dblust
FNG
I’m a detective with the Sweetwater County Sheriff’s Office in Wyoming, and I’ve trained hundreds of fellow law enforcement officers, search and rescue teams, firefighters, and outdoor recreationists - especially hunters - in back country navigation over the course of the last two decades.
I’ve put on courses in Wyoming, Utah, Colorado, Montana, and Washington and will have a back country webinar completed soon. (In May, I’m teaching my one-day and two-day course in Evanston, Wyoming.)
I thought I’d reproduce here at Rokslide a number of posts related to back country navigation that appeared originally (in one form or another) at the website of Just Trails, headquartered in Laramie, Wyoming, and hope they will be found useful.
- Dick Blust, Rock Springs, Wyoming
______________________________
Before there was GPS, there was map and compass.
It is a misconception that GPS has replaced map and compass. Map and compass are an integral part of a comprehensive approach to effective, serious back country navigation with all three - map, compass, and GPS - working together in concert and, at the same time, backing each other up.
There are a lot of compasses out there on the market, and they range from the meticulously crafted to the downright useless. Fortunately, the best choices for the serious back country navigator can be boiled down considerably. The key factors are accuracy, precision, dependability, durability, utility, and night operation capability. I put special emphasis on night capability because if you spend enough time in the back country, you will not only need the skills and resources to navigate in the dark, it’s after dark when you will probably need them most.
In order of expense, my top choices are the M-73 or M-88 Francis Barker, both of which are prismatics, the Cammenga Model 3H or M27 lensatic, and the Silva Model 54 Expedition, which was once available as the Brunton Model 54 or 54LU.
The M-73 and M-88 Prismatic Compasses
The M-73 and M-88 prismatics are top of the line, and their price tags - about $450 for the M-73 and a hundred or so less for the M-88 - reflect it. The manufacturer, Pyser-SGI (www.pyser-sgi.com), is located in Kent in the United Kingdom. The M-73 weighs in at about 7.4 ounces. This is due to a lot of brass in its construction, plus it’s fluid-dampened. At 4.4 ounces, the M-88 is the lightweight version of the M-73 with less brass and more aluminum in the design. Otherwise, its features, accuracy, etc., are pretty much identical to those of the M-73.
Handheld without support, readings down to ½ degree are easily obtainable. Rested on a wooden hiking staff or other non-magnetic brace, such as aluminum hiking poles, readings can be taken down to 1/4 degree.
These British prismatics are the contemporary versions of what the Brits have been using, with constant improvement and refinement, since before the Boer War. Fitted with five tiny Tritium lamps, they are not only extremely accurate but are completely functional in even total darkness. Though pricey, they’re worth every nickel.
Note: There are many cheap knockoffs of these compasses in circulation, manufactured mostly in the Middle East. Exercise caution if you’re not buying yours directly from the manufacturer or a reputable dealer - especially if you’re considering one posted for sale on the Internet.:
Pros: Extremely accurate and precise, reliable, durable, top quality
Cons: Heavy, expensive
Model 3H / Model 27 United States Military Lensatic Compass
Manufactured since 1992 by Cammenga, (www.cammenga.com), this compass has been official American military issue for decades. The Model 3H is tritium-illuminated; the Model 27 is phosphorescent; otherwise, they are identical.
The phosphorescent M27 runs about $62.00, the 3H about $100. (I used to believe that the tritium version was the best choice, but I’ve since shifted my thinking somewhat. A compass that is tritium-illuminated is as bright as it’s ever going to be right out of the box, but a phosphorescent compass can always be brightened up with a good “flashlight shot.”)
The 3H/27 is a “dry card” compass, unlike the British M73 and M88 prismatics, which are fluid dampened. Older dry-card compasses had a drawback in that they took quite a while to settle down on a bearing, but the 3H/27 solves this problem with its Copper Induction Damping System, which is fast and very effective.
Somewhat uniquely, the 3H/27's compass card is graduated in both mils and degrees. (Just as there are 360 degrees in a complete circle, a complete circle in the mil system is represented by 6400 mils.) On the lensatic compass, the mil graduations appear in 20-mil increments; 20 mils is the equivalent of 1.125 degrees. On the other side of the equation, there are about 17.777 mils in a single degree, which the Army likes to round off at 17.8. (Mils are used by the military in artillery sighting and in optical rangefinders in rifle scopes.)
The Cammenga 3H/M27 lensatic compass is graduated in both mils and degrees with the degree graduations in 5-degree increments and the mil marks in 20-mil increments, as shown below.
Doing precision work with the rather coarse 5-degree scale is problematic, and while it’s true that with practice you can learn to estimate 1½-degree graduations with reasonable accuracy, there’s an option that I prefer for more exacting results - converting mils to degrees and vice versa, as necessary.
Under the mil system as employed in America, there are 6,400 mils (sometimes called angular mils) in a complete circle of 360 degrees. Hence there are 17.777 mils in one degree and one mil equals .05625 degrees.
North - 360 degrees / 6400 mils
East - 090 degrees / 1600 mils
South - 180 degrees / 3200 mils
West - 270 degrees / 4800 mils
The card of the Cammenga lensatic compass is graduated along its outer edge in mils in 20-mil increments, and taking sight readings in 10-mil increments is not difficult. Each 20-mil graduation equals 1.125 degrees, and 10 mils represents .5625 degrees, making the equivalent of single degree and even half-degree readings readily accomplished.
The formula is as follows:
- To convert mils to degrees, multiply the number of mils x .05625.
- To convert degrees to mils, multiply the number of degrees x 17.777
A small calculator is what makes doing the conversions practical. Let’s say you take a sighting on a prominent peak, and it’s 2,120 mils. To convert to degrees, multiply the 2,120 mils x .05625 to arrive at a figure of 119.25 - 119.25 degrees (or 119 degrees, 15 seconds.)
If, working with degrees, you plot a course leg or baseline to (or toward) a landmark or a steering mark, (let’s say 150 degrees), multiply the degrees (in this example, 150) x 17.777 to arrive at a figure of 2,666.55, which rounds off to 2,670 mils.
I prefer the “do the math” option to estimating 1½-degree increments on the degree scale because of the precision it offers. Once you’ve practiced with it a bit, it becomes second nature.
The other shortcoming is that the 3H/27 it is a bit more difficult to use at night than the prismatic M88/M73 and Silva 54. That said, the 3H/is extremely durable and accurate. At 5.3 ounces - it’s made of aluminum - it’s also quite light.
Note: There seems to be an endless supply of lame lensatic compasses on the market running from $10 to $25 or so. Avoid these. If you want a lensatic, do yourself a favor and stick with the real thing made by either Cammenga or Stocker & Yale, bearing in mind that the tritium illumination of a Stocker & Yale is apt to be pretty much faded out due to its age.
Pros: Accurate, reliable, robust, reasonably light, reasonably priced
Cons: A bit tougher to use at night. Using mils provides excellent precision, but requires application of a little math for good map work.
Silva Expedition Model 54 Compass
An extremely clever, reliable, and accurate design that combines precise prismatic sight readings - down to ½ of a degree - with the light weight and utility of a baseplate orienteering compass, all for about $100 or a little less; that’s the Silva Expedition Model 54, shown below.
Note some of its features: a magnifier, 1:25,000, 1:50,000, and 1:63,360 UTM corner scales, and two rulers. (An explanation is in order here, as the compass shown is clearly marked “Brunton.” At one time, Brunton marketed the Model 54 here in the U.S., but has ceased doing so. Fortunately, it’s still available in the United Kingdom under its original designation, the Expedition Model 54, and is exactly identical to the former Brunton version.)
The Model 54 is phosphorescent; at night, you have to give it a “flashlight shot” from time to time, but once you’ve done that, it’s very bright and easy to read, as the image below shows. (This shot was taken in total darkness.)
There are other night-friendly compasses on the market made by Silva, Suunto, and others, but I’ve used these three extensively and recommend them highly for hunters.
I'd be remiss if I didn't make an observation here. It is often the case with equipment that cheaper means poorer quality, but that is not so here. The Silva Expedition represents an ingenious design that is multi-functional yet extremely light in weight [about 1.4 ounces] - a great instrument. If I were starting from scratch today, I'd go with this one.
Pros: Light, precise, accurate, multi–functional.
Cons: Hard to think of any.
I’ve put on courses in Wyoming, Utah, Colorado, Montana, and Washington and will have a back country webinar completed soon. (In May, I’m teaching my one-day and two-day course in Evanston, Wyoming.)
I thought I’d reproduce here at Rokslide a number of posts related to back country navigation that appeared originally (in one form or another) at the website of Just Trails, headquartered in Laramie, Wyoming, and hope they will be found useful.
- Dick Blust, Rock Springs, Wyoming
______________________________
Choosing a Compass
Before there was GPS, there was map and compass.
It is a misconception that GPS has replaced map and compass. Map and compass are an integral part of a comprehensive approach to effective, serious back country navigation with all three - map, compass, and GPS - working together in concert and, at the same time, backing each other up.
There are a lot of compasses out there on the market, and they range from the meticulously crafted to the downright useless. Fortunately, the best choices for the serious back country navigator can be boiled down considerably. The key factors are accuracy, precision, dependability, durability, utility, and night operation capability. I put special emphasis on night capability because if you spend enough time in the back country, you will not only need the skills and resources to navigate in the dark, it’s after dark when you will probably need them most.
In order of expense, my top choices are the M-73 or M-88 Francis Barker, both of which are prismatics, the Cammenga Model 3H or M27 lensatic, and the Silva Model 54 Expedition, which was once available as the Brunton Model 54 or 54LU.
The M-73 and M-88 Prismatic Compasses
The M-73 and M-88 prismatics are top of the line, and their price tags - about $450 for the M-73 and a hundred or so less for the M-88 - reflect it. The manufacturer, Pyser-SGI (www.pyser-sgi.com), is located in Kent in the United Kingdom. The M-73 weighs in at about 7.4 ounces. This is due to a lot of brass in its construction, plus it’s fluid-dampened. At 4.4 ounces, the M-88 is the lightweight version of the M-73 with less brass and more aluminum in the design. Otherwise, its features, accuracy, etc., are pretty much identical to those of the M-73.
Handheld without support, readings down to ½ degree are easily obtainable. Rested on a wooden hiking staff or other non-magnetic brace, such as aluminum hiking poles, readings can be taken down to 1/4 degree.
These British prismatics are the contemporary versions of what the Brits have been using, with constant improvement and refinement, since before the Boer War. Fitted with five tiny Tritium lamps, they are not only extremely accurate but are completely functional in even total darkness. Though pricey, they’re worth every nickel.
Note: There are many cheap knockoffs of these compasses in circulation, manufactured mostly in the Middle East. Exercise caution if you’re not buying yours directly from the manufacturer or a reputable dealer - especially if you’re considering one posted for sale on the Internet.:
Pros: Extremely accurate and precise, reliable, durable, top quality
Cons: Heavy, expensive
Model 3H / Model 27 United States Military Lensatic Compass
Manufactured since 1992 by Cammenga, (www.cammenga.com), this compass has been official American military issue for decades. The Model 3H is tritium-illuminated; the Model 27 is phosphorescent; otherwise, they are identical.
The phosphorescent M27 runs about $62.00, the 3H about $100. (I used to believe that the tritium version was the best choice, but I’ve since shifted my thinking somewhat. A compass that is tritium-illuminated is as bright as it’s ever going to be right out of the box, but a phosphorescent compass can always be brightened up with a good “flashlight shot.”)
The 3H/27 is a “dry card” compass, unlike the British M73 and M88 prismatics, which are fluid dampened. Older dry-card compasses had a drawback in that they took quite a while to settle down on a bearing, but the 3H/27 solves this problem with its Copper Induction Damping System, which is fast and very effective.
Somewhat uniquely, the 3H/27's compass card is graduated in both mils and degrees. (Just as there are 360 degrees in a complete circle, a complete circle in the mil system is represented by 6400 mils.) On the lensatic compass, the mil graduations appear in 20-mil increments; 20 mils is the equivalent of 1.125 degrees. On the other side of the equation, there are about 17.777 mils in a single degree, which the Army likes to round off at 17.8. (Mils are used by the military in artillery sighting and in optical rangefinders in rifle scopes.)
The Cammenga 3H/M27 lensatic compass is graduated in both mils and degrees with the degree graduations in 5-degree increments and the mil marks in 20-mil increments, as shown below.
Doing precision work with the rather coarse 5-degree scale is problematic, and while it’s true that with practice you can learn to estimate 1½-degree graduations with reasonable accuracy, there’s an option that I prefer for more exacting results - converting mils to degrees and vice versa, as necessary.
Under the mil system as employed in America, there are 6,400 mils (sometimes called angular mils) in a complete circle of 360 degrees. Hence there are 17.777 mils in one degree and one mil equals .05625 degrees.
North - 360 degrees / 6400 mils
East - 090 degrees / 1600 mils
South - 180 degrees / 3200 mils
West - 270 degrees / 4800 mils
The card of the Cammenga lensatic compass is graduated along its outer edge in mils in 20-mil increments, and taking sight readings in 10-mil increments is not difficult. Each 20-mil graduation equals 1.125 degrees, and 10 mils represents .5625 degrees, making the equivalent of single degree and even half-degree readings readily accomplished.
The formula is as follows:
- To convert mils to degrees, multiply the number of mils x .05625.
- To convert degrees to mils, multiply the number of degrees x 17.777
A small calculator is what makes doing the conversions practical. Let’s say you take a sighting on a prominent peak, and it’s 2,120 mils. To convert to degrees, multiply the 2,120 mils x .05625 to arrive at a figure of 119.25 - 119.25 degrees (or 119 degrees, 15 seconds.)
If, working with degrees, you plot a course leg or baseline to (or toward) a landmark or a steering mark, (let’s say 150 degrees), multiply the degrees (in this example, 150) x 17.777 to arrive at a figure of 2,666.55, which rounds off to 2,670 mils.
I prefer the “do the math” option to estimating 1½-degree increments on the degree scale because of the precision it offers. Once you’ve practiced with it a bit, it becomes second nature.
The other shortcoming is that the 3H/27 it is a bit more difficult to use at night than the prismatic M88/M73 and Silva 54. That said, the 3H/is extremely durable and accurate. At 5.3 ounces - it’s made of aluminum - it’s also quite light.
Note: There seems to be an endless supply of lame lensatic compasses on the market running from $10 to $25 or so. Avoid these. If you want a lensatic, do yourself a favor and stick with the real thing made by either Cammenga or Stocker & Yale, bearing in mind that the tritium illumination of a Stocker & Yale is apt to be pretty much faded out due to its age.
Pros: Accurate, reliable, robust, reasonably light, reasonably priced
Cons: A bit tougher to use at night. Using mils provides excellent precision, but requires application of a little math for good map work.
Silva Expedition Model 54 Compass
An extremely clever, reliable, and accurate design that combines precise prismatic sight readings - down to ½ of a degree - with the light weight and utility of a baseplate orienteering compass, all for about $100 or a little less; that’s the Silva Expedition Model 54, shown below.
Note some of its features: a magnifier, 1:25,000, 1:50,000, and 1:63,360 UTM corner scales, and two rulers. (An explanation is in order here, as the compass shown is clearly marked “Brunton.” At one time, Brunton marketed the Model 54 here in the U.S., but has ceased doing so. Fortunately, it’s still available in the United Kingdom under its original designation, the Expedition Model 54, and is exactly identical to the former Brunton version.)
The Model 54 is phosphorescent; at night, you have to give it a “flashlight shot” from time to time, but once you’ve done that, it’s very bright and easy to read, as the image below shows. (This shot was taken in total darkness.)
There are other night-friendly compasses on the market made by Silva, Suunto, and others, but I’ve used these three extensively and recommend them highly for hunters.
I'd be remiss if I didn't make an observation here. It is often the case with equipment that cheaper means poorer quality, but that is not so here. The Silva Expedition represents an ingenious design that is multi-functional yet extremely light in weight [about 1.4 ounces] - a great instrument. If I were starting from scratch today, I'd go with this one.
Pros: Light, precise, accurate, multi–functional.
Cons: Hard to think of any.
Last edited:
