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 take 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 a camp, where 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, and compass. ABC watches also have functions found on traditional sports watches, such as alarms, stopwatches, and timers.

There are two different types of users in the world of multi-sport watches. Which is the ABC watch or the GPS watch user? There is an ongoing debate about which watch is better. 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. This post will only focus on the ABC watch, particularly the Casio Pathfinder PAG-240. 

How accurate are they?

You must remember that an ABC watch is not a precise instrument. You 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, not a substitute. I will cover accuracy later in the post and how we work with its limitations. So, stick with me until we get there.

Why do I wear an ABC Watch? 

Because of my military profession and active lifestyle, I prefer a watch that does 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 many 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 provides the information I seek. Below are the basic requirements that I look for 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 need for more 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 need help finding this. For me, to understand the capabilities and versatility of these devices. I need more quality information to dig a little deeper. Understanding their limitations, and if calibrated appropriately. This will allow us to utilize the PAG-240 to its potential in this case. I cannot stress enough how important planning is to achieve the best results. Using the altimeter and barometer functions. There are four resources that I find helpful in the planning process. I will cover the following resources in more detail throughout the post.

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

The Casio Pathfinder PAG-240 has a plethora of features. That enables the user to accomplish a multitude of tasks. In my opinion, any of the Casio Protrek or Pathfinder models is a practical choice in an ABC watch. Keep in mind there are limitations. An ABC watch should be complementary to other tools, 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 


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. 


The barometer pressure can be displayed 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). 


The bearing sensor detects magnetic north and indicates 16 cardinal directions. The user may also set magnetic declination correction. This is 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). 


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. The websites above will help you set the most accurate time for your location. 

The Official U.S. Time website


The Pathfinder also has a World Time Mode (WT). 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 for 20-30 seconds. 


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 when flying between time zones. 

The accuracy of time is important. Let 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 and navigation travel, if you know your speed. Then the use of time is a better technique 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. Those times are based on sea level. The good news is that we know these limitations and can correct some settings. This 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. 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 of Beginning of Civil Twilight BMCT and Ending of Civil Twilight EECT. These 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. These are the military terms for nautical dawn and nautical dusk respectively. When I was in the infantry, this was the time of the morning when 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. Any celestial body can be viewed by the naked eye. 


Resources for Sunrise/Sunset 

NOAA Solar Calculator website


Calculating adjustments 

Keep in mind, that one degree of latitude is approximately 69 miles. 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


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 times. To be on location to capture the 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. 

The Casio Pathfinder PAG-240 will allow you to search. The sunrise/sunset times for 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, and lumination percentages. Would be best provided in a battlefield weather forecast. 

Photographers and amateur astronomers benefit from the same data. That's 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 different ways to say the same thing?  

These terms are often used interchangeably. But there are differences between them. 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 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. This means that the compass mode indicates magnetic north. 


  • 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 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. I will provide some pro tips that will help minimize those accuracy issues. 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°. This is not acceptable for precision navigation over distance. While wearing the watch. 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. This seems impossible to achieve on PAG-240. 

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 with 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 if would I have better results. See the results of my field test below. 

Calibrating the Bearing Sensor 

There are three different calibration methods. 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 to 14°. 

Bidirectional calibration and northerly calibration are two different calibrations. These are 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. 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. 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 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 was on my PAG-240. Utilizing the bearing line tool in 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 keep 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 was used during the field test.


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, Turn 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 would compass and in activities. Such as urban hiking, landscape photography, and astronomy. For military users, the digital compass 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 barometers 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.


  • 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. It 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. 


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 the current weather. 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, I chose to display them 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. However, I determined a short-term forecast to be about 48 hours. Anything past 48 hours I do not find dependable. In remote locations and on 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. 


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

Altimeter Mode


Altimeter Mode 

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

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. This will 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. 


Resources for Reference Altitude Value 


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. Such as the start point at the trailhead or other reference altitudes. 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 be 10 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. 


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 with 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. Navigating 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 affects 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. But NOAA Jetstream and Orienteering Training 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?


Philip said…
I have same watch and I've also had it for about 9 years. I use the altimeter a lot. The fact that it's solar powered is such a great convenience. I don't know what I'll do if they ever stop making git!
Brian Wright- said…
Thanks for dropping by and leaving a comment. Like you I am not sure what I would do if they stop making the watch.

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