I was going through some of my books and manuals this morning and stumbled across this old favorite. I spent a few minutes flipping through the pages and was reminded just what an absolute gem of a book it is. I consider it a minor classic.
As the author David Greenhood states in the first line of the Introduction, "This book has been written to be read rather than studied."
And so it should. This is not a textbook or a reference, it is an educated man's introduction to the concepts of topographic mapping. Authored by somebody who had a deep understanding of the subject and knew how to write for general audiences, it is readable, enjoyable and instructive.
Although this book was first published in 1944 and incrementally updated through 1964 it gives up little to the back half of the 20th century because it focuses on concepts rather than gizmos. There's not a word or hint of satellite navigation, space-based imagery platforms, world-wide datums and coordinate systems or computer-based mapping.
Greenhood's discussions on things like scale, perspective, contouring, projections and map compilation are some of the best and easiest to grasp that I've ever encountered. Greenhood's coverage of these concepts stand the test of time because they don't change over time. Scale is scale, perspective is perspective, whether you are looking at a paper map or a computer screen.
Some of the topics seem quaint, like how to properly sharpen a pencil or how to select the correct paper for drawing a map, but the discussions are charming and still somewhat useful in today's world. Most of the referenced publications are out of date and long out of print, but it's important to note that many of Greenhood's references were classics in their own right and are themselves worth hunting down and reading.
One of the real strengths of this book are the illustrations. Most of the illustrations are hand drawn and they remind us that a talented illustrator can easily convey complex information in ways photographs can't. The illustrations are expertly integrated with the text and provide support and reinforcement to the topics under discussion precisely when and where needed.
I bought my copy of Mapping in 1982 at the bookstore in the Smithsonian Museum of American History in Washington, DC. It has been paged through and referenced so many times the binding is starting to come loose. This morning I jumped out to Amazon to see if the book was still available. I'm pleased to see it is still published by the University of Chicago Press, but the price is an eye-bleeding $32.50 - quite a lot for a trade paperback. However, copies are available from used booksellers for very reasonable prices. I grabbed a new-condition copy from an Amazon partner bookseller for $6.95, not much more than the $5.50 I paid for my current copy back in 1982.
If you are at all interested in mapping, or want to introduce the concepts of mapping to a young audience this book is an excellent start. I've read a lot of books on mapping down through the decades and this is the best single volume introduction to the field I've ever read.
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:
My blog post last year about the Inter-American Geodetic Survey (IAGS) has has proven to be my most popular post, both in the number of pageviews and the number of comments. Although I'm not burning up the internet, it is interesting to track where visitor's interests lie. Surprisingly, my blog post is also the #2 return on Google searches against the term 'inter american geodetic survey' (it seems that the acronym IAGS is in use by several completely unrelated organizations that generate a lot of traffic, so searches against that term won't put my post anywhere near the top of the list).
I'm both elated and just a bit saddened by this outcome. Elated that I seem to have hit on poorly covered yet important subject that I can contribute significantly to, yet saddened that the Army Corps of Engineers continues to ignore the very crucial contributions their topographic services and personnel made to the professions of mapping, surveying and geodesy.
When I wrote the blog about the IAGS I noted that there's very little available information about the organization on the web and I tried to provide links to as much relevant info as I could find. One of the sources I completely ignored was the excellent article about the IAGS that appeared in the March 1956 edition of the National Geographic Magazine.
Before the National Geographic gave up serious scholarly writing for feel good stories about baby seals and the therapeutic effects of tree hugging it actually published some darned good stories about geography, exploration, and adventure. All three of these elements come together in this great story about the IAGS. It is probably the best, and perhaps the only, popular account of the agency's activities. So, follow this link and read about the Men Who Measure the Earth.
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.
Earlier this month the US Geological Survey (USGS) released their latest version of The National Map Viewer.
US National Map View of Maumee, Ohio
The same view of Maumee, Ohio with the aerial image
background turned on
The US National Map is not a map per se. You can't ring up the USGS and say "Send me a copy of the National Map." It doesn't exist as a single product. The US National Map is a collection of digital geographic and geospatial data that, when brought together, forms the foundational map of the United States. Here's how the USGS describes it:
"As one of the cornerstones of the U.S. Geological Survey's (USGS) National Geospatial Program,The National Mapis a collaborative effort among the USGS and other Federal, State, and local partners to improve and deliver topographic information for the Nation. It has many uses ranging from recreation to scientific analysis to emergency response.The National Mapis easily accessible for display on the Web, as products and services, and as downloadable data. The geographic information available fromThe National Mapincludes orthoimagery (aerial photographs), elevation, geographic names, hydrography, boundaries, transportation, structures, and land cover. Other types of geographic information can be added within the viewer or brought in withThe National Mapdata into a Geographic Information System to create specific types of maps or map views.The National Mapis a significant contribution to the National Spatial Data Infrastructure(NSDI) and currently is being transformed to better serve the geospatial community by providing high quality, integrated geospatial data and improved products and services including new generation digital topographic maps."
OK, like I said, it's a collection of digital geographic and geospatial data that forms the foundational map of the US. Geeze, I think government bureaucrats get paid by the word.
Here is the USGS's introduction to the National Map program and the National Map Viewer:
The National Map Viewer is the USGS's on-line portal to all the data that makes up the National Map.
The Viewer is pretty good (if you are at all interested, it is built on ESRI's ArcGIS Server technology) and offers some neat functionality. It will provide location information in a number of formats, including US National Grid coordinates, it has a pretty robust reverse geocoding feature (click on a building on the map and the map returns the street address for that location) and it will provide spot elevations from the national elevation dataset. You can do area and distance measurements, add text and simple graphics and even add data from external sources like a GoogleEarth KML file or a web mapping service. You can also bring up indexes for the USGS's standard map products like the US Topo series of maps and link to them for download as GeoPDF files. For advanced users the Viewer offers some pretty good search and query builder functionality, so you can find specific data that is embedded in the data layers.
There are some shortcomings, however. The print function is essentially useless and is perhaps THE major drawback of this Viewer. About all it does is grab a screen shot of your viewer and dumps it to a PDF file. The USGS needs to wake up and realize that people still want quality paper maps and with today's technology it should be easy to print a fully detailed paper map with things like a grid, scale indicator, geographic extents, legend, etc.
The Viewer also exhibits a common issue found in web-based maps - map content naming conventions can be pretty obtuse and downright confusing. While the Viewer does pretty good with the base data layer naming conventions, when you start using advanced features like the Query Builder you start to interact directly with the database field names. For example, if I'm building a query to identify all the wetlands in my county I'm presented with a list of 'Columns' (which are the database field names). Those column names are confusing and don't mean anything to most humans. We get to pick from selections named 'ATTRIBUTE' or 'OBJECTID' or 'SHAPE_Area'. There is an easy solution to this - the GIS professional building this map can establish what are called 'field alias' names - a human-friendly nickname for each of the information fields. ATTRIBUTE can be displayed as 'Wetland Attribute', OBJECTID can be displayed as 'Wetland ID' and SHAPE_Area can be displayed as 'Wetland Area'. This naming convention issue usually reflects the fact that GIS professionals with little cartography experience compiled the data for use in the Viewer. (If I seem to be nit-picking here it is because I build maps for a living using this same technology. I know these are issues that are easy to fix and should have been taken care of before the Viewer was opened up to the public.)
These shortcomings aside, the National Map Viewer is pretty darned good. I'd say the USGS gets a good solid 'B' for this effort. If they'd improve the damned printing issue I'd give them an 'A'.
It is a slightly dry film put out by the US Geological Survey in 1955 showing the modern (for the time) processes developed for natural resource analysis using aerial photography.
The guy narrating it sounds about as excited by his work as a dry goods salesman discussing the newest laundry soap. Zzzzzzzzz...
But once past the dry narration I was interested by the methods demonstrated for geological, hydrological, soils and forestry analysis. What struck me was that these were the precise methods we were taught at the Defense Mapping School as late as the early 1990s. These photo analysis processes formed the basis for what we called Terrain Analysis, and in fact my job title for much of my Army career was Terrain Analysis Technician (MOS 215D).
This film approaches each type of analysis as an independent process - an end in itself. We carried the analysis to the next level and merged the output from each of these four disciplines, mixed in some military-specific data like vehicle off-road capabilities, tossed in some road network analysis, some urban analysis and a pinch of weapon systems analysis and produced what we called a military terrain analysis. Our products were usually delivered in the form of map overlays known as a combined obstacle study. The process was very labor intensive and usually tightly focused on specific geographic areas like the Fulda Gap in Germany or the Koksan Bowl in Korea, natural movement corridors that had been used by armies for centuries.
Soldiers going into the Army's Terrain Analysis field received extensive training in field identification methods like geological and soils analysis, hydrological analysis and route engineering studies. They were taught to observe, test and measure in the field using a variety of hands-on methods. Next they moved to the classroom and were taught advanced aerial photo analysis techniques and applied their field knowledge to what they saw in the photos. It was hours and hours of peering at photos through stereoscopes, analyzing texture, tone and pattens to develop a detailed analysis of the terrain and it's impacts on military operations.
Computers have taken on the burden of much of this analysis, and today you can feed a digital image into a sophisticated image analysis package like ERDAS Imagine and have it analyze huge swaths of territory in a small fraction of the time it took using the old manual methods shown in the film. Still, it is fun to see how things were done in the good old days when men were men, hardhats were made out of aluminum and the science of aerial photo analysis found new applications in the civilian and military worlds.
Missed it by a day, but Happy Birthday to the US Geological Survey!
The USGS was established on 3 March 1879, almost as an afterthought in a Federal budget submittal. It's stated mission was "classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain."
The first part of that mission, "classification of the public lands," was what drove a lot of the USGS's early efforts. The US had acquired a lot of land as the result of the Louisiana Purchase and the Mexican War, but we didn't have a very good picture of just what it was we had gotten our hands on. The USGS launched a standardized mapping effort that continues to this day, and will never really be completed. Mapping the United States is like painting the Golden Gate Bridge, as soon as you finish at one end it's time to go back and start again at the other.
I'm hard pressed to name another federal agency that has done so much good work for both the nation as a whole and its citizens.
So here's the the US Geological Survey. Happy one hundred and thirty second birthday!
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.
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:
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.
