Imagining Soviet Surveying

Last week I wrote about some of the apparent differences between how the US and the Soviet Union used satellites for mapping and geodesy. The Soviets seem to have been slower to operate dedicated satellites in both areas, with no apparent explanation. Though it’s dubious to use US intelligence estimates as evidence of what the Soviets were actually doing, they do at least shed light on some of the possibilities.

Two CIA reports from from the pre-satellite era, in 1954 and 1957, suggested that if the Soviets had made a connection across the Bering Strait between their own domestic surveys and the North American Datum, missiles launched from near the Bering Strait would have a Circular Error Probable (CEP) of 300–500 feet. Without the connection between datum, the error would be closer to 1,000 feet. without any additional surveys of US territory By making observations of an upcoming solar eclipse and gaining access to the equivalent measurements from US or Western European sites, the CIA predicted the error in intercontinental position could be reduced to about 500 feet from anywhere in the Soviet Union.

These estimates assumed that the target could be located on high-quality American maps, which the analysts presumed were available to Soviet planners. But what if the targets were secret sites not plotted on any maps? A Studies in Intelligence article (“Spy Mission to Montana”) from 1995 revealed that the CIA and Air Force tested those conditions as the silos for Minutemen ICBMs were being built in 1962. A three-person team, two from the CIA and one from the Army Map Service, made covert observations of the sites under construction from their rental car. Dodging both site security and the official survey being done by the Air Force’s 1381st Geodetic Survey Squadron, the covert team proved that observations could be made with a CEP of 600 feet when maps at 1:250,000 scale were available and a CEP of 200 feet with 1:62,500 scale maps.

Did the Soviet Union make a secret measurement of the Bering Strait or send its agents to survey the locations on American missile silos? The answer is probably somewhere in the files of the KGB or GRU.

Soviet Satellites and Mapping

John Davies’ website has announced that his and Alexander Kent’s book The Red Atlas: How the Soviet Union Secretly Mapped the World will be released by University of Chicago Press. Details for the book on the press website show 272 pages and 282 (!) colour plates and a publication month of October 2017. Having read what the authors have written elsewhere about Soviet maps, I’m really looking forward to the book. In particular, I’m hoping it will offer not just more information on how the Soviet military prepared their maps but also some insight into why and for who.

The technical military challenges that drove both American and Soviet cartographic projects during the Cold War were very similar, which leaves the differences in practice between them begging for explanation. Take, for example, the apparent difference in exploiting satellite geodesy. Both countries very swiftly exploited the fact that perturbations in satellite orbits revealed new details on gravity and, by extension, the shape of the earth. They also must have recognized that satellites made better targets for intercontinental triangulation than rockets, stars, or the sun and moon, all conventional targets at the time.

As a result, Sputnik effectively sidelined an American-led terrestrial program of geodetic measurements for the International Geophysical Year that had been under development since 1954. Led by William Markowitz of the US Naval Observatory, using dual-rate cameras of his own design, the program distributed cameras to observatories around the world to make simultaneous moon observations during 1957. Using an approach to triangulation similar to that used during eclipses, the promised precision was to within about 90 feet at each observatory. Uncertainties in the position of the moon meant the 1957 observations never delivered geodetic results, but more substantially the entire concept had been rendered obsolete.

Consequently, in addition to measurement projects that were added to other scientific satellites, the US launched its first dedicated geodetic satellite in 1962. ANNA-1B was a joint Department of Defense-NASA project that carried instruments to enable both triangulation and trilateration. Its launch came only two years after the US lofted its first photo-reconnaissance satellite, which makes sense because both satellites were part of the effort to find and target Soviet strategic missiles.

Intriguingly, then, it was six more years before the Soviet Union launched its own dedicated geodetic satellite. The first of the Sfera series (Russian for “Geoid”) satellites (11F621) flew in 1968, launched from the rocket base at Pleketsk. Built by design bureau OKB-10 on the popular KAUR satellite bus, the Sfera satellites were equipped with lights and radio transmitters similar to those on ANNA-1B. Operational flights ran from 1973 to 1980.

A similar difference was apparent in the case of satellites equipped with cameras for mapping, as opposed to high-resolution reconnaissance photography. A dedicated mapping satellite was among the planned elements of the first US reconnaissance satellite system, the Air Force’s SAMOS (or Satellite and Missile Observation System). That camera, the E-4, never flew, but the Army’s very similar project ARGON was grafted onto the CIA Corona program. ARGON was rendered obsolete by the inclusion of small mapping cameras on subsequent satellite systems but after ARGON’s first launch in 1961 – only one year after the very first US reconnaissance satellite – the US was never without a mapping capacity in orbit.

In the USSR, on the other hand, the first dedicated mapping satellite came quite late. The Zenit-4MT, program name Orion (11F629), was a variant of the main Soviet series of photo-reconnaissance satellites. First launched in 1971 and accepted into operational service in 1976, Orion began flying nine years after the first Soviet photo-reconnaissance satellite was launched. Unlike the Americans, who integrated mapping cameras into other photo-reconnaissance satellites, the Soviets seem to have continued to fly dedicated cartographic systems for the remainder of the Cold War (this is early 2000s information, so it may be obsolete now). Zenit-4MT (Orion) was followed in the early 1980s by the Yantar-1KFT, program name Siluet/Kometa (11F660), a system which combined the propulsion and instrument modules of the latest Soviet photo-reconnaissance satellite with the descent canister from the Zenit-4MT. Flying alongside Kometa was an upgraded Zenit, the Zenit-8, program name Oblik, an interim design introduced because of delays in the former.

I hope The Red Atlas or someone else can explain more about what was happening here, because it certainly looks like the Soviet Union was making very different decisions from the Americans when it came to satellite geodesy and cartography.

Source Notes: Information on Soviet satellites comes from a range of sources, much of it in the Journal of the British Interplanetary Society. For the Orion series, Philip S. Clark, “Orion: The First Soviet Cartographic Satellites,” JBIS vol. 54 (2001), pp. 417–23. For Siluet/Kometa, Philip S. Clark, “Classes of Soviet/Russian Photoreconnaissance Satellites,”JBIS vol. 54 (2001), pp. 344–650. On the launch of Sfera from Pleketsk, Bart Hendrickx,”Building a Rocket Base in the Taiga: The Early Years of the Plesetsk Launch Site (1955-1969) (Part 2),” JBIS vol. 66, Supplement 2 (2013), pp. 220 (and online). For the Markowitz moon camera, Steven J.  Dick, “Geodesy, Time, and the Markowitz Moon Camera Program: An Interwoven International Geophysical Year Story,” in Globalizing Polar Science: Reconsidering the International Polar and Geophysical Years, edited by Roger D. Launius, James Roger Fleming, and David H. DeVorkin (Palgrave Macmillan, 2010).

Stakes in the Sand: Surveying in the Gulf War

In 1990, US forces arrived in the Persian Gulf with a cornucopia of navigation technologies: not just GPS but also LORAN, TACAN, TERCOM (for cruise missiles), and inertial navigation systems which used laser, electrostatic, or mechanical gyroscopes, as well as old-fashioned manual tools like maps and compasses. So why were US surveyors heading off into the Saudi desert?

The surveyors were from the 30th Engineers Battalion (Topographic), which was deployed to provide map production and distribution, surveying, and terrain analysis services to the theatre. The survey platoon’s work was being done on behalf of the Corps and divisional artillery, which had their own particular navigational needs. Unlike fighter or helicopter pilots, field artillery gunners didn’t have the opportunity to see their targets and make last-minute adjustments to their own aim. Unlike bomber crews or cruise missiles, their fire missions were not planned well in advance using specialized materials. To provide precise positioning information to the guns, each artillery battalion in the Gulf was equipped with two Position and Azimuth Determining Systems (PADS), truck-mounted inertial navigation systems that keep an ongoing track of the unit’s positions. At the heart of the PADS was the standard US Navy inertial navigation system, the AN/ASN-92 Carrier Inertial Navigation System (CAINS).

Like all inertial navigation systems, PADS had a tendency to drift over time. That meant that it required regular refreshes using a pre-surveyed location, or control point. The initial specifications for PADS were to achieve a horizontal position accuracy of 20 meters over 6 hours and 220 kilometers. Actual horizontal accuracy seems to have been far better, more like 5 meters. One reason for the high accuracy was that, unlike an airplane, the vehicle carrying the PADS could come to a complete stop, during which the system detect and compensate for some of the errors by the accelerometers in the horizontal plane.

Unfortunately, the US had exactly one control point in Saudi Arabia, at Dharan airbase (Army Reserve historian John Brinkerhoff says this and several other point surveyed were done with “Doppler based methods.” I assume that means using the TRANSIT satellite system, which determined location on the basis of Doppler shift). Starting from that control point, the 30th’s surveyors extended a network of new control points northwards and westwards towards the Iraqi border. Conventional line-of-sight survey methods would have been too slow, but the surveyors had received four GPS receivers in 1989 and soon got more from the Engineer Topographic Laboratories to equip a follow-up team of surveyors. Eventually, their survey covered 10,000 square kilometers and included 95 control points. Relative GPS positioning took about two hours (according to Brinkerhoff) and offered accuracy to about 10 centimerers (compared to 17 meters for regular GPS use). Absolute positioning – done more rarely – required four hours of data collection and provided accuracy of 1–5 meters.

When the ground war began on 24 February 1991, the two survey teams tried to stay ahead of the artillery, which meant driving unescorted into the desert and marking new control points with steel pickets with reflectors (for daytime) and blinking lights (for night-time). Providing location data through headquarters was too slow, so the surveyors took to handing it directly to the artillery’s own surveyors or just tacking it to the pickets. By the ceasefire on March 1 they had surveyed all the way to 30 km west of Basra. Where the artillery outran the control points they used their own GPS receivers to make a “good enough” control point and reinitialized the battalion PADS there, so all the artillery batteries would at least share a common datum. One thing PADS could do and GPS couldn’t was provide directional information (azimuth), so units that outran their PADS capabilities had to use celestial observations or magnetic compasses to determine direction.

What the 30th Battalion and the artillery’s surveyors did in the Gulf was different enough from traditional survey methods that the some in the army already used a different phrase, “point positioning,” to describe it. In the 1968–1978 history for the Engineer Topographic Laboratories, which designed army surveying equipment, PADS was one of three surveying and land navigation instruments singled out as part of this new paradigm (the others were a a light gyroscope theodolite with the acronym SIAGL and the Analytical Photogrammetric Positioning System).

Brinkerhoff tells the story of the 30th’s surveyors as the meeting of the high and low tech, but the work really relied on a whole range of technology. Most of the GPS surveying was relative positioning that was anchored to previous Doppler surveying. Position and azimuth information was carried forward by inertial navigation, and the position of the firing battery was paired with target information from a forward observer equipped with GPS, an inertial navigation system, or a paper map or from aerial photography which could be interpreted using the aeroplane’s own navigation system or a photointerpreter’s tool like APPS. GPS surveying and navigation did not stay wrapped up with all these other navigational tools for long. The technology was flexible enough to be used in place of many of them. But in the early 1990s, GPS’s success was contingent on these other systems too.

Sources Notes: The story of the 30th and its surveyors appears in John Brinkerhoff’s monograph United States Army Reserve in Operation Desert Storm. Engineer Support at Echelons Above Corps: The 416th Engineer Command (printed in 1992). Further details appear in the Army Corps of Engineers history Supporting the Troops: The U.S. Army Corps of Engineers in the Persian Gulf War (1996) by Janet A. McDonnell and “The Topographic Challenge of DESERT SHIELD and DESERT STORM” by Edward J. Wright in the March 1992 issue of Military Review. Reflections on how the artillery used PADS and GPS in the Gulf come from the October 1991 issue of Field Artillery, a special issue on “Redlegs in the Gulf.” Technical details for PADS are from the ETL History Update, 1968–1978 by Edward C. Ezell (1979).

Map Overlap: Warsaw Pact vs. NATO Grids

The Charles Close Society hasn’t updated its topical list of articles on military mapping since I wrote about it in 2015, but there is a new article by John L. Cruickshank (“More on the UTM Grid system”) in Sheetlines 102 (April 2015) that is now freely available on the society’s website. The connection to Soviet mapping is that Cruickshank discusses how both NATO and the Warsaw Pact produced guides and maps to help their soldiers convert between their competing grid systems. Unlike latitude and longitude, a grid system assumes a flat surface.That’s good for simplifying calculations of distance and area, but means you have the problems of distortion that come with any map projection.

Both the Soviets and Americans based their standard grids on transverse Mercator projections that divided the globe up into narrow (6° wide) north-south strips, each with own projection. These were narrow enough not to be too badly distorted at the edges but still wide enough that artillery would rarely have to shoot from a grid location in one strip at a target in another (which required extra calculations to compensate for the difference in projections). The American system was called the Universal Transverse Mercator (or UTM; the grid itself was the Military Grid Reference System, or MGRS). The Soviet one was known, in the West at least, as the Gauß-Krüger grid.

In his article, Cruickshank reports that by 1961 East German intelligence was printing 1:200,000 military topographic maps that had both UTM and Soviet Gauß-Krüger grids. By 1985 a full series existed that ran all the way west to the English Channel. Rather than print a full map series with both grids, the US Army produced intelligence guides to the conversion between them. Field Manual 34-85, Conversion of Warsaw Pact Grids to UTM Grids was issued in September 1981. A supplement, G-K Conversion (Middle East) was released in February 1983. As Cruickshank observes, both manuals have fascinating illustrated covers. Conversion of Warsaw Pact Grids features a map with a rolled up map labelled “Intelligence” standing on a grid and looking at a globe focused on Europe. G-K Conversion, on the other hand, shows an Eagle literally stealing the map out of the hand of a Bear using calipers to measure distances from Turkey to Iran across the Caspian Sea.

The article ends with the observation that the history of modern geodesy, which underpins calculations like the UTM and Gauß-Krüger grids, remains “overdue for description.” Since it was published a new book has appeared that goes a long way towards covering some of those developments (at least for non-specialists, if not experts like Cruickshank). In fact, map grids are one of the main topics of After the Map: Cartography, Navigation and the Transformation of Territory in the Twentieth Century by William Rankin (University of Chicago Press, 2016). The book is chock-full of fascinating discussions of new mapping and navigation systems that developed between the end of the nineteenth century and the appearance of GPS. Its focus is on three overlapping case studies: large-scale global maps like the International Map of the World and World Aeronautical Charts (which have their own connection to Soviet mapping), grid systems like UTM, and radionavigation networks like Gee and Loran. (The third of these was already the topic of an article by Rankin that I wrote about here.)

In the chapters on map grids, After the Map shows just how long even an ostensibly universal design like UTM remained fragmented and regional. The use of grids had begun on the Western Front during the First World War. It spread to domestic surveying in the interwar period and been adopted by all the major powers during the Second World War. But universal adoption of the principles involved did not mean adoption of a common system. Even close allies like the United States and Britain ended up just dividing the world and jointly adopting one or the other nation’s approach in each region: British grids were applied to particular war zones and a more general American system used for the rest of the world. Neither used a transverse Mercator projection.

Even once America and its NATO allies settled on UTM as a postwar standard – a decision made despite opposition from the US Navy and Air Force, who fought vigorously for a graticule rather than a grid – UTM maps did not use a single consistent projection but adopted whichever reference ellipsoid was already in use for a region. While those differences were eventually resolved, even the 1990 edition of Defense Mapping Agency Technical Manual 8358.1, Datums, Ellipsoids, Grids, and Grid Reference Systems, still included specifications for twenty British grids including the British and Irish domestic surveys (plus a further nineteen further secondary grids), as well as the Russian Gauß-Krüger. East German tank commanders should have been grateful that they could get away with only two from the Intra-German Border to the Channel!

Smart Plane, Dumb Bombs, Bad Maps?: Part Two

Back to Part One

Designed around bleeding-edge 1960s avionics  the F-111 was built to would take the guesswork out of high speed, low-level navigation. Its avionics included an inertial navigation system (INS), terrain-following and attack radars, and a navigation computer that used these inputs to determine the airplane’s current location. Since an INS tends to drift over time, due to small errors in the measurements made by its gyros and accelerometers, the F-111’s navigator provided updates by taking a radar fix on a nearby landmark, usually known as an offset aimpoint, or OAP. Though they might be taken for granted by an observer, the entire process was dependent on good maps and geodetic information. F-111 pilot Richard Crandall’s description of Operation EL DORADO CANYON, the 1986 air attacks on Libya, explains what could go wrong when the F-111 flew with bad information.

Three groups of F-111Fs were involved in the operation, two equipped with laser-guided bombs (LGBs) and a third – attacking Tripoli airport – with “dumb” bombs that would be slowed by ballutes to allow for low-level delivery. All carried the PAVE TACK laser-designating pod, which also included an infra-red camera.

An F-111F aircraft releases Mark 82 bombs equipped with ballutes over a training range in 1986. Air Force photo via Wikimedia Commons

An F-111F aircraft releases Mark 82 bombs equipped with ballutes over a training range in 1986. Air Force photo via Wikimedia Commons.

Crandall focuses on the attack on Tripoli airport, where five aircraft carrying seventy-two bombs reached Tripoli airport but only one succesfully hit the Libyan aircraft parked on the tarmac. Why? According to Crandall, the attacking planes had been provided with the distance between a very visible radar target at the airport and where their bombs were supposed to land (“the radar offset”), and that information was wrong.

The aircrew that hit the airport, hats off to them! I knew the WSO extremely well, a good friend and fellow instructor for several years. In watching his tape, he nailed the radar offset for the airport. The radar was not good at burning out flat concrete but did much better on targets with more radar reflectivity. He went to narrow sector expand mode on the offset and then switched back to the Pave Tack infrared video, and nothing appeared. He went back and checked the offset again, and still dead on. The he switched back to the Pave Tack. Every other aircraft let the bombs fly using the radar offset. Their bombs hit the airfield between the taxiway and the runway. The coordinates on the offset were evidently bad. My friend went from narrow sector to wide sector in the Pave Tack and in the right side edge of the field of view he caught sight of the IL-76s. You hear him shout “come right come right” to the Pilot who is seeing nothing except tons of anti-aircraft artillery exploding and his TFR screen. The pilot made a hard turn. As he rolls out, his WSO has fired the lasers and the bombs immediately flew off. You see in the video the Pave Tack’s video rotate to upside down due to the mechanics of the pod rotating to see the target behind the aircraft. The WSOs had to learn how to track upside down when guiding LGBs. You then see a huge explosion rip through the airplanes. That was incredible teamwork in the cockpit. Good on the WSO to switch to wide field of view—it went from a really narrow straw to a slightly fatter straw to look through, but got him onto the target.

All the aircraft attacking the Tripoli area seem to have had trouble with navigational updates, not just those at the airport. The final update by radar OAP before crossing the Libyan coastline was the island of Lampedusa, and the aircrew were given coordinates for their OAP that were off by several hundred feet. James A. Jimenez, who flew one of the F-111s attacking Bab al-Aziziyah, wrote his recollections of the mission for the December 2008 issue of Air and Space Magzine. He remembers the last radar update point as being a tower at the western tip of Lampedusa.

Our navigation system had been running sweet, but when Mike [his WSO] selected the tower, the cursors fell about one mile to the west. An error during the planning process had resulted in incorrect coordinates being issued to all crews. Mike recognized the error and did not use the coordinates to update our navigation system. His decision was probably the single greatest factor enabling us to hit our target: those who updated their nav systems based on the bad coordinates missed.

Among those who ran into trouble was one F-111 targeting the Bab al-Aziziyah barracks whose error at Lampedusa was compounded upon reaching Tripoli and which ended up a mile and half off target. Its bombs ended up hitting and damaging the French embassy.

I’m still not entirely clear on where the offset coordinates for EL DORADO CANYON came from. According to an official US Air Force history, during the F-111s first combat deployments to Vietnam the offset aiming points came from a photo-positioning database called SENTINEL DATE at the Defense Mapping Agency Aerospace Center in St. Louis, or an equivalent database called SENTINEL LOCK that was deployed to Takhli and Nakhon Phanom air force bases in Thailand. SENTINEL DATE/LOCK “provide[d] a menthod for precisely determing the latitude, longitude, and elevation of navigational fix-points, offset aim points, and targets.”

However, a student paper for Air Command and Staff College by Major James M. Giesken explains that the update points for EL DORADO CANYON were geolocated by the F-111 fighter wing staff using the Analytical Photogrammetric Positioning System (APPS), an analog system for determing the location of an object on photo imagery. APPS’s output used the WGS 84 standard datum, while the target coordinates were expressed in the European Datum used by American units in Europe, and this was the source of the location error. (There’s no source for that information in the paper, but Giesken was an instructor at the Defense Mapping School from 1986 to 1988, then aide to the director of the Defense Mapping Agency for fourteen months and executive officer for the director for another seventeen. Hopefully he had a good source for the information.)

The Analytical Photogrammetric Positioning System. From Army Research & Development, May-June 1976, p.24

An early version of the Analytical Photogrammetric Positioning System. From Army Research & Development, May-June 1976, p.24

What happened during Operation EL DORADO CANYON demonstrated the obstacles to accuracy that could not be erased by the use of advanced technology, whether in a bomb or an airplane. Regardless of the precision in the weapon, an attack was only as accurate as the underlying information – and problems with that information could end up embedded in the relationships between the very systems that were supposed to provide a more precise attack than ever before.

A Hidden Map Between Sensor and Shooter: The Point Positioning Data Base, Part Three

Back to Part Two (or Part One)

Between 1990, when the first GPS-guided missiles were used in war, and 2001, when the United States began its invasion of Afghanistan, GPS guidance for weapons went from a niche technology used only by a few systems to one of the US military’s favorite techniques. The spread of GPS guidance led to a huge demand for ways of determining target positions in a way that weapons – rather than pilots – would understand. That meant three-dimensional coordinates in World Geodetic System 84 (WGS 84), rather than grid references on maps or even coordinates in other datums. One of the most important tools for establishing these coordinates was the Point Positioning Data Base (PPDB), a database of matching imagery and coordinates that had originated in the 1970s as a tool for army field artillery.

Made widely available in an analog format in the 1980s and used during the first Gulf War, PPDB’s digitization had restricted its use mostly to computer workstations (first DEWDROP, then RainDrop) in the United States during the war over Kosovo in 1999.

By the time the invasion of Afghanistan began in late 2001, RainDrop workstations had moved from analysts’ desks in the continental US to the same airbase – Prince Sultan Air Base in Saudi Arabia – as the air operations center that was commanding the air war. That shift was only the first step in the proliferation of tools and services for point mensuration to match the American and coalition demand for mensurated target coordinates. “Cursor on Target” (see Part One) began development in 2002; Northrop Grumman released RainDrop’s successor – RainStorm – in 2004; and another system, Precision Strike Suite for Special Operations Forces (PSS-SOF), was created to provide “near-mensurated” coordinates to troops in the field.

By 2009, when Noah Shachtman wrote a description of how mensuration was used to plan air strikes in Afghanistan, the process had been in regular use for almost a decade. Here’s his description of what was being done in the air operations center for Afghanistan:

An officer, I’ll call him Paul, walks me through the process. It starts with “targeteering,” figuring out where a pilot should attack. Just getting GPS coordinates or an overhead image isn’t good enough. GPS is unreliable when it comes to altitude. And landscape and weather conditions can throw satellite pictures off by as much as 500 feet. “Even with Gucci imagery, there’s always errors,” Paul says. He points to a pair of screens: On the right side is an aerial image of a building. On the left, two satellite pictures of the same place — taken from slightly different angles — flicker in a blur. Paul hands me a pair of gold-rimmed aviator glasses. I put them on, and those flickers turn into a single 3-D image. Paul compares the 2-D and 3-D images, then picks exactly where the building should be hit. Depending on elevation, adding a third dimension can shrink a 500-foot margin of error down to 15 feet.

Tying a point on the ground to a global grid precise enough to be used for air strikes anywhere in the world was now a matter of course. Fifty years after the CIA’s photo interpreters bought their first mainframe to help them analyze and map targets in the Soviet Union, calculating a target’s position in global terms has become simple – even if knowing what is at the target location is not. The technology here is also a long way from the cobbled-together equipment for which the PPDB was first created. The Analytical Photogrammetric Positioning System (APPS) combined digital and analog electrical components with old-fashioned optics and the human eye.

The transformation from APPS to RainStorm over the course of thirty years is pretty remarkable, but its also been hard to track. This is technology that doesn’t get a lot of praise or get singled out for attention, but that doesn’t mean its not interesting or important.

For one thing, APPS was a military application of commercial off-the-shelf (COTS) technology before COTS was cool. The Hewlett Packard 9810A desk calculator at its heart was not designed for military use or developed from military-sponsored research. It was just an office tool that was re-purposed for a very different office.

More importantly, APPS and PPDB are a good example of an enabling technology that was created long before its eventual requirement even existed. If there had been no PPDB, the development of GPS-guided bombs would have forced its creation. Instead, it was an Army project begun around the same time the first GPS satellites were being designed that provided the necessary service. That’s luck, not good planning.

Lastly, and equally interestingly, PPDB is a layer of complexity in modern warfare that’s easily overlooked because it sits in the middle of things. It provides the map of coordinates on which grander, more significant, moves are sketched, and which disappears into obscurity except when something goes wrong. Between cursor and target, or sensor and shooter, there are a lot of layers like this one.

A Hidden Map Between Sensor and Shooter: The Point Positioning Data Base, Part Two

Back to Part One

One part of the long pre-history surrounding the deployment of GPS-guided bombs began in the late 1960s with US Army Corps of Engineers and a research project to improve the accuracy of American field artillery. The Analytical Photogrammetric Positioning System (APPS) was a tool to calculate the coordinates of a target seen on reconnaissance photography. Introduced into service in the mid-1970, APPS and the geo-referenced imagery that it used (the Point Positioning Data Base, or PPDB) proved so useful that they were borrowed by US Air Force and Navy airstrike planners too.

The desire to fix targets from aerial photography and strike them with precision was hardly unique to APPS’s users. The Air Force also had a system for calculating target coordinates under development. The Photogrammetric Target System (PTS) was part of a far grander system for detecting, locating, and destroying enemy surface-to-air missile (SAM) sites called the Precision Location and Strike System (PLSS). Unlike APPS, which printed out target coordinates for human use, the proposed PTS was a fully computerized system that would transmit the coordinates to PLSS’s central computer somewhere in West Germany or the United Kingdom, where they would be converted into guidance instructions for the 2,000-lb glide bombs that were going to be the sharp end of the system.

The TR-1, a renamed U-2 reconnaissance plane, was the aerial platform for the PLSS system. (U.S. Air Force Photo by Master Sgt. Rose Reynolds)

The TR-1, a renamed U-2 reconnaissance plane, was the aerial platform for the PLSS system. (U.S. Air Force Photo by Master Sgt. Rose Reynolds)

You can see how PTS’s fortunes waxed and waned by following the annual briefings on PLSS that the Air Force gave to Congress. What began in 1973 was gradually scaled back as PLSS’s own funding declined. Plans for a manual prototype PTS were cancelled when it became clear that APPS could do the same job, and the system disappeared from the briefing in 1980.

Much of the imagery for point positioning came from mapping cameras on the KH-9 HEXAGON satellite. NRO photograph courtesy Wikimedia.

Much of the imagery for point positioning came from mapping cameras on the KH-9 HEXAGON satellite. NRO photograph courtesy Wikimedia.

While the Air Force was experimenting with PTS and APPS to plan aerial attacks, PPDB was expanding in importance to become part of the targeting process for non-nuclear Tomahawk missiles being operated by the US Navy. Simultaneously, crises with Iran and the demands of the Carter Doctrine drove the expansion of PPDB coverage in the Middle East to 930,000 square nautical miles by 1981.

That meant that when Iraq invaded Kuwait in 1990 the US had 100% PPDB coverage of the theater, better than the coverage with either 1:50,000 topographical maps or 1;250,000 Joint Operations Graphic-Air. Unfortunately, the PPDB imagery was woefully out of date, forcing the Defense Mapping Agency (DMA) to make PPDB updates part of its vast cartographic build-up for Operation Desert Shield. That included 30 new PPDB sets (of 83 requested), 26 video PPDB sets, and 7,972 target coordinates.

Despite those deliveries, the obsolescence of PPDB imagery was noticed during Operation Desert Storm. The annual official history of 37th Fighter Wing – which flew the F-117 stealth fighter during Desert Storm – complained that:

Spot imagery was not of sufficient high resolution to support the technical requirements of a high technology system such as the F-117A Stealth Fighter. And, the available Analytical Photogrammetric Positioning System (APPS) Point Positioning Data Base (PPDB) was grossly outdated. It was not until the last week of the war that more current PPDBs arrived, which was too late to have an effect on combat operations.

After 1991, the need for precise target coordinates grew alongside the spread of precision guided weapons that needed those coordinates, which meant that what had begun as an Army instrument became more and more vital to aviation. A 1994 naval aviation handbook reminded users that “reliable target coordinates come only from a limited number of classified sources,” including the Defense Mapping Agency’s “Points Program” (which accepted requests by phone or secure fax) and APPS systems carried on aircraft carriers.

Unlike laser or electro-optical-guided bombs that homed in on a signature that their target emitted or reflected, bombs and missiles guided by GPS simply fly or fall towards the coordinates they are given. Widespread deployment during the bombing of Serbia in 1999 (Operation ALLIED FORCE) therefore meant a vast demand for precise target coordinates.

The Point Positioning Data Base, now provided in digital form rather than as a film chip/magnetic cassette combination, was an important source of those coordinates because it provided not just two-dimension latitude/longitude coordinates but also elevation. In a desert environment like Iraq, a bomb dropped from above could more or less be assumed to hit its target no matter how large the gap between the actual elevation of the ground. Where the terrain was more varied, however, aiming to high or too low could cause the bomb to slam into a hill short of the target or fly right over it and land long. Securing that elevation information from aerial photography was known as “mensuration.”

Though APPS was a computerized tool, it used film chips rather than digital imagery. To take the entire system digital, the National Imagery and Mapping Agency (which had absorbed the Defense Mapping Agency in 1996) developed a computer workstation called DEWDROP that could provide mensurated coordinates using the Point Positioning Data Base. That was followed a few years later by a similar system called RainDrop. In February 1999, a little over a month before ALLIED FORCE began, the Air Force committed to buy 170 RainDrop systems for $1.8 million from Computek Research, Inc. (Here’s the press release.)

During ALLIED FORCE, mensurated coordinates were needed for Tomahawk, CALCM, and SLAM missiles, as well as the JDAM bombs being carried by the first B-2 stealth bombers. To get them, the air operations center in Vincenza, Italy had to reach back to analysts in the United States, which was where the mensuration workstations were located. Here’s how Vice Admiral Daniel J. Murphy, Jr. describes the process of acquiring them, starting from a rough fix provided by an ELINT satellite:

So I walked into the intelligence center and sitting there was a 22-year-old intelligence specialist who was talking to Beale Air Force Base via secure telephone and Beale Air Force Base was driving a U–2 over the top of this spot. The U–2 snapped the picture, fed it back to Beale Air Force base where that young sergeant to my young petty officer said, we have got it, we have confirmation. I called Admiral Ellis, he called General Clark, and about 15 minutes later we had three Tomahawk missiles en route and we destroyed those three radars.

About a year later the Air Force ordered another 124 RainDrop systems. (Another press release.) Three months later, Northrop Grumman bought Computek for $155 million in stock.

ALLIED FORCE was confirmation for many observers that coordinate-guided weapons were the wave of the future. Tools like PPDB were necessary infrastructure for that transformation.

Forward to Part Three