Old School Map Making

I was wandering through YouTube at work today (shhhhh…) and stumbled on this neat old Army training film that describes the steps required to make a paper topographic map, circa 1973. The steps in this movie really didn’t change for about 60 years, from the late 1920s to around 1990 or so.  In fact, not a whole lot if the equipment changed, either. Sure, there were a few improvements here and there – better materials, more accurate surveying equipment and better aerial photography cameras – but the basic steps remained pretty much unchanged.  Of course today it is all different; digital satellite imagery, GPS, LiDAR and desktop computers have fundamentally changed the mapping profession. But for now let’s celebrate the old ways, when men were men, theodolites didn’t have any electronic components and cartographers wore ties while they worked at their light tables.  This movie (broken into three parts by YouTube) was filmed mostly at the old Defense Mapping School at Fort Belvior, VA: Part I:

Part II.  Now, part II is interesting because I swear the soldier who is shown working at 5:40 is an old friend, Norm Price.  I first met Norm at Fort Lewis in in 1987.  Norm had been a Cartographic Technician warrant officer who recently converted to the new Terrain Analysis Technican field (MOS 215D) just before I met him.  If I remember correctly he entered the Army in the late 60’s, so it is entirely possible for young Specialist Price to have appeared in this film:

And Part III:


– Brian

Spy Satellites Declassified

A KH-9 Hexagon Imagery Satellite.  The thing’s as big
as a Greyhound bus!

On 17 September 2011 the US declassified the KH series of satellites and their mission information.

Guess now I can tell my wife what I was doing for most of those 23 years I was in the Army.

What’s not discussed in the story, and I won’t go into too much detail until I know for sure it’s OK to discuss it in full, is the contribution these satellites made to the DoD’s world-wide mapping program.  Suffice to say, without these birds we would not have been able to accurately map the vast territories of the Soviet Union, Eastern Europe, China and all the other hostile places we thought we might have to go fight in.

More to follow…  Maybe.


The Military Lensatic Compass

I’m going to kick off our formal evaluation of compass accuracy with the a design that has been in continuous use  for over 60 years and has seen use by millions of individuals.  It is perhaps the most tested compass design in history, with documented use in jungle, desert, woodland and arctic environments around the world.  It is tried and true and is one of my favorite compass designs.

It is the US Army’s Model 1950 lensatic compass.

The M1950 compass is a design born of war.  It’s predecessor, the M1938 lensatic compass, was developed and adopted just as WWII opened.  It was a good design that was easy to manufacture.  Equally important, the adoption of the M1938 compass allowed the Army to standardize land navigation training, simplify it and teach it to the millions of young men who were being drafted into the Army and Marines. The experiences of war taught the Army a few things about compass design.  First, it proved that the lensatic compass design was a good one.  It was accurate, reliable and versatile.  With its compass card graduated in both degrees and mils it was usable by the both infantry and artillery.  The military liked the basic design and stuck with it.

A Model 1938 (M1938) lensatic compass manufactured
by the Superior Magneto Company of New York
Superior Magneto appears to have been the prime supplier of this
compass design during WWII

However, wartime experience also highlighted some shortcomings in the M1938 design.  It was somewhat fragile.  While not a toy, the M1938 was lightly built – just two stamped aluminum cups fitted together to form the compass bowl and lid.  It had no mechanism to lift the compass card off of the the pivot needle when the compass was closed.  A lot of compasses were damaged when the the tip of the pivot needle gouged or cracked the pivot jewel through rough handling.  But perhaps the biggest shortcoming of the M1938 compass is that it had no dampening mechanism. This meant that the compass card would swing wildly and would take a good number of seconds to settle down to the point where the Soldier could get an accurate reading.  There were some versions of the M1938, those manufactured by the W. E. Gurley Company (a leading manufacturer of surveying instruments), that included a needle lift mechanism that with practice could be used to brake or slow the compass card oscillations.  However, the vast majority of compasses were manufactured by the Superior Magneto Corporation and did not include this needle lift mechanism.

After WWII the Army incorporated induction dampening into the M1938 design.  Induction dampening is a beautifully simple concept.  It takes advantage of the inductive magnetic field generated between a swinging compass needle and a highly conductive but non-magnetic alloy like copper.  When a magnetic needle (or bar) is placed inside a cup made of copper and the needle swings (oscillates) that movement causes a slight magnetic eddy current to form.  When the needle swings to the left the eddy current pulls it to the right.  When it swings to the right the eddy current pulls it to the left.  The eddy current is self-canceling; as the needle oscillations decrease the eddy current strength decreases and very quickly the needle settles down and is aligned with magnetic north.  Simple, elegant and effective.

A late model M1938 compass with induction dampening.  This is
a transitional design, bridging the gap between the original M1938 compass
and the the M1950.  The white colored compass bowl is actually
a copper cup that forms part of the induction dampening system.
This compass was made in December 1950 by the
Marine Compass Company out of Pembroke, Massachusetts.

However, by the late 1940s the Army decided it was time for a whole new design.  The Army took the best functional elements of the M1938 compass – the lensatic sighting design and the combined degree and mil scales on the compass card – added induction dampening, a needle lift device, a much larger sighting lens and a larger thumb loop and placed it all in a beefed-up waterproof aluminum housing.  The resulting compass was designated the M1950 Lensatic Compass.  It is a rugged, versatile device that has remained in use with the US military for over 60 years, pretty much as originally designed.

M1950 Lensatic Compass
This particular compass was manufactured in February1953 by the
Marine Compass Company out of Pembroke, Massachusetts.   The
cloudy dial cover is the result of the plastic aging.  Remember, this compass
is almost 60 years old!
Same compass with the cover closed, showing the manufacturer and
manufacturing date.

Fast forward almost 60 years and the same compass design is still in use by the US military, and it doesn’t look like they have plans to switch designs any time soon.

M1950 Lensatic Compass manufactured in 2010 by the Cammenga Corporation
out of Michigan.  This is a military issue compass that uses tritium inserts
for night time illumination.
The same compass with the cover closed.  At the time of this writing
Cammenga has been the sole supplier of lensatic compasses to
the US military for over 10 years.

Since 1950 this compass has been produced by a number of manufacturers, including the Marine Compass Company, Jay-Bee, Union Instrument, Cammenga and even Lionel (yes, the train people!).  However, it seems that the single biggest manufacturer of M1950 compasses was Stocker & Yale out of Massachusetts.  I don’t have any specific production numbers for these compass manufacturers so my claim is based solely on personal observation.  Based on the compasses I was issued in the Army and what I see for sale on auction sites or in surplus stores it appears that Stocker & Yale had the highest production numbers.

Now, the US military doesn’t just turn to a manufacturer and say “Make it!”  Like all things military there are clearly defined specifications.  It doesn’t matter if you are building an aircraft carrier or a handheld compass, there must be clearly spelled out specifications!  So it is with the M1950 Lensatic Compass.  Today’s compasses are built and tested in accordance with the DOD military performance specification known as MIL-PRF-10436N (Performance Specification, Compass, Magnetic, Unmounted, Lensatic, Luminous, 5 Degree and 20 Mil Graduations, With Carrying Case).

The document that spells out the design, construction,
performance and testing requirements for the
lensatic compass

(I should note here that the current specification does not use the ‘M1950’ designation.  I’m not sure when the US military dropped the designation, but for our purposes we’ll continue to call it the M1950.  It’s the same compass.)

The discussion of this performance document is important because the M1950 compass is the only US produced handheld compass I am aware of that is built to a specific performance specification, and is regularly evaluated against this performance specification by an outside agency.  If any test batch of compasses fails the evaluation the devices never make it out of the factory.  The M1950 is a purpose-built device designed to meet a clearly laid out specification not just for accuracy but for shock resistance, water resistance, illumination, thermal shock, durability and service life.  Manufacturers of other compasses may have their own internal standards (and many are quite good), but the M1950 is the only handheld compass you can buy that is designed to meet demanding military standards and is rigorously tested by an independent agency to ensure it meets those standards.

So just how good is the M1950 compass in the real world?  Pretty damned good!  The 58-year old example I show above that was made by the Marine Compass Co. is still perfectly serviceable and would probably meet all of today’s performance specifications for accuracy and durability.  I have other examples in my collection that have clearly seen hard use, some with broken components or cracked dials, but they still provide reliable and accurate readings. The M1950 compass is a device that is hard to kill.

I believe that the key to the M1950’s ruggedness is the fact that is it not a liquid dampened design.  Liquid dampening (where the compass needle or card is suspended in fluid to reduce oscillation) is very effective but is a more fragile design than the induction dampening used in the M1950.  With the liquid filled design the compass needle or card must be sealed inside a leak proof capsule*.  The problem is, compass manufacturers have not yet figured out how to make a leak proof capsule.  I have over 15 liquid filled compasses in my personal collection.  About half have air bubbles inside the capsule, a sure indicator that the fluid is leaking.

How accurate is the M1950 compass?  Every M1950 I’ve used (and after a 23 year Army career I’ve used a lot of them) has at least met, and many exceeded, the performance specification for accuracy.  Now this is where I need to come clean on my evaluation of the M1950.  It is not the most precise handheld compass available.  This compass’ biggest design limitation is that the compass card is divided into only 5 degree increments; pretty coarse even for handheld use.

Compass card of the M1950 compass.
Note the inner degree ring (in red) laid out in 5 degree increments.  The outer
ring (in black) is set out on mils (6400 mils to a circle).

This means that the average user, the common Soldier, can only discern and measure to half of that increment – 2.5 degrees.  Experienced users – mostly infantry and artillery Soldiers who use a compass regularly – can frequently get accurate readings to between 1.5 – 2.0 degrees. But to be realistic, 2.5 degrees is about as good as anyone can expect to get with this compass card layout.  The M1950 compass card design is a compromise.  The military needed to include a mils scale for use by the Field Artillery.  Mils offer more discreet division of the circle (a mil is 1/6400th of a circle), allowing for more precise azimuth determination – very important when you are calling in artillery strikes on distant targets.  To accommodate the mils scale it needed to be printed at the outer edge of the compass card, leaving less space to print the degrees scale.  This results in a coarse, less precise degree scale.

The military performance specification states that the compass must be accurate to within 40 mils.

“ Magnetic performance and compass error.  The compass shall be placed in a horizontal position on a fixed point and by means of the sighting mechanism, the compass shall be sighted on three targets of known magnetic azimuths approximately 120 degrees apart.  With no remedial action by the operator, before, at, or after, a reading shall be taken at each target.  The difference between the known azimuths and readings taken is the compass error.  An error greater than 40 mils or failure of the compass to function correctly shall constitute failure of this test.”

Since one degree = 17.8 mils, 40 mils is slightly less than 2.5 degrees.  Let’s round up and call it 2.5.

I have tested my 2010 production Cammenga compass at a known azimuth station and found it to be accurate to just over 2 degrees when used in the handheld mode and sighting on targets up to 150 feet away.  This compass very easily meets the performance specification.

Before I wrap up this blog post I need to add that the M1950 compass was merely one component of a land navigation system that the Army developed and adopted at the end of WWII.  Along with the M1950 compass came dramatic changes in how the Army mapped the world, developing standardized maps with overprinted grids (the Military Grid Reference System) and plotting tools.  It was all designed to simplify land navigation for the common Soldier, and is was so successful that the methodology is still in use today.

The US Army’s standardized land navigation ‘system’ included the M1950 compass,
standardized topographic maps, plotting tools and training materials.  It was an
extraordinarily successful program that is still used today.

Let’s wrap this up.  Here is my bottom line – I consider the the M1950 compass to be the best general purpose handheld compass available.  It is a proven design that is built and tested to exacting standards.  They are readily available new or used to civilians and are one of the best examples of trickle-down military technology I’ve seen.  If you spend any time in the outdoors you need a compass.  You might as well get the best available.  Get a M1950 Lensatic Compass.


– Brian

*One compass manufacturer, K&R out of Germany, claims to make a leak proof liquid capsule but I don’t think they have been on the market long enough to have proven the claim.

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

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 collars, 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

US Army FM 21-26

An Army field manual as a book of the month?  Just how interesting or relevant or important can a field manual be?

Well follow along, because for certain groups of people this FM is very interesting, relevant and important.

FM 21-26, Map Reading and Land Navigation is the Army’s map reading and land navigation handbook.  This manual has been in continuous publication and upgrade since 1941.  The current edition is dated 2005, with changes posted in 2006.  As part of a sweeping Army field manual re-designation the manual has been renamed FM 3-25.26*.  Regardless, it is still commonly referred to as FM 21-26, and that’s how we’ll refer to it here.

The Army seems to have adopted standard map reading and land navigation practices back in 1939, and published its first series of map reading and land navigation manuals in early 1941 (FM 21-25, Elementary Map and Aerial Photograph Reading and FM 21-26, Advanced Map and Aerial Photograph Reading).  Prior to 1939 map reading and land navigation was viewed almost as a black art, covered in non-standard texts targeted at officers and emphasizing field sketching and rudimentary survey as much as map reading and navigation.  A large part of the problem was that the Army had no map standards or centralized map production, so providing maps for unit operations was a local commander’s headache.  If you were a regimental commander and wanted a map of an area you put your regimental engineers to work either finding suitable maps from local or commercial sources, or you had them drawn up from field sketches or plane table surveys.

Army leaders realized that in the looming global war the old ways of producing and using maps would not do.  The Army needed dedicated map production assets that could produce millions of maps using common symbols, colors and scales.  This led to the creation of the Army Map Service and the standardization of map production on a global scale.  Once you had map standards in-place and maps in production you could develop standardized map reading and land navigation practices using these new maps.  FMs 21-25 and 26 were the result of that effort.  Finally, the Army had standardized map reading and land navigation texts it could use to train the millions of Soldiers about to be drafted into the Army to fight WWII.

After WWII, the establishment of NATO and the US Army’s realization that it would still maintain global warfighting responsibility the two field manuals were combined into one – FM 21-26, Map Reading, published in 1956.  The significant change in this manual was the introduction of the Military Grid Reference System (MGRS) based on the Universal Transverse Mercator (UTM) coordinate system.  The development of UTM and MGRS signified a revolution in mapping and mapping grids.  For the first time an army had an accurate low distortion world-wide grid system suitable for large scale mapping.  With MGRS and using just a paper map and a simple protractor a Soldier could uniquely identify his position anywhere on the face of the earth to within 10 meters.  MGRS is accurate, easy to teach, easy to use and virtually ‘soldier-proof’.

Updates to FM 21-26 came out every few years and the major changes seem to have been the simplification of basic principles and techniques, and the dropping of out-of-date or no longer needed procedures (like interpreting hatching to indicate landforms or the use of obsolete equipment).

Today’s FM 21-26 is map reading and land navigation distilled down to the basic, easy to learn and easy to execute functions.  It is not just map reading, but it is also the use of map substitutes (mainly aerial and satellite images), dead reckoning, field expedient direction finding, basic orienteering, terrain association and basic field sketching.  One key item of note is the Army’s method of teaching how to determine the magnetic to grid declination factors.  The lesser or greater angle method is hands down the easiest way to manage this often confusing issue.

Sure, FM 21-26 has a military focus.  It is, after all, an Army field manual.  The book spends a lot of time discussing the use of the MGRS system, how to orient, plan and navigate using MGRS.  It’s MGRS, MGRS, MGRS.  For years civilian students of map reading and land navigation had no use for this portion of the manual.  Topographic maps of the US either had no grids or had grids different than the MGRS grid, and US-based maps were printed at scales different than those used by the military.  This has all changed.  In just the past few years the US has (finally!) adopted what is known as the US National Grid.  The US National Grid is now being implemented for all USGS (US Geological Survey) large scale (1:24,000 and 1:100,000) topographic line maps, and the USGS is rushing the new US Topo series of maps into production.  So what is this new US National Grid?  It is nothing more than MGRS implemented for all USGS topgraphic maps of the US.  Remember, MGRS has always covered the world, but the US military does not produce maps of the US – that’s the job of the USGS.  The MGRS grid template always existed for the US, but the USGS never adopted it.  Until 2008, that is.  Driven by homeland security and disaster relief coordination concerns the USGS formally adopted MGRS, known as the US National Grid in the US, and is now producing maps to that standard.

Suddenly the discussion of MGRS in FM 21-26 becomes very relevant.  All the MGRS-based map reading techniques can now be directly applied (and are intended to be applied) to the new USGS topographic maps.  The only remaining issue is that of scale.  The US military produces large scale maps at 1:50,000 while the USGS produces large scale maps at 1:24,000.  While all the MGRS techniques apply to USGS maps, you can not use the standard map protractor (GTA 5-2-10) discussed in FM 21-26 since it does not have a 1:24,000 plotting scale included.  This isn’t a real problem because a number of manufacturers offer MGRS/US National Grid plotting scales for use with 1:24,000 scale maps.  One of my favorites is the Super GTA tool produced by Maptools.com.

Another great thing about FM 21-26 is that it is one of the few Army field manuals authorized for unlimited release.  This means the Army retains the copyright to the manual, but users are free to copy, reprint and distribute it without penalty.  As a result you can find free downloads of FM 21-26 all over the web and you can purchase inexpensive printed copies from retailers like Amazon.com.

So, if you like maps, are interested in map reading and land navigation, or have just a passing interest in these topics go get yourself a copy of FM 21-26!

– Brian

*The new designation of FM 3-25.26 seems a little unusual in the overall scheme of revised manual numbering.  I’d like to think that someone in TRADOC with a respect for military history recognized the significance of the original series of manuals, FM 21-25 and FM 21-26, and as a nod to tradition decided to redesignate the new manual as FM 3-25.26.

A Date That Will Live In Infamy

We didn’t ask for it, didn’t instigate it and didn’t want it.


But three years and eight months later we sure as hell finished it.



My salute to those that served on that fateful day in December, 1941, and to the millions that followed them into battle around the world to give us the liberty and prosperity we enjoy to this day.