Tag Archives: aerial photography

Ted Abrams

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Yesterday the December issue of American Surveyor magazine appeared in my mailbox. American Surveyor is one of the few trade publications I read from cover-to-cover every month, and it’s one of the very few I’d gladly pay a subscription fee for. But since the publisher, Cheves Media, provides it free of charge all the better.

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This month’s issue hits it out of the ballpark. The cover is one heck of a teaser – a beautiful shot of the John Bird transit telescope used by surveyors Charles Mason and Jeremiah Dixon to establish the boundary between Pennsylvania and Maryland just before the Revolutionary War. This is the famous ‘Mason – Dixon line’ that today is viewed (incorrectly) as the cultural and political dividing line between the American North and South. Mason & Dixon’s achievement is an important topic in the history of topography in the Americas and we’ll have more on it in a later post.

Today however we’ll focus on the other key article in the magazine – a short overview of the achievements of Ted (Talbert) Abrams, an early pioneer in the science of photomapping and and photogrammetry. Abrams was one of the quiet heroes of topographic history, someone most have never heard about but who’s accomplishments revolutionized science, established an industry and helped found the geospatial profession many of us practice in today.

Ted Abrams

Just what were Ted Abrams’ achievements? He effectively invented the business of photomapping. It was his experience as a US Marine Corps reconnaissance pilot during WWI that convinced him that aerial photography could be used to make highly accurate maps. At the time traditional mapping technology required the use of ground survey and field verification crews to literally walk and survey the areas to be mapped, usually using laborious plane table survey methods. The process was slow and expensive. One of the earliest uses of aircraft during WWI was to take vertical photos of battlefields for the creation of map substitutes. These were simple photo mosaics annotated with things like road and town names, but they filled a critical need.

Coming out of the war Abrams was convinced that photomapping could not just be a viable business, but could revolutionize the science of large scale mapping over broad areas. Ted Abrams was part pilot, part scientist and part entrepreneur, and all genius. Where no industry existed, he developed the techniques and the instruments necessary to capture and process tightly controlled areal mapping photography and compile accurate maps from that data. He then developed the business model that made it all profitable. He also helped develop a lot of the science behind the processes involved in photomapping. You can’t claim your maps and photo mosaics are accurate unless you can prove the mathematics and geometry that went in to making them, and Abrams was an early pioneer in developing the mathematical principles behind processes like aerotriangulation.

 

Ted Abrams was also a life-long patriot and a proud Leatherneck. During WWII he set up schools that trained thousands of Marine Corps photo mapping and photo analysis specialists, and his techniques and textbooks were in wide use across all the military services. One of his simplest yet greatest accomplishments was the invention of  the folding pocket stereoscope. This stereoscope was manufactured by the hundreds of thousands by the Abrams Instrument Corporation and other manufacturers and became the indispensable tool of photo interpreters, surveyors, cartographers and intelligence analysts around the world.

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Invented by Ted Abrams in 1942, the simple folding pocket stereoscope has been the indispensable tool of topographers for over 70 years. They are still in wide use today

After the war Abrams’ business flourished as America went on a building boom. He built Abrams Aerial Survey into the leading aerial survey firm in the United States and the Abrams Instrument Corporation became a leading supplier of aerial photography, photogrammetry and aerial photo analysis instruments.

Ted Abrams was a founding member of the American Society of Photogrammetry (now the American Society of Photogrammetry and Remote Sensing (ASPRS)) and much of his pioneering work made its way into the first editions of the industry’s standard reference, the Manual of Photogrammetry.

Manual of Photogrammetry

In recognition of Abrams’ contributions the ASPRS presents the Talbert Abrams Award every year to ‘encourage the authorship and recording of current, historical, engineering, and scientific developments in photogrammetry.’

One last example of Ted Abrams’ genius. He came out of WWI with a clear understanding of the limitations of current aircraft designs when used as platforms for aerial cameras. Abrams knew he needed a more stable aerial survey platform designed around the needs of the camera system and crew. In the 1930’s Abrams sat down and designed what became the world’s first dedicated aerial imagery platform – the Abrams P-1 Explorer.

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First flown in 1938, it was specifically designed for the mission of acquiring aerial mapping photography. The P-1 incorporated a number of unique design elements, including a pusher-type engine arrangement designed to keep leaking oil and fluids from smearing the camera lenses (a serious problem with conventionally laid out aircraft using rotary engines), and it was one of the earliest aircraft to utilize Plexiglas for windows. In fact the nose layout made its way into WWII military aircraft designs, particularly the nose arrangement of the early B-24 Liberators.

Unfortunately the P-1 design was a victim of war. By the time the aircraft became operational proved itself as an outstanding aerial camera platform WWII had broken out. The US Army Air Corps looked at the design and deemed it too slow and too vulnerable to enemy fire. Ted Abrams realized he needed to work on ways to mount mapping camera systems in fast moving fighters and modified bomber aircraft and threw himself into the task without looking back. Only one model of the P-1 was ever built and it remained in operation in the US until 1948.

 

A fascinating aircraft designed by a true genius and pioneer in our industry. We truly do stand on the shoulders of giants.

Brian

It’s Throwback Thursday!

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Everybody does ‘throwback Thursday’ these days, so why not me.

I came across these quirky but interesting (for a topo geek and an airplane geek) video clips on YouTube and thought I’d share them.

First, a nod to our Air Force friends. From WWII right on through the 1980s the Army Topographic services relied on the US Air Force for wide-area mapping photography support. The Army did pick up some missions using its fixed-wing intel platforms like the venerable Grumman OV-1 Mohawk, but for the most part it was the Air Force (or the Air Force Reserves or Air National Guard) who handled the military requirements for mapping photography. You can read more about the USAF’s photomapping activities at the 1370th Photomapping Squadron’s history site. In fact, as late as 1994 in Panama we were tasking the Air Force to fly Furbish Breeze photo reconnaissance missions over key areas of Ecuador and Peru for cartographic map updates and terrain study development. Furbish Breeze wasn’t a mapping camera system, but it was the best we had available at the time and the Air Force was happy to fly for us.

Let’s start with 1961 and British Guiana. This looks like a home movie shot without sound and it depicts the mundane routine of supporting photomapping missions in British Guiana (today’s Belize). I’m guessing this mission was being run in support of the IAGS. This is the 1370th Squadron in action:

Next, let’s move to Vietnam. Here’s a video showing 1370th operations out of Tuy Hoa Airbase in South Vietnam in 1968. The Army Topographic services had a huge mapping mission in Vietnam – most of the original mapping of the country had been done by the French pre-WWII and was badly outdated by the time US forces got heavily involved in the conflict. Army Topographic units had to re-map the entire country at all scales, and had to do it fast. We relied very heavily on mapping photography provided by the 1370th:

Honestly I have little or no idea what these guys are doing inside the aircraft during flight. I get the general idea that they are checking in with HIRAN ground stations and monitoring camera operations, but that’s about it. If there are any USAF photomapping veterans out there who’d like to provide some insight into what’s going on in the videos please chime in!

Next, it’s something for the Squids (sorry, I couldn’t resist). These videos don’t depict mapping or charting activities, but they are interesting snapshots of photo intelligence activities.

The first video is a short clip showing what I assume is a photo interpretation team aboard an aircraft carrier reviewing stereo photos during WWII:

Next is a formally produced video made during WWII showing the importance of aerial photo reconnaissance in the Pacific Theater. Beyond the ‘mom & pop homefront’ scenes at the beginning and end of the video it’s actually pretty good. And hang in to the end to see Navy Commander R.S. Quackenbush discussing the importance of photo reconnaissance and take note of the stereoscopes and aerial photography neatly arrayed on his desk for dramatic emphasis:

Thanks for watching!

– Brian

The Frost Course

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…or how I learned to live on coffee and Tylenol for two weeks.

In the military there are certain rights of passage, like your graduation parade at the end of basic training, or making your fifth parachute jump and getting your silver parachutist wings, or getting your butt chewed by the First Sergeant for showing up late for formation, or going down to Yadkin Road and getting your first tattoo (you old Fort Bragg veterans will know what I’m talking about).

In my old field, terrain analysis, one of the rights of passage was successfully completing the Frost Course. No, the Frost Course didn’t have anything to do with the weather, and it wasn’t a poetry reading class. The Frost Course was considered a master class in the use of stereo aerial photography for landform analysis and military terrain analysis.

The course was developed by Dr. Robert E. Frost while working for the US Army’s Engineer Topographic Laboratories (ETL) where he headed up ETL’s Center for Remote Sensing.

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As I once heard Dr. Frost explain it, the analyitical techniques taught in the course were developed over several decades of research based on aerial photo analysis in support of a wide variety of military and civil projects for the Army Corps of Engineers. His work dated all the way back to WWII and Purdue University, where he pioneered many of the aerial photo pattern analysis and terrain analysis techniques that would become the backbone of later Army terrain analysis training.

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Dr. Frost began his career at Purdue University, where pioneering research in the use of aerial photography for terrain and resources analysis began in the late 1920’s.  Frost worked at Purdue with both Professor Bushnell and another aerial photo analysis pioneer, Dr. Donald Belcher before moving over to the Army Corps of Engineers

 

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During WWII the Army Corps of Engineers vastly expanded the use of aerial photography for mapping and terrain analysis. This demand was triggered by pioneering work done in the 1935 – 1941 time period by both Army topographic engineers and researchers at places like Purdue University who developed the aerial camera systems and analytical processes and tools needed to exploit this new resource

Dr. Frost noted that he expanded this work into historical terrain analysis while acting as an expert witness in a string of court cases brought against the Corps of Engineers. Starting in the 1970’s the Corps of Engineers became a favorite target of the environmental movement. The Corps was an easy mark. It was involved in billions of dollars of public works projects across the United States, most involving waterways improvements. In mid-20th century parlance ‘improvements’ mean draining wetlands, building dams and levees, dredging rivers and digging canals. A favorite joke of the day went like this: “Why don’t Corps of Engineer officers help their wives with the dinner dishes? Because they can’t stand the sight of running water!”

At some point the Corps of Engineers turned to Dr. Frost to see if he could develop evidence to prove that Corps projects were not responsible for the impacts the plaintiffs were seeking damages for. Dr. Frost figured the best way to approach the problem was to look at the history of the project areas as shown in successive years of aerial photography and try to determine the what was causing the issues the land owners and environmentalists were so upset about. Dr. Frost and his team at the Center for Remote Sensing went through the vast aerial photo archives of the the USGS, NOAA, the Soil Conservation Service, the Department of Agriculture, the Tennessee Valley Authority, state and local agencies, private aerial survey companies and even the Corps of Engineers’ own holdings to build a library of historical aerial photography covering various Corps’ project areas. Much of this photography went back into the 1930’s and predated by decades the projects that were in dispute.

Dr. Frost’s team then applied the aerial photo analysis techniques developed over decades of research and field study to establish a terrain analysis ‘timeline’ of the changes that took place over the project areas. More often than not Dr. Frost and his team were able to prove that the Corps of Engineers’ activities were not the proximate cause of the issue. Things like historical land use changes, flood and drought cycles, poor erosion control, poor land management practices or other human or environmental impacts that had nothing to do with the Corps’ activities were frequently identified as the root cause of the problem.

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OK, who’s gonna’ pay?

In the late 1970’s the Army recognized the growing demand for terrain analysis products needed to support military planning and operations. The decision was made to establish Engineer terrain analysis teams at the division, corps and echelons above corps levels. The analysis processes the Soldiers in these units used were based on techniques developed by ETL’s Terrain Analysis Center. Dr. Frost and the Center for Remote Sensing were key resources the Terrain Analysis Center turned to for help developing the aerial photo analysis techniques that needed to be taught to the hundreds of enlisted analysts and warrant officer candidates that would make up these new terrain analysis teams.

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Germany 1985. Soldiers of the 517th Engineer Detachment (Terrain Analysis) use a zoom transfer scope (ZTS) to create terrain overlays using aerial photography. The study was done to support the V Corps REFORGER 85 exercise. The overlay will depict soil types that are least able to support off-road vehicle traffic. The techniques used to analyze the imagery were developed by Dr. Frost and his team at the ETL Center for Remote Sensing and the ETL Terrain Analysis Center. CW2 Tim Butler, the detachment’s terrain analysis technician and an early graduate of the Frost Course, is at the ZTS

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The resulting analysis for REFORGER 85 was used daily to predict areas at high risk for maneuver damage based on soil type, moisture content and ground temperature.  After the exercise V Corps announced that this analysis saved an estimated $1 million dollars in maneuver damage claims compared to previous REFORGERs

At some point Dr. Frost decided to package his experience and analysis techniques as a formal class, and the Frost Course was born. This course took the elementary photo analysis processes taught in the terrain analysis classes at the Defense Mapping School and expanded them to cover a wide range of topics beyond military applications, adding course content in geology, soils science, forestry, agriculture, hydrology, transportation and urban analysis. Woven into the course were college-level requirements in analysis, research and thesis defense.  It was a master class in aerial photo analysis for topographic and terrain analysis.

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Dr. Frost’s ‘Statement of Principles’ for the Frost Course

Starting in the early 1980s Dr. Frost taught his class regularly at the Defense Mapping School (DMS) at Fort Belvoir, VA. Unlike so much US Army military training at the time the Frost Course was actually challenging; Dr. Frost forced you to analyze and think. There were no multiple choice questions in his course. You discussed a particular terrain issue, reviewed applicable analytical techniques, were presented with a problem, sent off to do the analysis and then came back to present your results and defend your conclusions. While you couldn’t actually fail the Frost Course, the competition to get into the class was so tough that only highly motivated Soldiers attended, so the quality of the output – skilled terrain and topographic analysts – was quite high.

The Frost Course was taught in modules (called ‘Problems’), with each module teaching a particular analytical process based on things like landform, pattern, hydrological, transportation or urban analysis. Each module consisted of some instructional material, references, an assignment sheet and a set of stereo aerial photos.

Frost Course Module 3

Frost Course Problem 3, Pattern Recognition

 

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Problem 3 required detailed analysis of a stereo triplet to determine the landforms, drainage, vegetation, cultural and land use patterns. These are current photos taken of the coursework I completed in 1995.

The joke was that when you showed up for the Frost Course you got issued two things – a pocket stereoscope and large bottle of Tylenol. That’s because you spent 6 hours each day in class staring at stereo photos and then you went home and spent another couple of hours peering through the stereoscope as you worked on your homework assignment. Headaches due to eye strain were the norm.

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Frost Course, Day 1 – eyestrain is starting to set in…

I met Dr. Frost back in 1982 when he visited us at Fort Bragg. The Engineer Topographic Laboratories (ETL) sent him to pitch the idea of having him teach his class at Fort Bragg. The Army had a growing demand for terrain analysts and DMS couldn’t train them fast enough. The idea was that the Frost Course would enhance the skills of the terrain analysts already assigned to Fort Bragg, provide a good foundation of skills for those Engineer Soldiers interested in becoming terrain analysts and provide additional training to a number of photo interpretation analysts from the Intelligence units on Fort Bragg. It was far cheaper to bring Dr. Frost to the students than it was to send the students to Dr. Frost. Sadly, the senior Engineer commanders on Fort Bragg disagreed and the idea was nixed. The XVIII Airborne Corps Assistant Corps Engineer at the time commented, “Why should we pay for training these guys (terrain analysts) already get when they go to DMS?” Obviously this idiot wasn’t listening when Dr. Frost clearly and concisely laid out the differences between what our terrain analysts learned in their basic classes at DMS and what his course provided.

Over the next decade I sent dozens of Soldiers from my units to the Frost Course at DMS. While many of my battalion and brigade commanders questioned the value of the course I knew that the Soldiers would come back better analysts. Being selected to attend was viewed as recognition that a Soldier was ‘on his (or her) way’; headed for greater rank and responsibility. I even used attendance at the Frost Course as a reenlistment incentive – “Pssst – hey Specialist Jones, sigh up for another three years and I’ll get you a seat in the next class.” It was surprising the number of Soldiers who took the offer.

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Another Soldier, SPC Cantu, reenlists for the Frost Course. In this case I was even able to wrangle him an assignment to the Topographic Engineering Center. He still owes me a beer

But I never got to take the course from Dr. Frost. I would send Soldiers at the drop of a hat but my superiors never seemed to think it important that I attend. Dr. Frost retired in 1990 but before he left he handed responsibility for teaching and updating the class over to Major John Jens, who worked at the Topographic Engineering Center (the successor to ETL) at Fort Belvoir. In 1995 I was sent to the Defense Mapping School for my Warrant Officer Advanced Course. Since only two of us showed up for the Advanced Course that year the course coordinator had little for us to do. We were supposed to work on a nebulous ‘research paper’ but that was it. I could have wandered the hallways and counted floor tiles for a month and still graduated at the top of my class. One day right after I arrived I picked up a DMS course catalog and saw that John Jens (now retired) was scheduled to teach the Frost Course the next week. I looked over at the course coordinator and said, “I’ve never been through the Frost Course. I think I’ll sit in on it.” “Sure,” he replied “sounds like a good idea.” He went back to his Washington Post crossword puzzle relieved that he wouldn’t have to babysit me for another few weeks.

A month ago I was going through some old Army paperwork and unearthed all of the Frost Course modules I worked on in John Jens’ class back in 1995. Looking through the aerial photos and study papers triggered a wave of nostalgia and caused me to write this post. But more to the point, since 1995 I’ve had literally hundreds of hours of additional education and training in terrain analysis, geospatial analysis, graduate level work in geography, geodesy and surveying and a broad range of industry specific geospatial software training. I can honestly say that nothing I’ve been taught since 1995 has approached the analytical rigor that the Frost Course demanded. It was (and hopefully still is) that good.

– Brian

Thinking in 3D

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This week at work, just for fun, I set up a stereoscope and slid some stereo photos underneath the mirrors. These photos are high resolution, large scale shots taken back in April when we had a new orthorectified aerial image of the airport developed.  I asked the contractor to send me a stereo pair from the project that I could play around with.  It’s been years since I spent any time peering though the optics of a stereoscope and it was fun to look over the images and realize just how much a stereo view adds to one’s ability to pick out details.

There was a time when analyzing stereo images was a critical skill in my field and other related fields.  But with the rise of commercial satellite imagery, the slow demise of wet process aerial film cameras and the development of digital imagery analysis systems like ERDAS Imagine and ESRI’s improved raster management routines in ArcGIS there has been less and less call for hard copy stereo image analysis. Software routines now handle most analysis tasks.  Of course photogrammetrists still process, manage and analyze stereo imagery, but it’s all done on high end digital systems these days.  The fields that used to derive benefit from hard copy stereo imagery – topography, geology, forestry, hydrology, even the US military – all seem to have lost their institutional ‘feel’ for the usefulness of stereo imagery analysis.

The issue was brought home to me this week when I invited a small group of GIS professionals and Engineering staff (both licensed civil engineers and engineering technicians) to drop by my desk to have a look at these stereo photos.  Most could not get the photos properly aligned underneath the stereoscope. Few recognized any real benefit from seeing the structures in stereo.  Most thought it was just a cute parlor trick. That’s a shame because the stereo photos permitted quick and easy identification of features that are not readily apparent in the same 2D images.  Things like antenna masts and raised utility piping on the roofs of concourses, raised concrete pads and curbing in the aircraft gate areas and even small assemblies like receiver domes on the tops of aircraft fuselages stood out in clear detail when viewed in stereo.
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So how does one use stereo photos for analysis?  Check out this blog posting from a while back.

Conducting stereo analysis using hard copy photos should be much cheaper and easier these days.  Years ago in the era of wet process film cameras making copies of stereo photos was time consuming and expensive. Someone had to pull a roll of film negatives, go into a darkroom and make prints one by one. With today’s digital imagery systems all one has to do is download the image files from a server and print them out using relatively cheap but very high quality color ink jet printers.  The images I received from our contractor were full resolution TIFF files, each about 1.4 gigabytes.  I was able to subset just the areas I wanted to view and print them out at full resolution using only the image management software that comes with Windows 8.  Fast and cheap!

Federal and state governments are sitting on a gold mine of historical stereo aerial photos.  The Federal government (USGS, USC&GS, Soil Conservation Service, Department of Agriculture, Tennessee Valley Authority, Army Corps of Engineers, etc.) started using stereo aerial photography for mapping as early as the mid-1920s and over the course of the next 90 years proceeded to photograph virtually all of the United States in stereo.  Stereo aerial photography was the foundation of all of our topographic mapping activities through most of the 20th century and it remains so today.  Much of this photography is still held in individual agency archives or has been turned over to the National Archives. I’d love to see the National Archives digitize and post nationally significant stereo pairs of images online for downloading and viewing. Places like the Grand Canyon, Yosemite and Yellowstone or historic events like the Mount St. Helens post-eruption photos or levee breaches along the Mississippi River during the spring floods.  Even historic shots of our cities and suburbs that will help students understand how topography impacts issues like urban sprawl.

Humans view and relate to their world in three dimensions.  It’s a shame that today we are relegated to investigating it via boring 2D computer displays.  I think it’s time to bring back 3D image analysis!