It's been a while since we looked at the merits and shortcomings of specific compass designs. Over the past six months or so I've been testing and evaluating a number of handheld compasses from various manufacturers. It has been something of a grail quest, searching for the perfect compass. Along the way I've learned a lot about compass design, accuracy and usability. In the next series of postings we'll discuss specific compasses and perhaps help you select a compass for your needs. Not all of what I evaluated were modern compasses; I've included a few examples in this evaluation that were manufactured over 60 years ago and represent designs that go back over 100 years.
Before we get started let me state that there is no such thing as the perfect compass. No one design can meet all needs. The best approach in compass selection is to pick the design that best meets the needs of the job at hand. If you are running an orienteering course you'll probably want to pick a compass specifically designed for that sport. However, if you are doing serious backwoods land navigation you'll want a direct reading compass that can give accurate azimuths to within 1/2 of a degree. On the other hand, if you are a geologist doing stratigraphic mapping you'll need a compass that will also allow you to measure the strike and dip of rock formations. Always pick the tool that best suits the task at hand.
Over the next series of postings in the Which Way North series I'll evaluate specific compasses on the following criteria:
1. Basic Design - How good is the basic design of the compass, particularly if the compass was designed for a specific function? How well does the design meet the stated goal?
2. Features - Are any added features (luminous markings, baseplate scale markings, built-in clinometers, etc.) useful and do they add to the functionality of the compass?
3. Execution - Did the manufacturer do a good job building the compass?
4. Usability - How easy is it to use the particular compass in the real world?
6. Accuracy - How accurate is the compass (in degrees) when used as it was designed and intended to be used?
Much of this evaluation will be subjective. After all, it is my blog so I set the rules. However, my subjective evaluation is based on over 40 years of compass use as a geologist, topographer and Army engineer officer. I may be a bit subjective in my evaluation, but it is a well honed subjectivity.
Other things you should understand about my evaluation criteria are:
1. I value accuracy above all else. If a compass is not accurate (within it's design parameters) then it is a piece of junk. I don't care who made it or how expensive it was, if it ain't accurate it's junk. I think it is important to understand how I evaluate accuracy. I have access to an azimuth station where I test all my compasses for accuracy. An azimuth station is a site where survey points have been established and the precise azimuths between points (in relation to true north) is established. Each compass is checked against three points each roughly 90 degrees apart. All are checked for handheld accuracy and if possible, supported accuracy when mounted on a jacob staff. Each compass is tested three times in each mode and the magnetic azimuth results averaged. The averaged result is then adjusted for local declination (as determined by NOAA) and checked against the known azimuths between each of the survey points. The difference between the surveyed azimuth and the adjusted magnetic azimuth is the compass accuracy.
2. Ruggedness of design is next on my list of criteria. A compass that is marketed for outdoor use should be able to withstand that use and deliver reliable and accurate service. I'm not saying that we should expect to use a compass as a substitute hammer, but it is not unreasonable to expect a land navigation compass to easily withstand the normal bumps and shakes that come with being used out of doors.
3. Declination. A lot of compasses have adjustable declination scales. I do not consider the presence or absence of an adjustable declination scale of any particular importance. In my opinion adjusting for declination on the compass gives a false sense of security. There are far too many variables in the declination equation to allow it to be handled by a coarse declination scale built into a handheld compass. However, an adjustable declination scale can be useful for another purpose - adjusting out any error built into a particular compass or compass design.
4. You rarely use the compass all by itself so consider it part of a land navigation kit. This kit should also include maps of the area you are working in, a plotting scale and a notebook and pencil. All my evaluations are done in consideration of the compass as part of this kit.
Also keep in mind that I didn't test every compass available. My schedule (and wallet) won't allow that. However, I did obtain the most common examples available from the major manufacturers like Silva, Suunto, Brunton, K&R and a few others. If you have interest in a particular model or style let me know. I may already have it on my list for evaluation or may be able to get an example to test.
So stay tuned for the plain truth on compasses!
Brian
Showing posts with label land navigation. Show all posts
Showing posts with label land navigation. Show all posts
Saturday, April 23, 2011
Sunday, March 20, 2011
The Wilderness Route Finder
I grew up reading - devouring, really - the works of two great outdoor writers. One was Brad Angier and the other was Calvin Rutstrum. These two adventurers had been living the 'back to nature' lifestyle long before the backpacking craze hit America in the 1960s. Both were prolific writers, turning out books and papers that extolled the wilderness lifestyle. Angier's works were more philosophic - he fancied himself a modern day Thoreau and his books reflected that outlook. Rutstrum, on the other hand, didn't just live the wilderness lifestyle, he actually worked in and made a living from the wilderness, primarily through guiding. Rutstrum's advice was always more down to earth, more practical.
Some of Rutstrum's advice would cause modern day enviroweenies to fall over in a dead faint. For example, to deal with the biting insects that invariably got into your tent when camping in the north country Rutstrum recommended just tossing a DDT 'bomb' (spray canister) into the tent, zipping it up and letting the insecticide do its job. Go off and do your chores and when you come back you'll have a bug-free tent to sleep peacefully in. Keep in mind, however, that Rustrum's books were written from the late 1940s through the 1970s, so some procedures and 'best practices' are now out-dated and in many cases downright illegal. Regardless, his books like 'New Way of the Wilderness' and 'Paradise Below Zero' are still considered classics of outdoor literature.
Another gem that Rutstrum wrote is 'The Wilderness Route Finder'.
I first came across this book over 30 years ago and read it cover to cover multiple times. I believe it is the first broad application land navigation work written for the general public. (The Army land navigation field manual, FM 21-26, pre-dates this work by several decades. While an excellent work is targeted at military users.) Rutstrum approached land navigation the way he approached so many things related to the outdoors - use what works. He presents a broad range of techniques and discusses use of a number of pieces of equipment that can assist in navigating the high latitudes where the magnetic compass becomes unreliable due to declination issues and local magnetism.
Obviously this book was written before GPS was even a gleam in the eye of senior military commanders, and many of the pieces of equipment Rutstrum discusses are out dated or simply not available anymore. For example, cruiser compasses have not been made for decades and have now entered the status of collector's item. However, some of the techniques he discusses, while at first glance seemingly archaic in the world of cell phones, wireless internet and GPS, are still valid and those serious about land navigation ought to give them a try. For example, the concept of using a marine sextant to determine latitude is quite valid, and quality used sextants are available today for less than $400. Equip one with a bubble horizon and bring along a quality quartz watch and you could even do reasonably accurate longitude determination. Think of it as an exercise in confidence building.
The reader should be aware that Rutstrum wrote this book specifically for those navigating in the far north regions of the US and Canada. There is little in this book about desert or tropical environments. Rutstrum was also a man of his time and wrote like it. Many of the explanations are a little wordy and personal pronouns are few and far between. Keeping in mind these shortcomings, the book is still an undisputed classic and belongs on the shelf of anyone serious about learning land navigation.
Brian
Some of Rutstrum's advice would cause modern day enviroweenies to fall over in a dead faint. For example, to deal with the biting insects that invariably got into your tent when camping in the north country Rutstrum recommended just tossing a DDT 'bomb' (spray canister) into the tent, zipping it up and letting the insecticide do its job. Go off and do your chores and when you come back you'll have a bug-free tent to sleep peacefully in. Keep in mind, however, that Rustrum's books were written from the late 1940s through the 1970s, so some procedures and 'best practices' are now out-dated and in many cases downright illegal. Regardless, his books like 'New Way of the Wilderness' and 'Paradise Below Zero' are still considered classics of outdoor literature.
Another gem that Rutstrum wrote is 'The Wilderness Route Finder'.
 |
| My copy, purchased in the late1970s and well thumbed |
I first came across this book over 30 years ago and read it cover to cover multiple times. I believe it is the first broad application land navigation work written for the general public. (The Army land navigation field manual, FM 21-26, pre-dates this work by several decades. While an excellent work is targeted at military users.) Rutstrum approached land navigation the way he approached so many things related to the outdoors - use what works. He presents a broad range of techniques and discusses use of a number of pieces of equipment that can assist in navigating the high latitudes where the magnetic compass becomes unreliable due to declination issues and local magnetism.
Obviously this book was written before GPS was even a gleam in the eye of senior military commanders, and many of the pieces of equipment Rutstrum discusses are out dated or simply not available anymore. For example, cruiser compasses have not been made for decades and have now entered the status of collector's item. However, some of the techniques he discusses, while at first glance seemingly archaic in the world of cell phones, wireless internet and GPS, are still valid and those serious about land navigation ought to give them a try. For example, the concept of using a marine sextant to determine latitude is quite valid, and quality used sextants are available today for less than $400. Equip one with a bubble horizon and bring along a quality quartz watch and you could even do reasonably accurate longitude determination. Think of it as an exercise in confidence building.
The reader should be aware that Rutstrum wrote this book specifically for those navigating in the far north regions of the US and Canada. There is little in this book about desert or tropical environments. Rutstrum was also a man of his time and wrote like it. Many of the explanations are a little wordy and personal pronouns are few and far between. Keeping in mind these shortcomings, the book is still an undisputed classic and belongs on the shelf of anyone serious about learning land navigation.
Brian
Sunday, December 12, 2010
Book Of The Month for December 2010 - '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.
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.
Subscribe to:
Posts (Atom)