourevitch, part of the original Macrometer development team were consultants, This proof of concept system, internally known as the ‘Marine Machine’ showed that such a system could readily navigate a moving vessel with a recorded position accuracy of 1 meter or better over a baseline of 1000 km. A subsequent system, known as SARGAS was deployed and used by Western Geophysical on their Marine Seismic vessels.

{Describe joint venture with Wimpol and also SARGAS Network}


POSNET evolved from the need to create a system that tracked vessel and off vessel targets such as gun and tail buoy pods used with 3D seismic acquisition vessels. The off vessel targets were tracked differentially from the vessel. The vessel is tracked differentially from a shore reference station, which may be a dual band solution.

{Provide more details}