Tuesday, December 16, 2008
Wednesday, November 19, 2008
M Kelly, R Gagne, JD Newman, C Olney, C Gualtieri, D Trail
The objective was to design a protocol to assess work ability in people suffering ill-defined painful and disabling disorders, the outstanding prototype of which is fibromyalgia/chronic fatigue syndrome (FM/CSF).Following an extensive literature search, the most appropriate components of current methods of assessment of physical and cognitive abilities were incorporated into the protocol, occasionally with appropriate modification to suit the specific requirements of the individual.
The initial part of the assessment consists of a standard history taking, principally focusing on the patient’s self-reported physical and cognitive abilities and disabilities, as well as the completion of established pain and fatigue scales, and relevant disability questionnaires.
Following this, physical and cognitive abilities are objectively assessed on two separate occasions, utilizing computerized hand-held dynamometers, inclinometers, algometers, and force dynamometers. Specific work simulation tests using the industrial standards Methods-Time-Measurement testing are availed of, as is aerobic testing using the Canadian Aerobic Fitness Test (CAFT).
Objective computerised neuro-cognitive testing are also utilised as an integral component of the assessment. All results are then subject to specific computerized analysis and compared to normative and standardised work-based databases. The designed system produces reliable, consistent and reproducible results.
It also proves capable of detecting any inconsistencies in patient input and results, in addition to being independent of any possible assessor bias. A new protocol has been designed to determine the working capability of individuals who suffer from various chronic disabling conditions, and represents a significant step forward in a difficult but rapidly expanding area of medical practice.
Tuesday, November 18, 2008
Story Published: Nov 14, 2008 at 6:31 PM PST
Highway 169 is closed at the Green River bridge. But the state just spent a lot of money fixing the bridge.
The bridge gives the state heart burn and motorists heartache. Twice this year - twice within six months - the bridge has been closed because of landslides.
The first slide in June broke some big chunks of concrete loose. The state closed the bridge, brought in experts and drilled holes to find out why the earth was moving.
The state installed hillside drains. They reinforced walls. They put in inclinometers -- a fancy word for a device that will say if the bridge is leaning, which is not a good thing when you are 145 feet above the Green River.
"We've got three tilt meters under the bridge. We have several piezometers to help us measure the ground water," said Bob Grandoff with the Department of Transportation.
No one was too worried.
Then it rained this week. Water flowed out of the hillside. Despite all the stabilization, those tilt meters recorded a very slight movement.
"Any time a bridge is moving, I think it is prudent to close the road for safety, of course," said Grandoff said.
The bridge was closed.
In the closest town, Black Diamond, those closures make some nervous:
"I go really fast and I say it's my last time every time," said Katie Doyle.
"How can they sink concrete down that far to stabilize it?" said Marilyn Pedersen.
The state says Doyle, Pedersen and the rest of you need not worry. The bridge is safe and they'll do whatever is necessary to keep it that way.
"Right now, it is the most watched bridge in the state," said Grandoff.
This bridge is constantly monitored. Radio signals go to DOT officials Olympia. With even the slightest movement, the bridge gets shut down.
Right now there is no movement; there doesn't seem to be a problem. But the state says the signals must show no problems for at least 48 hours before they will reopen the bridge. That could happen this weekend.
As I always say, better safe than sorry - inclinometers continuously prove value as added levels of safety monitoring and warning for critical, potentially life threatening tilt applications - Skip Gosnell
Monday, November 17, 2008
12 November 2008Posted by volcanism in Colombia, Machín, activity reports.
The alert level at Colombia’s Cerro Machín volcano remains at a cautious level III, yellow (where level I, red, is the highest), but INGEOMINAS Observatorio Vulcanológico y Sismológico de Manizales reports ‘normality’ in the volcano’s activity and a decrease in seismicity in its latest bulletin (dated 11 November 2008):
During 8, 9 and 10 November the volcano Cerro Machín registered a seismic event within which 1210 volcano-tectonic earthquakes were recorded (associated with the fracturing of rock in the interior of the volcano), 9 of which were with magnitudes greater than 2.5, several being heard by the inhabitants of Cajamarca, Ibagué, Calarcá and Armenia, among others.
The inclinometers located around the volcano showed significant changes, associated with the principal event of 9 November at 03:01.
On 9 November an INGEOMINAS commission went to the volcano Machín with the aim of evaluating conditions at the volcano. The report submitted is of complete normality in the activity of the volcano, the cracking of some houses and landslides caused by seismic movement, associated with ground conditions of high humidity.
From 10:00 yesterday, Monday 10 November, the seismic activity of the volcano decreased notably and at the time of publication of this communication the levels of seismic activity are low.
The tremors and ashfall of Sunday and Monday produced great alarm among local populations but also, reports La Patria, ’strengthened the solidarity of the community’. Some 500 people from farming communities around Cerro Machín who fled their homes are being accommodated in Ibagué, in a relief operation co-ordinated by the Red Cross. Local residents are helping to provide food and other supplies for the refugees. The recent activity from Machín and Nevado del Huila volcanoes, writes El País, ‘holds half the country in suspense’. Perhaps it will raise awareness of the potential dangers posed by Colombia’s volcanoes, which may well be needed: last week, reports El Tiempo, INGEOMINAS held a community emergency training event for the residents of areas around Machín, ‘but no-one attended’.
Monday, October 20, 2008
|By: Ambrosia Sarabia | Wednesday, October 15, 2008 10:40:00 AM|
|Last updated: Wednesday, October 15, 2008 10:40:00 AM|
“I’m really trying to take the fear and the mystery out of the unknown,” explained Paul DeCapua, an assistant sail fleet captain for Bahia Corinthian YC.
The seminars began last year, in an effort to promote racing. After thinking back to his early days of racing and how confusing it could be for a newcomer, DeCapua decided to lead the seminars.
Back then, “I had no clue what to do,” said DeCapua, who followed the leaders around the marks not knowing what was right or wrong. “What may slow folks down is that they don’t know what to do.”
Now, with more than 15 years of sailing experience under his belt, he is determined to help nonracers make the transition to become experienced racers.
Boaters from local yacht clubs and nonmembers both participated in the seminar, where they received handouts listing the Rules of the Road and information on how to knock seconds off their time. Those who stayed for both lectures (which was everyone) received free entry into the Hot Rum Series at the yacht club.
For those more experienced racers, part two of the seminar — Sailboat Racing 102 — offered tips on how to shave valuable seconds off racing times. Suggestions included strategies for optimum crew placement, sail trim, rigging and crew work.
Other tips included using lightweight sheets in light wind, removing unnecessary clutter from a vessel and installing sail telltales and an inclinometer.
Ward Adams, a resident of Lido Peninsula, said he is going to put some of those tips to work.
“I learned a lot of rigging tips, sail-trimming tips and advice on how to position the crew,” said Adams, a Beneteau owner. “All of it was very helpful.”
For more information on seminars, visit www.bcyc.org.
Thursday, August 14, 2008
-interestingly enough, an inclinometer (a device used to indicate tilt or slope in reference to gravity) and has been around since the early 1900's, is quite often used for roll over prevention in bucket trucks and other aerial lift equipment.
Monday, July 14, 2008
By BRYAN FRENCH
When it’s not hunting season, what’s a hunter to do?
Hunt for stuff.
Many hunting enthusiasts take to the summer hunting grounds of their favorite outdoors superstore when they can get away, some spending hours browsing, testing, looking at all that gear they could use this fall and winter.
Here’s a look at four of the most popular buys in the gear hunting season:Range finders
will probably want a unit with an inclinometer, for true horizontal range.
Monday, July 07, 2008
RAND BLANC, Mich. - If Doug LaBelle II doesn’t hit any of his approach shots close to the pin during his morning practice round for the Buick Open, don’t worry. He’ll actually be missing on purpose.
That’s because the PGA Tour pro from Mt. Pleasant, Mich., and his caddie, Duane Bock, have a strategy in mind. The pair will be envisioning the pin locations from the first round of last year’s tournament.
"Just trying to find out where you need to put the ball based on where the hole location is and what the hole does," LaBelle said Monday on the practice range. "Basically, what club to hit off each tee."
It’s part of the process of preparation players and caddies go through before each tournament. It’s sort of the tournament before the tournament.
Monday at Warwick Hills Golf and Country Club, caddies practically outnumbered fans. Caddies usually are the first to arrive at the course. They pick up a yardage book that has been meticulously prepared by a veteran caddie. The book contains drawings of each hole and almost every imaginable yardage from the landing zones for drives, lay-up shots, chipping areas and the contours of greens.
But caddies such as Bock still have to double check those yardages. That means plenty of reconnaissance work. Bock arrived at Warwick Hills at 6:30 a.m. Monday and spent the next five hours writing copious notes in his yardage book. Despite the detail already provided in the book, Bock used a laser rangefinder to check elevation changes, carry yardages over hazards, and he also made note of wind direction.
"I honestly believe that my main job as a caddie is to provide information," said Bock, who used to play on the Canadian Tour with LaBelle. "And if I’m prepared with all my information, no matter what question he asks _ ’What is it to this point, to that point?’ _ I’m going to have it in my notes somewhere so I can tell him confidently, ’Hey, we have 130 (yards) to carry that bunker right there.’ So when he stands over it he has no doubts in his mind."
LaBelle is a precise player who prides himself on his course management. LaBelle even carries his own inclinometer to check elevations himself. But even LaBelle messes up once in a while.
That’s when JICYFU comes into play.
JICYFU is an acronym written into a yardage book that stands for Just In Case You _ well, you get the drift. The areas marked "JICYFU" in the yardage book designate yardages to the green for drives that have been sprayed left or right, where sprinkler heads aren’t available.
"Hopefully we don’t have to use those," LaBelle and Bock said in unison.
Of course, not all players and caddies fit the same mold. Woody Austin, the 1995 Buick Open winner who is playing the tournament for the 14th time, prefers a more straightforward approach. When he and his caddie, Brent Henley, played nine practice holes Monday morning, it was only to get a feel for any changes to the course.
"That’s too technical for me," Austin said of dissecting yardage books and using laser instruments. "When I go out and play tomorrow, tomorrow is just to see if anything’s different than what it’s been in the past.
"I try to be as simple as possible. I thoroughly believe there’s paralysis by analysis and there’s too much information. You get too much information, you forget how to play."
Tuesday, May 13, 2008
Now this is really cool!
Monday, May 05, 2008
May 1, 2008 on 11:02 am | In Neck Pain |
Clinimetric evaluation of active range of motion measures in patients with non-specific neck pain
Neck pain is a common musculoskeletal disorder. The incidence of neck pain in the Netherlands has been estimated as 23.1 per 1,000 person years. In general, women have more neck pain than men. In the Netherlands, 51% of patients with acute non-specific neck pain who consulted their general practitioners were referred to physiotherapists for treatment.
Neck pain may result from many causes (trauma, infections or inflammatory conditions, rheumatic disorders and congenital diseases), but most often no specific cause can be found and the condition is labelled as non-specific neck pain. In their clinical examination, physiotherapists and other healthcare providers may routinely perform an assessment of the active cervical range of motion (active neck range of motion ) to assess the level of impairment associated with neck pain as well as the results of treatment. Typical active neck range of motion assessments of the cervical spine include flexion and extension in the sagittal plane, lateral flexion in the frontal plane and rotation in the transverse plane. Tests or instruments which are used to examine active neck range of motion in patients with non-specific neck pain should meet several clinimetric prerequisites, such as an acceptable level of reproducibility, validity and responsiveness.
Recently, several systematic reviews have been published on the assessment of passive cervical range of motion and palpation procedures of the cervical spine. Among the palpation procedures, pain provocation tests were found to be the most reliable and the assessment of regional passive cervical range of motion instrument was found to be more reliable than segmental passive cervical range of motion instrument. However, in these reviews it was also concluded that most studies were of a poor methodological quality.
In 2000, a review was published that assessed the reliability of tools used to measure active neck range of motion . This review concluded that the cervical range of motion device has shown promising reliability. Our overview takes account not only of reliability, but also of validity and responsiveness.
The objective of the present systematic review, therefore, is to provide an overview of the current knowledge on clinimetric properties of instruments that are practical to use when evaluating active neck range of motion in patients with non-specific neck pain.
The present review provides information for researchers and clinicians to facilitate choice amongst existing instruments for measuring active neck range of motion . A systematic computerized literature search of databases revealed three different types of instruments that are practical to use when measuring active neck range of motion in patients with non-specific neck pain: visual estimation, tape measurements, different types of goniometers/inclinometers. When a healthcare professional decides that measuring active neck range of motion on a patient with non-specific neck pain is necessary, a single inclinometer and cervical range of motion instrument are to be recommended based on their best ratings for clinimetric properties and practicality. Visual estimation should not be used to measure active neck range of motion.
Friday, April 25, 2008
Strolling around the annual Australian Toy and Hobby Fair at the Melbourne Exhibition Centre last week, I was struck by how trends in the video game industry are influencing the toy market.
For example, it is hard to find an electronic pet product that now doesn't connect to an online world with your own customisable avatar. One of the latest is the ME2, which has a colour LCD screen and includes a built-in pedometer that lets you earn points redeemable online for every step you take.
The popularity of the Wii and Nintendo DS has certainly not gone unnoticed by toymakers. VTech's V-Motion has a motion-sensitive wireless controller, as does the Ulti-Motion from Jakks Pacific, and even Funtastic's Tri-Bot, from the makers of Robosapien, has a Wii-style tilt sensor for controlling the robot.
Thursday, April 24, 2008
Tuesday, April 15, 2008
Eric Milne is electrical and software chief engineer at Hydril. Reach him at email@example.com.
As industrial accidents go, a blowout in offshore natural gas or oil exploration surely ranks among the worst. When not contained, a blowout can release high pressure gasses that are frequently toxic and flammable, resulting in environmental damage and possible fatalities. Keeping a lid on these events requires a combination of the right hardware and control strategy.
Offshore drilling is a complex process. A drill pipe or drill string extends from the drilling rig down thousands of feet to the wellhead and into the wellbore on the sea floor directly beneath. This drill string is contained within a riser, or solid casing, to create an enclosed space. Inside the riser is drilling mud, a fluid mixture whose sheer weight is intended to contain any upsurge from the highly pressurized formations that are the ultimate target.
But sometimes the "kick" from the newly released hydrocarbons can literally push the drilling mud up the drill string and riser. If not blocked by heavier mud or stopped by a pressure control system, the oil or gas can rush up the pipe and emerge like a geyser on top of the rig. This is a blowout, and on something as small as a drilling platform, it is a disaster.Containing blowouts
Thankfully, blowouts are rare today. This stems in large part from the emergence of sophisticated and robust pressure control devices called blowout preventers (BOPs), controlled by real-time computing networks. Hydril LLC invented the first hydraulically operated BOP as well as the annular BOP, which features an opening lined with high-strength rubber that narrows or widens to control oil or gas flow.
Hydril's reputation for such inventions goes back into the 1930's, and still today the company is a leader in the design and manufacture of BOPs and drilling control systems. Hydril products are used worldwide, at drilling sites with the most extreme environments in terms of depth and wellbore pressure and temperature.
One major development goal has been to provide multiple levels of backup protection. Current designs achieve this by integrating three separate software disciplines - real-time operating systems (RTOSs), embedded high-availability database systems, and enterprise-style SQL server database management - into a single control system.
The enterprise database, Microsoft's SQL Server, lives on the rig and is used for archiving, reporting and troubleshooting functions. The embedded database, McObject's eXtremeDB High Availability, runs on QNX's Neutrino RTOS within the individual controllers, both on the rig and subsea, and provides duplicate "working copies" of data to support real-time processes.
Hydril's objective is to produce the safe and reliable BOPs and drilling control systems for the industry. The real risk takers are the specialist contractors who do exploratory drilling to determine whether or not there is a resource worth extracting. The initial drilling is critical since, much less is known about what's underground, and surprises can be greatest. These contractors are the most concerned about having failsafe solutions should the oil or gas within the wellbore deliver an unanticipated kick.
A pressure control system's key hardware is the BOP, which is essentially a large, heavy valve to contain pressure. A system will use multiple, specialized BOPs, configured in a vertical stack that sits on top of the well head. Above the stack are redundant BOP control pods, each consisting of a lower unit containing hydraulics to control the BOPs, and an upper electronics housing (EH). The EH is contained in a three-inch thick steel domed container to protect sensitive electronics gear from the surrounding water pressure. The pod also controls solenoids that operate hydraulic valves on the BOP.Drilling a complex process
During operation, each redundant Pod continuously gathers data from remote sensors, including:
Temperature and pressure in the wellbore - Obviously it is very cold at depths of 10,000 feet, but the energy used in drilling can generate temperatures as high as 82-176 °C (180 - 350°F) or higher. Sensors in the wellbore capable of measuring both high temperatures and high pressures monitor pressure spikes to help predict and control kicks.
Positioning - The stack should remain vertical, with the riser extending straight to the surface, but environmental conditions and positioning of the drilling vessel can make this a challenge. A KVH fiber optic gyro within the pod's electronics housing monitors stack rotation, while inclinometers measure tilt. If the riser is in an unacceptable position with regards to either the stack or the surface vessel, a dynamic positioning system on the rig corrects the problem.(for the rest of the article click here)
Friday, April 04, 2008
2009 Shimano Dura-Ace revealed
The electronic version promises much faster shifting than even the mechanical Dura-Ace version. (James Huang)
Shimano is expected to introduce two new Dura-Ace road racing component groups for 2009, one electronic and one fully mechanical. Highlights include carbon and titanium sub-components for reduced weight; improved braking and shifting, a wider choice of gearing and of course that electronic shift system.
The details of Shimano’s next generation of Dura-Ace road racing components have become one of the worst-kept secrets in the industry. Lots of seemingly accurate information has become available from industry sources. It’s safe to say that the beans have been spilled.
However, Shimano still will not officially confirm or deny anything regarding new Dura-Ace components. According to Shimano press officer Devin Walton, “We’ve always got products and prototypes that we’re working on, developing, and preparing for sale once the concepts and products have been proven. I think the prototypes that have been 'spied' at various pro events are a prime example of that development process in motion.”
Official or not, it’s common knowledge that Shimano will eventually unveil two new Dura-Ace groups for 2009. We’re still on the hunt for good close-up images, but the information is compelling enough on its own for now.
The new 7900 group will use traditional mechanical connections for its gear-shifting and replaces the current 7800 Dura-Ace. The other - Dura-Ace Di2 -
will use the electronic system Shimano has been testing.
Dura-Ace 7900 mechanical: faster and lighter, but broader appeal, too
Dura-Ace 7900 looks to be a significant step forward in performance but Shimano has also tried to increase the group’s usability for more casual riders. The mechanical version will reportedly be over 180g lighter than Dura-Ace 7800. Along with that weight loss comes improved drivetrain efficiency; faster and more robust shift performance; and a wider range of gear options than before.
More cable, please
Shift quality has always been a Shimano priority and the new 7900 group will have increased cable pull. This means that the new drivetrain should be far more tolerant of housing contamination, slight maladjustments and hanger dimension variances. However, the new shifters and rear derailleur won’t be compatible with any other 10-speed Shimano.
Even with the increased cable pull, shift lever throw is reportedly 20 percent shorter than before. Currently there’s no word on whether Shimano will include the Multi Release or Instant Release features from XTR M970 for even faster upshifts. We’d be surprised if neither showed up.
The new STI Dual Control levers will have a flatter and more hand-friendly hood shape. Carbon brake lever blades and titanium hardware will drop some weight. Adjustable lever reach will better accommodate smaller hands and a wider assortment of bar bends. The derailleur cable housing will be concealed beneath the bar tape for a cleaner appearance.
Optional equipment for the new levers includes an updated Flight Deck integrated wireless computer. In addition to the usual speed and distance functions, the new Flight Deck will add an on-board altimeter, inclinometer and heart rate monitor. For the first time, ride data will also be downloadable to a PC for later analysis.
The rear derailleur lightens up with a carbon cage while capacity on the standard cage has been increased to 28 teeth (that suggests the mid-length GS version has been deleted). The front derailleur has been retuned for even lighter shift effort and the cage profile has been designed so there is supposedly no trimming required in any gear combination. While this last feature sounds decidedly untraditional, that’s also what we all said years ago with mountain bike drivetrains. If anyone can figure this out (and unleash it upon the masses), it’s Shimano.
Drivetrain: stiffer and smoother
The new crankset will still be made of hollow-forged aluminium but stiffness is reportedly increased 20 percent. A new outer chainring design bumps rigidity up 20 percent as well. It’s not clear whether or not those two increases are additive or inclusive. For the first time in Dura-Ace history, Shimano will offer a compact version. No word yet on whether there will also be a triple-chainring version.
The new Dura-Ace 7900 chain will use a 'quick connect' link for easier maintenance as well as hollow pins and milled-out side plates for lighter weight. The new chain will also be asymmetrical for reduced chain suck and increased precision will supposedly make for a 0.6 percent increase in efficiency. We’re about as excited about the 0.6 percent as you are (ahem) but that improved efficiency does suggest a quieter running chain.
Cassette weights have dropped a bit courtesy of a new aluminium carrier. More importantly, cog ratio options have broadened to include combinations that are more useful to casual riders such as an 11-28.
We don’t have confirmation on the future of the 2008 carbon fiber crankset. Given its minimal advantage over the alloy 7900 version we’d be surprised to see it carry on another season. We have heard, however, that a BB30-compatible alloy version may be on the way though that’s strictly an unsubstantiated rumour at this point.
Refined dual-pivot architecture is alleged to improve power and modulation over current offerings and cable routing has been cleaned up a bit for reduced friction. A new pad compound is reported to decrease stopping distances substantially in both wet and dry conditions. Titanium hardware sheds a few grams.
Dura-Ace Di2 – shifting at the speed of light
Electronic shifting might seem to be more complicated just for the sake of being, but the technology does offer performance advantages practically unattainable with mechanical systems. Our experience with earlier prototypes indicates shift button throws are remarkably short and derailleur movements are much faster than spring-loaded versions.
The Dura-Ace Di2 group will not only shift faster than the current Dura-Ace group but our information suggests that it’s also over 100g lighter, even with the battery pack. We’ll see how close to reality those figures are come production. Some of the weight savings comes from the use of alternative materials, as on the mechanical version, but we suspect the bulk of the loss comes from the omission of mechanical hardware.
Neat features include optional remote shift buttons for time trial setups; a ‘crash position’ that helps shield the rear derailleur from damage during a fall; and an auto-trimming front derailleur. We’re not sure why the latter is necessary if Shimano is touting a ‘trim-free’ front derailleur on the mechanical version.
Reliability is always the big concern with electronic shifting. Mavic's two attempts at the idea, Mektronic and Zap, suffered from disastrous reliability and that colours everyone's attitude to electronic gear controls. However, it does look like Shimano has done its homework with D12. We’ve been seeing these components in the field for several years now and it seems highly unlikely that Shimano would release this sort of technology without thoroughly working out the bugs. Reliability is also likely to be Shimano’s primary reason for using a wired set-up instead of a wireless one.
But why bother with electronic at all, you ask? We posed the question to Walton a while back regarding electronic groups in general and it isn’t difficult to transfer his response to a performance-oriented system.
“The idea of operating a drivetrain electronically and using electrical actuation is one that Shimano has been engaged in for many years,” he said. “Take for example our Nexus Auto-D internal four-speed system. The idea was to create a drivetrain that had the least amount of potential issues necessitating adjustment and versatile, yet simple operation.
“Friction and cable contamination are removed by using electrical signals; precision is ensured by precise servo motor movement; adjustment and accuracy are monitored with each shift; the user interface can be operated via a simple push of a button or using an automatic mode.”
An automatic mode? Um, okay. Battery life is expected to be in the range of months for typical users although there’s no word yet on what happens if it dies out on the road.
“It will make everyone else’s road groups look like toys”
That was the comment we heard from one industry insider (who doesn’t work at Shimano) and it’ll be interesting to see if that holds true. We’ll reserve judgment until we have access to a proper test session on production gear but one thing is certain: the market is heating up yet again and we all stand to gain.
Thursday, April 03, 2008
By Ward W. Brien
When we zero in our rifle at 100 yards, we are shooting on a flat plane with the full force of gravity pushing down on the bullet. In order to zero properly and get the bullet to strike the bulls-eye, we need to adjust the sight height above the bore of the barrel for this particular condition, (shooting on a flat plane) so that when the bullet leaves the bore of the barrel it arcs up into the full force of gravity, and then drops down onto the bulls-eye.
However, when we shoot on an incline or decline (up or down on an angle) the force and effect of gravity is less on the bullet; but the sight height above the bore of the barrel remains the same, or adjusted for shooting on a flat plane.
Because of this, the bullet will have a flatter trajectory and strike the target higher than where our intended point of aim was. It is imperative that when we are shooting up or down on an angle that we eliminate the guesswork, and correct the straight line distance to the target or “sloped distance,” to the, corrected for gravity, distance to target.
Now, this is an easy adjustment; a simple equation that will put you very close to right on target. However there are three ways to obtain this and one is more accurate than the other.
The first method is called the field expedient “Rifleman” method. As an example, when a surveyor is shooting a mountain top for mapping purposes, he uses an instrument called a theodolite. The theodolite tells the surveyor the angle of his aim. His/her goal is to obtain the base of the triangle distance, or flat line distance. Hence, simple geometry comes into play. The surveyor notes the angle that he is holding at, then goes to his data book and obtains a cosine number of that angle, which he then multiplies to the sloped distance.
Below, referencing a .300 Remington Ultra Mag, utilizing a flat shooting 180 grain Nosler Partition bullet, with a velocity of 3250 feet per second, the uncorrected for gravity distance of 500 yards to target would cause the bullet’s point of impact (under the field expedient method) to hit approximately 13.2 inches high; or 1.75 minute of angle. Please see the Night Force ballistic Targeting Software Generated Angle Drop chart below.
To the average hunter, these trajectories, at first, may not appear to be significant, but as an experienced shooter you know that they are; and the angle that you will be holding on demands a correction. As an example, let’s say that your rifle shoots an average group size of one inch at 100 yards (large for a pro-grade rifle). At three hundred yards the group size could hypothetically open to three inches; at five hundred yards, five inches. So, if you are going to be thirteen inches high at 500 yards if uncorrected for gravity, then you can add an additional five inches to that, in any direction. This is not difficult to see; math is math and science is science and when the math is done correctly, one round will put one animal down.
Figure 3 – Angle Drop Table for the 300 Rem Ultra Mag
The U.S. Military as well as other Government agencies, train all of their Precision Marksmen on how to obtain the corrected for gravity distance to target. The original method of approach was to utilize a Protractor, string and paper-clip. The string was tied to the center of the protractor and weighted with the paper-clip. When the Marksman was aiming at his target, the protractor was held in place with the weighted string along the side of the receiver inline with the barrel. The Marksmen would then carefully grab the protractor and string, and obtain the angle that he was holding on. Then, the Marksman would go to his data book and obtain the cosine number, then do the math; very simple and very straight forward. Only today there is an easier, faster and more dependable method of obtaining the cosine number; and that is by using an “Angle Cosine Indicator” manufactured by “Sniper Tools Design Company.”
To install the Angle Cosine Indicator you will first need to decide on your method of mounting; either a Weaver base scope ring or a Badger Ordnance’s Picantinny rail mount. Once that is decided, you will level the bore of your barrel by placing a spirit bubble level on the inside rail of your receiver, which is where your bolt lugs ride on. Once the bore is level, install and zero the ACI, insuring that it is indeed level with the bore of the barrel and the zero cosine number is sitting ontop of the index mark. Once that is accomplished, you are ready to hunt. The following is the procedure for utilizing the ACI while in the field.
1) You spot your target. 2) Range / obtain the distance to your target by either utilizing a laser range finder or a ranging reticle. 3) Aim at your target and then look off to the side of your rifle at the Angle Cosine Indicator and obtain the indicated Cosine number. 4) Multiply the cosine number to the distance to your target, which will give you a corrected for gravity distance.
For example, 500 yards X .7 (45 degrees) = 350 yards. Now, look at your data card to obtain your hold for the 350 yard target distance, and adjust your turrets as specified. However, this is the least accurate method of the three.
2) In the second method of obtaining the corrected for gravity distance to target, the ACI still plays its role, however the cosine number is multiplied to the hold data from your “data card.” When I instruct angle shooting to my Students, I teach how to utilize Night Force Ballistic Targeting Software which is loaded onto a Pocket PC, to manufacture a data card. The procedure is as follows:
1. Utilizing a Kestrel hand held weather station, obtain the temperature, barometric pressure and humidity.
2. Input this data into the data entry points of the software.
3. Pick the “Drop Table” button.
There is a little bit more to this than what I have mentioned, however this procedure produces an electronic data card with distances in one, five, ten, twenty, twenty-five and fifty yard or meter increments; your choice. I then have the Students copy this data card over to small “write in the rain” notebook paper. Then, place the Pocket PC back into their pack and either tape the card to their stock or place it in their jersey pocket. While in the field and after obtaining the distance to target, the data card is reviewed, and the cosine number is multiplied directly to the hold, as depicted on the data card. This method is more accurate than the “Rifleman” method and is called the “Improved Rifleman” method. Looking above at Figure 3, if the target is at 500 yards, the hold for that distance is 7 moa. If you were aiming at a 45 degree angle, the cosine would be .7 and the calculation would be as follows: .7 X 7moa = 4.9 moa.
However the most accurate method is to input your meteorological data, (temperature, barometric pressure and humidity) directly into the “Night Force” ballistic targeting software. This is because the software takes into account the fact that the bullet has its own unique velocity, ballistic coefficient, time of flight, and deceleration curve. Utilizing this software can be as much as eight minute of angle more accurate then the Rifleman method and eliminates the guessing game once associated with angle shooting.
Ward Brien is a US Army Veteran, Owner of Sniper Tools Design Co., LLC and the Inventor of the "Angle Co-Sine Indicator," which is sold and under contract to different branches of the US Military, British Military and others.
Located in the top of the Colorado Rockies, Ward also instructs a specialized three day Precision Shooting 1 course to Hunters and Tactical Precision Shooting to the Military and other Government Agencies.