Right Under My Nose The Whole Time

As many of you know, I've been scratching around for some time trying to dig up the origins of the Military Grid Reference System (MGRS). I recently became interested in it in light of the fact that the US Geological Survey and Department of Homeland Security have adopted MGRS as the grid standard for the continental US (they're only 60 years late, but who's counting!).

I had some old friends at Fort Bragg who are involved in the mapping & charting field root around and they came back with the opinion that development of MGRS was likely tied to NATO and NATO standard agreements (STANAGs as we used to call them). There is probably some truth to that, but there were still several pieces of the puzzle missing. One of those was just when the US Army adopted MGRS.

For the past several months I've been scouring eBay, purchasing early copies of US Army map reading and land navigation manuals. The first official, general issue map reading manual came out in 1938 (Basic Field Manual Volume 1, Chapter 5, Map and Aerial Photograph Reading) and was quickly followed by updates in 1941 and 1944 as FM 21-25.

Tucked away in the back of my 1944 copy of FM 21-25, Elementary Map and Aerial Photograph Reading were two changes that I never paid much attention to. 'Changes' in Army parlance were updates to manuals or other documents. The Army would publish a change in the form of an addendum and distribute it throughout the Army. It was the individual unit's job to make sure all the changes were 'posted' (this usually meant you physically attached the change document to the base document by some means, like stapling). That's how the military managed publication changes before this internet thingey came along.

Today I was giving this manual a close read and decided to pay attention to the change documents. To my surprise one of the changes (Change 2) was dated November 1950 and was summarized as follows:

"Principal changes are in methods of giving grid references. These changes are made to comply with AGAO-S 061.3 (28 Dec 49) CSGID-M, dated 29 December 1949, which establishes the MILITARY GRID REFERENCE SYSTEM as official for the Department of the Army"

So there you have it. The Army adopted MGRS in December 1949. Part of the mystery solved!

So now I know the why and the when. What's still missing is the how.

MGRS is based on the Universal Transverse Mercator Grid (UTM), which was developed by the Army Map Service sometime right after WWII.  What I need to find now is the original description of UTM and MGRS, the document prepared by the Army Map Service describing how MGRS is calculated and constructed, and how it should be implemented.

My guess is that these founding documents are buried deep in the archives of the National Geospatial-Intelligence Agency (the descendant of the Army Map Service).

Anybody know someone at NGA who can spend a lunch hour digging around for this info?

Brian

Inter-American Geodetic Survey

NOTE: This is an older version of my posting on the IAGS. All the material for this blog, to include an updated version of this post, is now available on my new WordPress blog site at www.oldtopographer.net.

You can access the new version of this post at http://oldtopographer.net/2011/01/23/inter-american-geodetic-survey/

Thanks!

- Brian

_____________________________________________________________________________

The Inter-American Geodetic Survey (IAGS) was one of those extremely successful, yet little known, US Army (and later, Dept. of Defense) programs established after WWII.

The IAGS was created specifically to assist Latin American countries in surveying and mapping their vast internal regions that were either poorly mapped or entirely unmapped. The IAGS was established in 1946 as part of the Army Map Service and was headquartered at Fort Clayton in the Panama Canal Zone. The Army Map Service set up a complete survey, cartographic and map reproduction school at Fort Clayton and over the next 30 years trained thousands of military and civilian personnel from most Latin American and Caribbean countries. Attendance at the IAGS school at Fort Clayton was seen as right of passage for many up and coming officers in Latin American militaries, and it was common to run across senior officers - colonels and generals - from South American countries who talked fondly of their time spent at Fort Clayton, taking surveying or cartographic classes (one infamous graduate of the IAGS schools just happens to be Panamanian dictator Manuel Noriega, who attended the cartographic school in the 1960s).

The IAGS didn't just provide training.  It also provided the equipment and personnel to assist the participating countries in establishing their own self-sufficient mapping and surveying programs.  The goal was to provide the training, equipment and technical support but have the individual countries take over their own mapping efforts.

Now, I'm not going to pretend that the IAGS was all altruistic good-will on America's part.  We learned the hard way during WWII that many Latin American countries were at best reluctant allies, at worst active sympathizers with the Nazi regime.  At the end of WWII the political systems in these countries ranged from shaky democracies to hard line dictatorships.  The US Government became concerned about the effects of political unrest and Communist influence in the region, and instituted a number of programs designed to bring Latin America firmly under American influence and to foster democratic principles and improve economic conditions.  The IAGS was just one of many programs created as part of this effort.  One extremely important benefit the IAGS provided back to the US was that we were able to get American personnel on the ground in these countries to make detailed evaluations of local conditions (after all, that's what surveyors and cartographers do, right?) and we got maps that were created to US standards for vast areas of Central and South America.

According to all the accounts I've read and my own direct experience with the IAGS in Central and South America, the program was a great success. The goals of the IAGS were warmly embraced by most countries, who realized they utterly lacked the resources and training needed to map their own territories. IAGS liasion personnel were permanently assigned to each country, working out of the US embassies, and developed deep and lasting ties with government, military and business leaders.  IAGS personnel were very highly regarded in most countries, and I've heard more than one old-timer talk about how whenever they flew into a country to work and the local customs agents saw the distinctive IAGS logo on their luggage they were swiftly and courteously passed through customs without inspection or interrogation.

My introduction to the IAGS came when I attended the Defense Mapping School's Mapping, Charting & Geodesy Officer's Course at Fort Belvior, Virginia back in 1982.  By then the IAGS had been, or was in the process of transforming into, the Defense Mapping Agency International Division (I'm running on memory here, so please forgive any errors). However, the IAGS logo was visible throughout the building, and we received a short orientation brief on IAGS operations.  My next contact came in 1990 while working in Honduras as part of an airfield construction task force.  My team's job was to conduct route reconnaissance and terrain evaluation of large sections of southern Honduras.  We made contact with the Honduran IAGS liaison officer, Emory Phlegar.  Emory was a long time IAGS hand who had 'gone native' - he married into Honduran society and seemed to know everyone and everything that was going on in that small, poor country.  He provided us a wealth of information and with a simple phone call opened a number of doors for us with the Honduran Instituto Goegrafico Nacional (National Geographic Institute).

Three years later I was stationed at Fort Clayton, Panama, and headed up the geographic analysis team supporting US Army South and US Southern Command.  This job put me in close and frequent contact with the last remnant of the IAGS in the old Canal Zone. Southern Command and the Defense Mapping Agency (DMA) ran a joint map warehouse on Albrook Air Force Station.  The Air Force took care of ordering, stocking and issuing standard US maps to all US military operating in Central and South America.  In the same building the Defense Mapping Agency ran a small but very interesting and critical 'local products' warehouse that received and stocked maps printed by the different countries who had been part of the IAGS.  By agreement, DMA received 100 copies of every map printed by the participating countries. Quite often these maps were the only representation of Central and South American land areas available to the US military, and we relied heavily on this map supply. In fact my unit acquired an early large format Xerox copier specifically to make copies of these maps for Army use so as not to draw down the limited stock kept by DMA.

Additionally, DMA continued to operate a topographic and survey instrument repair shop out of the building.  This was a one man show, employing an instrument repairman who fixed or calibrated any equipment that had been loaned to countries participating in the IAGS.  Much of the loaned equipment was simply too big to pack up and send back to Albrook to be worked on, so this lone repairman spent a lot of time on the road traveling from country to country repairing equipment.  Most of what he worked on was obsolete by US standards, but was still perfectly serviceable and suitable to the Latin American countries that couldn't afford anything more modern. As such, his workshop at Albrook was a fascinating mix of spare parts bins and machine tools.  Since he dealt with a lot of obsolete equipment I'm sure he had the skills and equipment needed to fabricate any broken or worn part.

Unfortunately there is very little information about the IAGS on the web.  Not even Wikipedia has a dedicated page, and only catalogs indirect references to the agency. This is a shame, because the IAGS was a landmark cooperative effort that yielded enormous benefit for all countries involved, and its story needs to be out there for everyone to read. Somebody at the National Geospatial-Intelligence Agency (the successor to the Defense Mapping Agency) or the Corps of Engineers needs to write up a short history of the IAGS and its accomplishments while the participants are still around to tell their stories.

But for now it is You Tube to the rescue!  I found this film, part of the Army's 'Big Picture' series, covering IAGS operations:



Enjoy!

Brian

Happy Birthday Dad!

 Guess who's having a birthday!

The original leatherhead!

Eighty two years old and still going strong!

There are very, very few people in this world I look up to and admire, and my Dad is at the top of that short list.

Happy Birthday Dad!  We all love you and wish we could be with you to celebrate.

Brian, Roberta, Liz and Aileen

Grab A Real Strong Cup of Coffee And Watch This

One of the hundreds and hundreds of instructional films created by the Army that did more to cure insomnia among the troops than anything else, but still fun to watch.  It sticks with our theme of compasses and land navigation.  I like a lot of the old-timey touches in the film - M-14 rifles, bright yellow name tapes and enlisted uniform stripes, burlap covers on the helmets (nobody ever did that in the real Army), poncho rolls on the pistol belts, fatigue shirts without cuffs on the sleeves (apparently one of McNamara's cost saving initiatives - geeze) and the classic and ever popular M-1951 field jacket.

So here you are, from 1966 and straight from Stump Neck, Maryland, US Army Training Film 3721, Basic Map Reading:



(Don't worry, I'll flash the room lights twice when the film is over so you know when to wake up.)

A Man for All Seasons

December 31st is the birthday of one of the greatest Americans of the 20th Century.

George C. Marshall was born in 1880 in Uniontown, Pennsylvania.  He attended the Virginia Military Institute, graduating in 1901 and then competing for and winning one of the few coveted officer commissions reserved for non-West Point graduates.  In virtually every assignment Marshall stood apart from his fellow officers, exhibiting a keen military mind and outstanding leadership traits even as a junior officer.  One of his peers, observing the young Lieutenant Marshall direct what was essentially a regimental-level exercise in the Philippines commented to his wife "Today I watched the future Chief of Staff of the Army at work".

Few people understand that the US Army didn't just magically appear on the battlefields of WWII and decisively defeat the Germans and the Japanese.  The foundations of the American Army that won WWII were set years before Pearl Harbor by George C. Marshall.  It started in the trenches of WWI, where a dynamic young Marshall was assigned as the G-3 (Operations) of the 1st Division and later the Assistant G-3 of the American Expeditionary Force (AEF).  Marshall saw first hand the devastation and human suffering caused by a stalemated war that had devolved into static trench warfare, and the effect that poor leadership and poor military decision making had on units and individuals.  He learned those lessons well and carried them with him as he moved up in rank and responsibility.

Between 1918 and 1939 Marshall had a number of assignments that, in retrospect, were key to his success as Army Chief of Staff.  The first was his assignment as Aide-de-Camp to General John J. Pershing.  One of Marshall's roles in this assignment was in helping General Pershing compile the Army's official history of its involvement in WWI.  Marshall was able to spend time studying the broader issues that impacted America's involvement in the war, particularly in the areas of training, leadership, military force structure and industrial readiness.  By this time Marshall was already thinking at the strategic level and he understood that the core issues of WWI had not been settled with the armistice.  He concluded that America would probably be at war again on the European continent within the next 30 years.

Marshall's next key role came in 1930 when he was assigned as the Assistant Commandant of the Infantry School at Fort Benning, Georgia.  Marshall turned the Infantry School into a laboratory, investigating and testing new tactics and force structures.  Marshall understood that mobility and firepower were the keys to success on future battlefields, and he put sharp young officers like Omar Bradley, Joseph Stillwell, Walter Bedell Smith and Matthew Ridgway to work revamping Army doctrine to reflect this new thinking.  Out of this work came the concept of the smaller, more agile triangular division with more organic firepower, motorization (the horse was about to be left behind), improved communications using the newfangled radio and the integration of armor and air support into a 'combined arms' concept.  What is fascinating is that advanced military thinkers in Germany were working along the exact same lines, developing the concept of 'Blitzkrieg' - the lightning war spearheaded by fast moving armor forces.

After the Infantry School Marshall was assigned as Commander of the 8th Infantry Regiment in Georgia.  During this assignment he was also appointed as the district military commander for the Civilian Conservation Corps (CCC).  Most military professionals resented being 'stuck' with the CCC responsibility by President Roosevelt, but Marshall understood that the CCC would provide vital experience to Army junior officers and NCOs.  In future wars involving mass mobilization officers and NCOs would need experience in routine tasks like receiving, housing, training, feeding, moving, caring for, accounting for and employing large groups of young men.  The CCC role provided just this experience, and Marshall embraced it.

Marshall's next assignment (1933 - 1936) seemed to him, and his peers, as banishment to the wilderness.  A petty and vindictive Army Chief of Staff, General Douglas MacArthur, had Marshall assigned as the senior advisor to the the Illinois National Guard.  Apparently MacArthur was upset at Marshall's support of the CCC program (something MacArthur hated and fought endlessly with Roosevelt about).  The politically connected Illinois National Guard wanted a talented Regular Army officer to be assigned as advisor, but National Guard advisor positions were viewed by the Regular Army as something second-tier officers got stuck with.  MacArthur saw this as an opportunity to placate the Illinois politicos and send Marshall a message.  In typical Marshall fashion he made full use of the assignment, evaluating the National Guard from the inside, developing a keen understanding of their training and readiness and mapping out the political sub-structure that supported the National Guard systems in most states.  This understanding would be critical when Congress federalized all National Guard units for integration into the Regular Army after Pearl Harbor.

After the National Guard advisor position Marshall was promoted to Brigadier General and went on to command the 5th Infantry Brigade in Washington State and more CCC involvement.  By 1938 the threat of war in Europe was again looming and Marshall's talents were finally recognized at the national level.  He was pulled to Washington D.C. to head the War Plans Division.  In 1939, on the recommendation of the outgoing Army Chief of Staff General Malin Craig, Marshall was promoted to four star rank and appointed Army Chief of Staff by President Roosevelt.  I consider it one of Roosevelt's most prescient moves that he recognized Marshall's talents and promoted him over dozens of other Army general officers with more seniority.

Finally, George C. Marshall's experience and skills were turned to what he had been anticipating, yet dreading, since 1918 - preparation of the US Army for global conflict.  With the foundations in place and solid support of the President, and Secretary of War Henry Stimson, Marshall set in motion his plan to prepare the Army for modern war.

The new Chief of Staff understood better than anyone that the next war was going to be fought by young Americans who were not just citizen soldiers, but they were the sons and husbands of American citizens and as such deserved to be led by the very best.  Yes men would die, but they should not die needlessly or because of a failure of leadership or training.  It was the Army's responsibility to provide the very best officer and NCO leadership and training possible.  Towards that end, Marshall cut a wide swath through the Army, firing or retiring hundreds of senior officers who were too old, too out of shape or just plain incompetent.  (One politically dangerous move was his firing of virtually all National Guard division commanders soon after their divisions were federalized.  He realized from his National Guard advisory experience that these commanders were little more than political hacks and were not up to commanding divisions on the modern battlefield.)  At the same time Marshall reached down into the Regular Army officer ranks and pulled up dynamic young men he knew could perform.  Virtually overnight talented officers like Omar Bradley, Mathew Ridgway, Mark Clark, Walter Bedell Smith and Dwight Eisenhower found themselves jumping rank and position on the fast track to senior command or staff positions.  As an example, in early 1941 Omar Bradley was promoted directly from Lieutenant Colonel to Brigadier General, bypassing the rank of Colonel.  A year later he wore two stars and was commanding the 82nd Infantry Division (before it was designated an airborne division).  If General Marshall knew you and you measured up to his exacting standards you could expect fast promotions and increased responsibility.

General Marshall also revolutionized the Army machinery that created small unit leaders.  Prior to 1940 you could still become an Army officer by direct political appointment or even election or acclimation by members of the unit (this is how Harry Truman got his commission in WWI).  While this system only existed in the National Guard system at the time, it was still viewed as a viable method of obtaining a commission.  Marshall put an end to all that and standardized policies and procedures for obtaining officer rank in the Army.  He also knew the Army's demand for unit leaders at the platoon and company level would be almost insatiable and the existing commissioning programs, West Point and ROTC, would not meet the demand.  Marshall also knew that the Army already contained a vast pool of potential officers - the enlisted ranks.  Every day thousands of young men were volunteering or were being drafted who had some college experience and would make excellent officers.  Marshall directed the establishment of the Officer Candidate School (OCS) program at Fort Benning.  Following a curriculum developed by General Omar Bradley the OCS program took talented and educated enlisted men and turned them into Second Lieutenants.  This program was so successful that it became the primary commissioning source for the US Army in WWII - far surpassing the numbers of officers generated out of West Point and the college-based ROTC programs.

Even as Army Chief of Staff, General Marshall never lost focus on or sight of the individual soldier.  Immediately after Pearl Harbor his advisors notified him that no more silk would be imported due to the war with Japan (the world's major producer of silk).  Silk was now classified as a strategic material and it was up to Marshall to determine how the Army's share of it would be used.  There was a lot of demand for silk - for use in uniform neckties, socks, flags, pennants, even as powder bags for artillery ammunition - and it was clear the available supply would not last long.  Marshall directed that the available silk be reserved for just two uses - as parachutes and as award ribbons.  The General understood that award ribbons were important to the soldier.  They were (and still are) the Army's visible recognition of service and valor, and those little bars of silk would end up meaning a lot to the millions of soldiers just entering military service.  Award ribbons made of dyed cotton or wool look like junk compared to silk, and Marshall knew that.  The soldier deserved the best, and only silk would do for this important purpose.  With the development of nylon for use as parachute canopy material early in the war virtually the entire Army stock of silk ended up being used for the production of award ribbons.  General Marshall knew it would be important to the common soldier, so it was important to him.

George C. Marshall, like Cincinnatus, wanted nothing more than to retire and live out the rest of his life as a gentleman farmer and historian.  On November 18th 1945 he retired as Chief of Staff of the Army and he and his wife fled to their small estate in Virginia.  The most powerful military figure in the world finally found peace and pleasure in puttering around his house, painting shutters and planting shrubbery.  Less than ten days later he received a personal phone call from President Harry Truman asking him to become his ambassador at large and travel to China to try to untangle that growing mess.  Marshall's sense of duty would not allow him to say no, and he was launched on his second career as diplomat, Secretary of State and father of the Marshall Plan which financed the reconstruction of Europe and ensured that Western Europe remained free of Soviet domination.

George C. Marshall died on October 16th, 1959 at Walter Reed Hospital in Washington, D.C.  I have been told that at the announcement of his death grown men, many of them with stars on their shoulders, broke down and cried.

In my estimation George C. Marshall is the key figure in the story of America's success in WWII.  General Marshall is the reason we fielded the excellently trained, equipped and led armies we did between 1942 and 1945.  More than any one person he was the architect of America's victory in WWII and shaped the free world that came after.

He was the indispensable man.  The man for all seasons.

Brian

Farewell Kodachrome

The last roll of Kodachrome color slide film was processed yesterday.  Kodak abandoned (yes, abandoned) the iconic film format in 2009, and the last Kodachrome film processor, Dwayne's Photo in Parsons, Kansas processed the last roll yesterday.

I am sure there are thousands, perhaps hundreds of thousands, of exposed yet undeveloped rolls of Kodachrome film laying in camera bags, desk drawers, automobile glove boxes, purses and  odds 'n end boxes around the world.  They are images lost.  Almost.  Apparently Film Rescue International in North Dakota will process exposed Kodachrome film into black and white prints.  Better than nothing, I guess.

Farewell old friend.

Which Way North? (Part II) - The Pocket Transit

In Which Way North? (Part I) we discussed the history of the magnetic compass and talked a bit about magnetic declination.  Now let's start looking at some specific compass designs and discuss why they were important.

To start we'll look at a compass design that is uniquely American and was born of the late 19th Century explosion of mining and mineral exploration in the US.  This compass was originally conceived to fit a very specific need, but it was so well designed and executed that it found use in a wide variety of applications and industries.  It continues to be produced today, over 100 years since its introduction and little changed from its original design.

The Brunton Pocket Transit was patented in 1894 by David Brunton, a Colorado mining engineer.  Brunton was frustrated by the number of survey instruments a mining engineer and geologist had to carry around with him (and I say 'him' because mining engineering and field geology was an exclusively male profession well into the 20th Century).  In the late 1800s it was not unusual for engineers and geologists doing basic exploratory mineral mapping to lug around full sized survey transits, surveying compasses, tripods, clinometers, and plane tables. These instruments offered a high level of accuracy that simply wasn't needed for exploratory surveys.  As an engineer himself Brunton realized that what was needed a portable device that allowed field survey personnel to do fast and accurate exploratory quality surveys without being burdened down by equipment that was heavy, expensive and difficult to set up and use.  These men were in the business of discovering, verifying and mapping mineral deposits that covered vast areas.  Huge sums of money were at stake as mining and mineral companies scrambled to secure valuable leases on the stuff that was fueling America's exploding industrial economy - timber, gold, silver, coal, iron ore, chromium, nickel, bauxite, petroleum and dozens of other minerals that were key to America's growth.  Field engineers and geologists needed to move fast, do rough mapping and get that information back to the office for the development of lease maps and boundary descriptions.  They didn't need to be burdened with heavy, sensitive and fragile survey gear if that level of accuracy wasn't required.  David Brunton recognized the problem and set to work developing a solution.

What Brunton came up with as a pocket-sized device that incorporated an accurate magnetic compass with a sighting vane, a clinometer, a level and a large mirror with a sight line.  Housed in a machined aluminum case (still an expensive material in the late 1800s), it was rugged, reliable and useful.

Brunton named his instrument the 'Pocket Transit', a lofty title for a fairly rudimentary mapping device.  But the name served its intended purpose; in the mind of the engineer and geologist it set the device apart from the common handheld compass.  Here was a professional instrument that offered a level of accuracy and functionality not found elsewhere.

Brunton's 1894 model Pocket Transit

Brunton had more than marketing on his side.  The Pocket Transit actually delivered where it mattered - in the field and in the hands of engineers and geologists across North America.  It delivered all the functionality and accuracy needed to get the job done.  It ended up being the perfect device for the job at hand.

Demand for Brunton's device increased steadily and improvements were introduced.  An additional bubble level and a cover mounted peep sight were added in 1912.  In the same year Brunton introduced modifications to the case that allowed mounting the instrument on a non-magnetic tripod or jacobs staff.  (It's interesting that in his 1894 patent application Brunton derided other compass designs that needed to be tripod mounted, but in the 1912 patent application he discusses tripod mounting like it's the greatest idea since sliced bread.)  Somewhere between 1894 and 1912 the Pocket Transit acquired the ability to pre-set magnetic declination by use of an adjustment screw on the side of the case.  By 1926 Brunton's design had fully matured with the addition of a bullseye level for improved leveling and the addition a percent grade scale to the clinometer.  From this point forward it was minor improvements in materials, manufacturing techniques and the added availability of different compass ring layouts (degrees, quadrants, mils, etc.)

A 1926 patent model of the Brunton  Pocket Transit.
Note the round level and the percent grade indices
at the bottom of the clinometer scale.  This is the basic
design still in production today.

One of the reasons Brunton's pocket transit was
so damned useful is that he made it a complete package.
Early in the production of the pocket transit Brunton started
engraving sine and tangent tables on the lid.  Using these
tables in conjunction with the clinometer an engineer could
quickly and accurately determine heights of objects like trees
or cliff faces.  To this day Brunton includes the sine and
tangent tables on the lids of all pocket transits.
So damned useful!

From the beginning David Brunton licensed the Colorado instrument maker William Ainsworth & Sons to produce the pocket transit.  After Brunton's death in 1927 Ainsworth purchased the manufacturing rights to Brunton's designs and continued manufacturing and improving the Pocket Transit through the late 1960s.  In 1972 the production rights and the Brunton name were purchased by the Brunton Company of Riverton, Wyoming.  The Brunton Company continues to manufacture this basic design.

The Brunton design was so well thought out that engineers and geologists quickly developed field techniques keyed to the Pocket Transit's unique layout and construction.  The best example is the determination of the strike and dip of rock formations.  Most sedimentary and metamorphic rock formations are not horizontal.  They were all deposited in horizontal layers but over geological time (i.e., millions of years) those horizontal layers have been warped and deformed by pressure and other geological forces.  One of the keys to understanding these forces is mapping the strike (the horizontal angle of deformity) and dip (the vertical angle of deformity) of individual rock layers.  Before the Brunton Pocket Transit the measurement of strike and dip was a clumsy process involving two separate devices - a field compass (often a fairly large and somewhat fragile device) and a clinometer.  With the Brunton the process is quick and simple - open the instrument and lay it horizontally against the rock formation.  Keeping the edge of the instrument in contact with the rock face rotate it up and down slightly until the circular level is centered.  Note the magnetic azimuth as indicated by the compass needle.  That is your strike.  Score a line on the rock face horizontal to the pocket transit using a piece of chalk or small piece of rock and remove the pocket transit.  Make another score mark that is perpendicular to the horizontal mark you just made (your mark should look like a 'T').  Place the Pocket Transit along this perpendicular mark and measure the angle of slope using the built in clinometer.  This is your dip.  It takes longer to describe than it does to do it in the field.  This is the standard measurement technique for strike and dip, and every college and university geology department in North America teaches it as part of their field geology curriculum.

From the University of Calgary website.  Measuring the strike
of a rock formation using a Brunton Pocket Transit.

From the University of Calgary website.  Measuring the dip of
a rock formation using the Brunton Pocket Transit.

My introduction to the Brunton Pocket Transit came in the mid-1970s while studying geology in college.  We learned strike and dip measurement techniques early on in the field methods class, and later during our summer field geology course we ranged across the southwestern United States, making thousands of strike and dip measurements in an effort to understand the geologic processes that formed the unique landscape of that region.  I saw the Pocket Transit as a useful but fairly limited device, suited only to the field geologist.  Years later while attending a course at the Defense Mapping School at Fort Belvior, Virginia, our class got an intensive block of instruction on the use of the Pocket Transit not just for strike and dip measurement but for height determination, precise azimuth determination, basic plane table survey work and rough site layout.  I finally saw the full potential of the Pocket Transit and purchased my first one soon after.  That Pocket Transit has seen service in Kuwait, Honduras, Panama, Germany, Bosnia, Korea and across the US.  It has been a constant companion on hundreds of field surveys, assisting with tasks like mapping out refugee camps on the Empire Range area of the Panama Canal Zone, measuring road grades along the Pan-American Highway in Honduras and fixing North Korean observation point locations along the Korean DMZ.

The Brunton Pocket Transit doesn't measure horizontal angles as well as a conventional transit, it doesn't measure vertical angles angles as well as a theodolite, sextant or even an Abney hand level.  If you need to shoot azimuths using handheld techniques the Army lensatic compass is a better tool.  However, the Pocket Transit does all of these tasks well enough, and puts everything needed into a compact, easy to carry package that really does fit into your pocket.  (In his patent application David Brunton noted that the instrument fits nicely into a vest pocket - therefore the name pocket transit).

Let's have a look at some Brunton Pocket Transit variations (click on the pictures for an enlarged view):

This is a modern incarnation of the Pocket Transit - a glass filled composite
body version.  This particular Pocket Transit is almost 20 years old
and has been used around the world, and it still looks new.

This is a particularly nice WWII era Pocket Transit manufactured in 1943.
This model is graduated in mils (6400 mils in a circle).  Designated the
M-2 Compass, it was designed for use by artillery troops who need a more
discreet subdivision of the circle for accurate artillery gun laying and spotting.
A variation of this model is still used by the US Army and USMC today.

An early induction dampened model graduated in degrees

A nice post-war model graduated in quadrants instead of degrees.
Most early Pocket Transits were sold with the quadrant setup rather than
degrees.  The use of quadrants was the accepted method of noting direction
within the engineering and geology community up through the 1970s.  Brunton
still sells a modern version of this layout, but it really is useless for general
navigation purposes.  If you want to do land navigation with a Pocket
Transit get the model laid out in degrees!

As you can tell, I think the Brunton Pocket Transit is a nifty little tool.  But it is not a novelty, not something to be put on a shelf to be admired.  The Pocket Transit is designed and built to be used.  It represents American ingenuity at its best.  From 1894 on the Pocket Transit ended up being used in all corners of the United States, doing useful, often rough duty helping to map American and her natural resources.  Rugged, reliable, useful.  American to the core!

Brian

In writing this blog post I relied heavily on several sources that I feel need to be acknowledged.

First is William Hudson's excellent website About Brunton Pocket Transits.  Mr. Hudson's site is the most complete compilation of information about Pocket Transits on the web, and should be the starting point for anyone interested in finding out more about these great little devices.  Thanks you Mr. Hudson.

Next is Dr. Peter H. von Bitter's article The Brunton Pocket Transit, A One Hundred Year Old North American Invention.  Originally written in 1995 for the journal of the History of the Earth Sciences Society to celebrate the 100 year anniversary of the invention of the Brunton Pocket Transit, von Bitter's article forms an excellent short history of the man David Brunton and his famous invention.  Thank you Dr. von Bitter.

Although not source, there is an scanned copy of a 1913 Ainsworth bulletin available on the the Surveying Antiques website.  This bulletin describes the various ways to hold and use the Pocket Transit and is an interesting overview of the instrument and its uses.