The Ultimate Guide to the Capabilities and Versatility of an ABC Watch

On any given day, I carry an assortment of tools and devices to help me complete my mission or pursue my outdoor activities. One such tool that I carry is my Casio Pathfinder PAG-240 watch. The Pathfinder is an ABC watch, and I have been a faithful user of the Pathfinder for about 9 years. I come from the camp, that if you do things outdoors, you should wear some type of timepiece.

Casio Pathfinder PAG-240.

What is an ABC watch? 

An ABC watch is a rugged multi-sport watch, which utilizes sensors to determine elevation, atmospheric pressure, and direction. ABC is short for altimeter, barometer, compass. ABC watches also have functions found on traditional sports watches such as alarms, stopwatches, and timers.

There are probably two different types of users in the world of multi-sport watches. Which are the ABC watch or the GPS watch user. There is an ongoing debate about which watch is better. Just like which is better, using a smartphone or a dedicated GPS for navigation. No matter which camp you are in, both have their merits and shortcomings. In this post, I am only going to focus on the ABC watch, and in particular the Casio Pathfinder PAG-240. 

How accurate are they?

You have to keep in mind that an ABC watch is not a precise instrument and should trust the information as an estimate. If the watch is properly calibrated, it can be a fairly accurate device. An ABC watch should be complementary to other tools that you use, not a substitute. I will cover accuracy in more detail later in the post and how we work with its limitations. So, just stick with me until we get there.

Why do I wear an ABC Watch? 

Because of my military profession and my active lifestyle, I prefer a watch that does a little more than tell time. I don’t need a watch that knows more about me than I do. I require a timepiece that can be used for a multitude of functions no matter what I am doing. There are times when I either cannot access my smartphone, or I cannot have it with me. This is where the ABC watch comes in handy and that it provides the required information that I am looking for. Below are the basic requirements that I look for an ABC watch. 

  • Accurate timekeeping 
  • Long battery life
  • Stopwatch 
  • Sunrise/Sunset 
  • Non-tracking or social engagement
  • Altimeter
  • Barometer
  • Compass 

When I started researching for this post, I was surprised by the lack of information on how to set up and use an ABC watch. Most of the posts on the subject were about what watches were the best to buy. On the watch forums, the ever-going debate of which ABC watch vs GPS watch is better or can even compare the two. 

I found none of this helps me understand the capabilities and versatility of these devices. The lack of quality information has required me to dig a little deeper to understand their limitations and if calibrated appropriately, will allow us to utilize, in this case, the PAG-240 to its potential. I cannot stress enough how important planning is to achieve the best results with the altimeter and barometer functions. There are four resources that I find helpful in the planning process. These resources will be covered in more detail throughout the post.

In this post, I intend to cover the known limitations of an ABC watch, and in this case the Casio Pathfinder PAG-240. I am going to describe how I calibrate the watch to maximize the watch's potential. Lastly, the different features I use and provide examples of how I use those features in my military profession and how I use those same features in my outdoor activities. 

The Casio Pathfinder PAG-240 has a plethora of features that enable the user to accomplish a multitude of tasks. In my opinion, any of the Casio Protrek or Pathfinder models are a practical choice in an ABC watch purchase. Remember there are limitations, and the watch should be complementary to other tools that you use, not a substitute. 

  • Timekeeping 
  • 12/24 hour format 
  • 31 time zones (48 cities codes) 
  • Stopwatch 
  • Countdown timer 
  • Sunrise/Sunset 
  • Calendar 
  • Alarms (five daily alarms) and hourly time signal 

Altimeter

The altimeter can measure altitude by a barometric pressure sensor or reference altitude specified by the user. Altitude is displayed in 20ft or 5-meter increments. 

Barometer/Thermometer 

The barometer pressure can be set to display in inches of mercury 30.20 (inHg) or hectopascals 1023 (hPa) The thermometer can be set to display a temperature value in Celsius (°C) or Fahrenheit (°F). 

Compass 

The bearing sensor detects magnetic north and indicates 16 cardinal directions. The user may also set magnetic declination correction (the difference between magnetic north and true north). 

Casio is one of the few watch manufacturers that produces solar-powered watches. The Pathfinder PAG-240 comes with an integrated solar cell that can power the watch indefinitely. That doesn’t mean that the CTL1616 battery will never go bad and need to be replaced. I have replaced the battery in my PAG-240 once in 9 years. 

Timekeeping Mode 

I prefer my watch to display 24 hour time. Referred to as military time in the United States and 24 hour time elsewhere in the world. Since I have to use the 24-hour format for work, I am accustomed to that format. The benefit of using 24 hour time takes the confusion away from A.M. (morning time) and P.M. (evening hours). 

If you choose to display 12 hour time, there will be a “P” to the left of the time to let you know that the time is P.M. (evening time). 

Pro-Tip 

Resources for Time: 

Selecting one of the 48 city codes nearest to where you live, will assist you in setting your local time. For example, if living on the east coast of the United States let's say in Harpers Ferry West Virginia, you would need to select New York (NYC) as your city code. Using the websites above will help you set the most accurate time to your location. 

The Official U.S. Time website

 

The Pathfinder also has a World Time Mode (WT), and after you have set the city code the watch will use UTC offset to calculate the current time for other time zones. Since we use Daylight Savings Time (DST) in the United States, DST can be selected. Doing so will cause World Time to be off by an hour. 

Coordinated Universal Time

The Pathfinder keeps excellent time and the only time that I make adjustments is when I have to set the time for DST. In six months, the watch might be off 20-30 seconds. 

Pro-Tip 

If for some reason you need to update your time or get a group of people to sync their watches and do not have access to the resources for the time listed above. Use a dedicated GPS to set the time. This enables users to determine the time to 100 billionths of a second. 

Why is time important? 

For the military, it cuts down on the confusion between A.M and P.M. hours. The military doesn’t have a 9:00 at night. We would say 2200 hours. The military also uses Zulu time which is the same thing as UTC and PAG-240 displays it as World Time. Zulu time is an aviation standard and avoids confusion flying between time zones. 

The accuracy of time is important and lets us figure out calculations of how long an aircraft can fly against the rate of fuel that is being used. Speed, distance, and time allow crews to navigate. If I tell you that the aircraft is going to pick you up from your mission five minutes after midnight. You can trust me that the aircraft will be there +/- 30 seconds to get you out of there.

For backcountry travel and navigation, If you know your speed then the use of time is a better technique to use than pace count over a long distance. A stopwatch is a great tool for this task. 

I know it seems like a lot just to set the time. But making sure that we have set the watch time up accurately will help us set up other modes properly. 

Sunrise/Sunset Mode 

After timekeeping, the next mode that can be selected is Sunrise/Sunset. Many variables affect sunrise/sunset times on ABC watches. They include environmental factors such as latitude, longitude, and altitude. Your physical relationship within a given time zone. There are also design limitations. In this case, the Casio Pathfinder PAG-240 displays sunrise/sunset in 5-minute increments and those times are based at sea level. The good news is that we know these limitations and can correct some settings that will provide a more accurate time. 

There are three different types of twilight: 

  •  Civil twilight 
  • Nautical Twilight 
  • Astronomical twilight 

The use of Light Data for tactical planning and military operations is important and sunrise/sunset is just one component of what Light Data provides. The following terms are used. 

  • Beginning of civil twilight (BMCT)
  • Ending of civil twilight (EECT) 
  • Beginning of nautical twilight (BMNT) 
  • Ending of nautical twilight (EENT) 

So, what do these twilights mean? 

In civil twilight, there is enough natural light that artificial light is not needed. Such as headlamps, and street lights. The military terms Beginning of Civil Twilight BMCT and Ending of Civil Twilight EECT are the military terms for civil dawn and civil dusk respectively. 

In nautical twilight, there is only enough light to see the general outlines of ground objects but you still cannot conduct outdoor activities. The military terms Beginning of Nautical Twilight BMNT and Ending of Nautical Twilight EENT are the military terms for nautical dawn and nautical dusk respectively. When I was in the infantry, this was the time of the morning which we would start pulling "stand to". It would still be dark, and we would either pull security at 50 or 100 percent until it was daylight. I am sure we did the same thing in the evening but I don't remember it as much as I did in the morning. That was the hour of hate! 

Astronomical twilight is when the sky becomes completely dark and any celestial bodies can be viewed by the naked eye. 

Pro-Tip 

Resources for Sunrise/Sunset 

NOAA Solar Calculator website

 

Calculating adjustments 

Keep this in mind, one degree of latitude is approximately 69 miles and one degree of longitude is approximately 54.6 miles. The sun’s light moves across the earth at a rate of 15 degrees longitude per hour. While this is not exact you can figure for every 70 miles west you travel within your time zone, sunrise will be about 4 minutes later. Also, altitude plays a role in this too. For every mile in altitude, the sunrise will be one minute earlier and the sun will set by the same amount. 

Sunrise/Sunset Mode

 Pro-tip 

Looking at my watch I can tell that the sunrise and sunset times are way off for my location. To fix this issue we are going to drill down a menu and add the latitude and longitude of my location. Because the watch will only allow me to add degrees the accuracy is still going to be off a bit. 

Why is sunrise/sunset important? 

For Skiers, Climbers, and Mountaineers the sun is the primary factor affecting the conditions and quality of the snow surface. The amount of daylight lets climbers plan if they can make their ascent or will have to plan for a bivouac. Photographers use sunrise/sunset to be on location to capture an amazing landscape, and wildlife photos using the best natural light called the “Golden Hour”.

Military plans and operations use sunrise/sunset times to increase security or know which type of assets to use due to the amount of ambient light. 

While the Casio Pathfinder PAG-240 will let you search what the sunrise/sunset times are on different days of the year. Other models of ABC watches may also provide moon phases. For most people’s needs, this information is all they will ever need.

For military or other special applications, this might come up short. The need for other light data such as moon phases, moonrise, moonset, lumination percentage would be best provided in a battlefield weather forecast. 

Photographers and amateur astronomers benefit from the same data that is used in military applications.

Altimeter, Barometer, and Compass modes 

It is safe to say that the altimeter, barometer, and compass on an ABC watch are not as precise an instrument as a dedicated altimeter, barometer, or compass. Some limitations and precautions need to be covered along with some terms that are confusing when communicating with others.

Aren't Azimuth, bearing, and heading just different ways to say the same thing?  

These terms are often used interchangeably but there is a difference and it's important to know what the terms are when you have to communicate directly with someone. 

  • Azimuth is a measurement as it pertains to a compass. An Azimuth can be read in mils (6400) or degrees (360°). 
  • Bearing is a direction of measurement as it relates to north/south and east/west. Example N45E 
  • A heading in the direction you are facing. In many cases, the way you are facing is the same as your azimuth. 

How many northerly directions are there? 

There are three different types of northerly directions. 

  1. True North 
  2. Magnetic North 
  3. Grid North 

The Casio Pathfinder PAG -240 has a built-in magnetic bearing sensor which means that the compass mode indicates magnetic north. 

Precautions 

  • Some maps indicate true north instead of magnetic north. Adding declination correction allows the digital compass on the watch to indicate true north. Declination correction on the PAG-240 can only be added as a whole number. 
  • The Pathfinder is affected by metal just like a compass. Avoid taking directional readings near metal objects, high tension wires, vehicles, and weapons. 
  • As stated by Casio, the Pathfinder PAG-240 compass has an accuracy of +/- 11°. The auto light switch is temporarily disabled while the digital compass reading takes place. 

Digital Compass mode 

The compass mode is by far the hardest feature to master on the Casio Pathfinder PAG-240. There are some inherent accuracy issues with the compass, and I will provide some pro-tips that will help minimize those accuracy issues. But if you find yourself in terrain or other situations where losing your way will be dangerous, have a primary compass to confirm direction. 

Accuracy and limitation issues 

The compass accuracy stated by Casio is +/- 11°, which is not acceptable for precision navigation over distance. While wearing the watch and taking a reading the slightest movement of the wrist will compound the issue. Traditional liquid-filled compasses have a superior settling of the compass needle over the north pointer on the PAG-240 which seems impossible to achieve. 

What does the accuracy of +/-11° mean on the ground?  

Taking a compass reading of 90°, the accuracy of your azimuth could be anywhere from 79° to 101°. One degree in error over 100 ft. or 30.4 meters puts you 5.2 ft. or 1.5 meters off course. With that error, finding your point is still doable. But that same reading at an 11° error you would be off the course by 57.2 ft. or 17.4 meters. That amount of error is still manageable. Finding a feature 1000 ft. away could be near impossible. I conducted a field test to see if the math held up, or would I have better results. See the results of my field test below. 

Calibrating the Bearing Sensor 

There are three different calibration methods, and they should be used when you feel the azimuth reading is off or your method of navigation you are using. 

  •  Magnetic Declination Correction
  •  Bidirectional Calibration 
  •  Northerly Calibration 

The magnetic declination correction allows you to manually input the difference between magnetic north and true north. Maps can either be true north, or magnetic north. If the map sheet is magnetic north, the map will display the declination diagram which will provide the declination angle. On the PAG-240 input of the declination correction can only be added as hold numbers. 

Declination Diagram image from the USGS

 

In the graphic above the declination correction, 13.55° would be rounded up to 14°. 

Bidirectional calibration and northerly calibration are two different calibrations, and it seems to be the most confusing. Whenever you have changed environments or believe the compass has been magnetized, you should make a bidirectional calibration. This is best done by using two opposing directions from one another. To perform this procedure correctly the opposing directions have to be 180° from one another. Follow the calibration procedures in the owner’s manual. Failure to do this correctly will give you an inaccurate sensor reading. 

With that said, the bidirectional calibration will zero out the northerly calibration settings. Which in turn, you would need to do both calibrations. To do the northerly calibration correctly, you will need to have a compass to perform this calibration. Place the compass on a flat surface. Place the watch on a flat surface and turn the watch, so the 12 o'clock position is facing the same direction as the north needle of the compass. Follow the calibration procedures in the owner’s manual. 

No matter which brand of ABC watch you own, I highly recommend that you closely follow the steps in the owner’s manual to properly perform the calibration procedures. 

Direction of Travel 

Unlike traditional baseplate compasses, ABC watches do not have a direction of travel arrow. Instead, the 12 o’clock position is used as the direction of travel. 

Field Test 

I conducted a field test to see how accurate the compass is on my PAG-240. Utilizing the bearing line tool in caltopo.com, I drew a bearing line from a bridge on a forest road, which would be my starting point. Following an azimuth of 318°, my endpoint would be an old homesite approximately 1200 ft away. Since my compass was noticeably off, I performed a bidirectional and northerly calibration. 

Pro-tip #1 

On the inside of the bezel ring, hash marks indicate every 10° and numeral degree markings for every 30°. Knowing the azimuth that you are to travel, turn the bezel ring so the azimuth is at the 12 o'clock position. Rotate yourself until the north pointer is lined up with the "N" on the bezel. You should now be facing the azimuth that you want to travel. This method should aid in taking quicker azimuth readings to verify that you are on course. 

Pro-tip #2 

Holding the watch like a traditional compass or using a bracing method to hold the compass is a better technique than using the wrist method. This allows the compass needle to settle, providing better azimuth accuracy. 

Bracing method

 

In this test, I did not utilize a map to aid with terrain association. Instead, I just used dead reckoning to get a better assessment of the compass. When I arrived at the old home site I was 10-12 ft to the right of the old foundation. Based on my results I would estimate my compass degree of error is between 2-5°. I was very surprised at the results.

The old homesite used during the field test
 

Pro-tip 

During nighttime or limited light operations, some type of light is required to be able to operate and see the compass display. This is because the auto light switch is temporarily disabled while digital compass reading takes place. Flashlights, headlamps, and chem lights with red or green light capabilities are the best to use and aid in preserving your night vision. 

**Note, turning the light switch on after the compass reading, I have noticed that my compass mode will stop functioning.** 

Final thoughts on the compass mode. 

The digital compass mode is the most difficult mode to calibrate and master. While the results of my field test were successful. The user needs to be a very proficient navigator to compensate for the accuracy and limitation issues of the digital compass feature. The compass mode should not be used as a primary compass but for general headings and backup use. For users that still require a secondary wrist compass, then something like a Suunto M9 would be a better choice. 

For the recreational user, the digital compass would aid in activities such as urban hiking, landscape photography, and astronomy. For military users, the digital compass provides quick reference access for the user. Provides general direction to help establish such tasks as communications, secondary navigation, and escape & evade. 

Barometer/Temperature Mode 

No matter where your adventure takes you, the weather will affect your activities. ABC watches are built with barometer and temperature sensors. The barometer measures changes in pressure. This enables the user to apply the reading to their weather predictions. 

Over my military career, I have received training on how to interpret weather reports and forecasts to determine how the weather conditions are going to affect my mission. I take that same training to determine how the weather will affect my outdoor activities. 

Unless you are an amateur meteorologist you are not going to be able to predict the weather with the barometer and temperature sensor on an ABC watch. Meteorologists use various scientific instruments to be able to predict and forecast weather. What these sensors provide is situational awareness that a change to the current conditions will take place.

Precautions 

  • Sudden temperature changes can affect pressure sensor readings 
  • Wearing the watch, direct sunlight, and moisture affect temperature readings 
  • The barometer is not a precision instrument and should not be used for any formal weather predictions or forecasts. 

Temperature Mode 

The temperature sensor is affected by body temperature, direct sunlight, and moisture. To measure an accurate temperature reading, remove the watch from your wrist. It takes approximately 30 minutes for the watch to measure an accurate ambient temperature. The temperature on the PAG-240 can be set to display in °C or °F and the temperature range is from -10.0°C to 60.0°C or 14.0°F to 140.0°F. 

Field Test 

I conducted a non-scientific test to see how accurate my Casio Pathfinder PAG-240 temperature reading is. Having been outside in the cold I conducted my test indoors. I took the watch off and set it down on a flat surface. I monitored the temperature reading against the wall thermostat. In about 30 minutes the temperature sensor stopped adjusting to the inside temperature. Accuracy was within 2 degrees of the thermostat temperature reading. 

Pro-Tip 

Resources for Current Barometer Readings 

Barometer Mode 

The barometer sensor is used to detect a change in pressure. This will normally allow the user to assess current weather and take necessary actions over the next 12-24 hours. The barometer also plays a role with the altimeter which I will discuss later in the post. 

The barometer can display in units of 1hPa or 0.05 inHg. I prefer to set my barometer to inHg because of the military and civilian resources that I use the display in that format. The barometer displays hold numbers only. Example 29.70 inHg, 29.75 inHg. 

Barometric Mode

 

Barometric Pressure Graph 

The term short-term weather forecast means different things to different people. But I determine a short-term forecast to be about 48 hours. Anything past 48 hours I do not find dependable. In remote locations and longer trips, it might be impossible to get updated weather forecasts. 

This is where the barometric pressure graph comes in to bridge that gap. The barometric pressure graph is the easiest way to understand and visualize the changes in atmospheric pressure. 

Interpreting the graph 

The graph displays both time and barometric pressure. Horizontal each square block or dot represents two hours. Vertical each square block or dot represents pressure. A rising graphic display generally means improving or favorable weather. A falling graphic display generally means deteriorating or unfavorable weather conditions. The graph displays the barometer readings for up to 24 hours. If the display skips a reading this is due to two reasons: a sensor malfunction or the reading is out of gauge range. 

Pro-tip 

The barometric pressure graph can be displayed in the timekeeping mode display format. This provides quick access to interpreting weather conditions while in the timekeeping mode. 

Altimeter Mode

 

Altimeter Mode 

Most users of ABC watches might not need the altimeter for any more than knowing how high was that viewpoint that they hiked today. Or for their social media post to show their friends. 

But if you are conducting intermediate or advanced backcountry travel an altimeter should be part of your navigation toolbox. The altimeter should be used in conjunction with a topographic map to help determine elevation during activities such as mountaineering, skiing, and backcountry travel in difficult terrain. 

ABC watches display altitude based on pressure readings from the barometer pressure sensor. Altitude is based on either preset values or altitudes set by the user. Altitude can be displayed; either in meters or feet. Barometric altimeters need constant recalibrating to be accurate. 

Pro-tip 

Resources for Reference Altitude Value 

Precautions 

The following conditions will prevent an ABC watch from providing accurate readings. 

  • Air pressure due to weather changes 
  • Drastic temperature changes (warm, cold & humid air) 
  • Strong impacts on the watch 

To obtain the most accurate elevation reading requires a little bit of preparation and understanding of how the barometer sensor affects errors in the altimeter accuracy. 

Above I have provided some resources that will help with determining reference altitude values along a given route. An example is knowing the reference altitude for the start point at the trailhead and other reference altitudes at other identifiable trail features such as trail junctions, campsites, or false summits.

Map used for determining reference altitude values

 

Remember that the barometer sensor only displays in hold numbers. Because the tenth number is the whole number position, the reading will be10 ft or about 3 meters off. For example, If the true barometer reading is 29.92 the watch will display 29.90 and that is going to put the accuracy of the altimeter off by 20 ft or 6 meters. 

Pro-tip 

While this tip requires some planning, I prefer to select user-selected reference altitude along with using the altitude differential value. You can select reference altitude from a map or better yet use Google Earth to get the altitude of locations along your route. The altitude differential will zero out when you enter the reference altitude. The altitude differential value constantly changes value every time the sensor takes a reading. Either adding or subtracting the differential number to the user-selected reference altitude will provide you the current altitude for your location. 

There are a few other features in the altimeter mode that are available and should be mentioned, such as manual and auto measurement records of minimum, maximum, vertical ascent, and descent. 

For military applications, altimeter mode can be used to determine the altitude of a landing/pickup zone (LZ/PZ), land navigation in rugged mountain regions. I have only used the altimeter mode to find the altitude for LZ/PZ locations. 

For backcountry travel, the altimeter mode comes in handy if there is a known false summit and for navigation along rugged mountain routes where navigation could be difficult without the aid of an altimeter. 

Wrapping things up. 

If you are a current ABC watch user I hope this guide has provided the necessary information for you to better understand the built-in limitations and the environmental factors that affect the timepiece you have. How to properly calibrate your timepiece can greatly enhance the user experience and can be a fairly useful tool no matter your pursuit. This ultimate ABC watch guide was based on the Casio Pathfinder PAG-240.

Just remember an ABC watch should be complementary to other tools that you use, not a substitute. Possess the necessary skills and knowledge to utilize the tools at your disposal. A good understanding of weather and navigation is a plus when using the watch for those tasks. The following resources are not the only ones out there NOAA Jetstream and Orienteering Training but they can help in that effort. Seek out the training you need to be more proficient. 

 Now It's Your Turn-

Do you use an ABC watch or a GPS watch? What features and modes do you use? How have you used your ABC watch in the field?

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