Accurately using a map and compass for navigational purposes requires you to understand the differences between magnetic north, grid north, and true north. Declination is the angular difference between these points and is an important concept to understand when determining your location while outdoors. In this guide, we will explain how to adjust the declination on your compass to ensure that you have the most accurate bearings when navigating.
1. Defining Declination
What Declination Is
Declination is the angular difference between magnetic north and true north, which causes compass needles to point to a slightly different direction when compared to maps. Magnetic north can also be referred to as grid north, which is the direction that a map indicates north. Compasses are calibrated to point to magnetic north, while all maps are standardized to true north, resulting in a difference of declination. While declination value can vary depending on your location, it is a constant value in the same location.
Why It’s Important For Navigation
The declination adjustment on your compass can be used to calibrate the needle to point to the correct direction when determining bearings. Therefore, understanding declination and adjusting it on your compass accordingly is essential for determining accurate directions when navigating with a map. Without making a declination adjustment, you could travel in the wrong direction and get lost in your journey.
2. Different Types Of Compasses
Baseplate compasses are the most common type of compass and are the easiest to use. It typically includes a baseplate, housing units, and a direction of travel arrow. The declination adjustment on this type of compass is located on its housing unit (which also serves as the rotating bezel). It can be adjusted with a screw or a knob, depending on the model.
Magnetic compasses, on the other hand, usually don’t have an adjustable declination feature. This type of compass is typically used with a map and is more suitable for hiking, orienteering, and other outdoor activities. Since the declination adjustment is fixed, you have to make the necessary adjustments while reading your map. As such, you must factor in the declination value when navigating with a map and magnetic compass.
3. Adjusting The Declination
Setting The Declination On A Baseplate Compass
Adjusting the declination on a baseplate compass is necessary for ensuring that your compass needle is pointing in the right direction. To do this, you will need to adjust the housing unit or bezel on your compass. First, you need to identify the declination value in your area. Once you know this, you can then use a screwdriver or an Allen key to turn the screw (or knob) to the corresponding declination angle. Make sure to align the declination lines with the direction of the arrow before tightening the screw.
Compensating For Magnetic Declination In Your Map
If you’re using a magnetic compass, the declination adjustment cannot be made on the compass itself. Therefore, you must be aware of the declination value in the area you’re navigating and make the necessary adjustments to your map accordingly. For example, if the declination value is 8° east, then you should move your compass needle 8° in a clockwise direction when navigating with your map.
4. Tips For Navigating With A Compass
Keep The Compass Level
For an accurate reading, the compass must be held level and both ends of the needle must point together to indicate a true magnetic north. When the compass is tilted, the magnetic dip increases and can cause the needle to deflect from the exact orientation of the magnetized north. Therefore, it is important to keep your compass level when taking readings.
Keep Your Compass Away From Sources Of Interference
Compasses are sensitive, and any external sources of interference can influence the magnetic field of the needle and cause it to show incorrect readings. For example, metal objects, electrical equipment, and powerful magnets can affect the compass needle and cause it to deviate from the correct orientation. Therefore, it’s important to keep your compass away from any possible sources of interference.
Practice Reading A Map And Taking Bearings
To get the most of your compass, practice taking bearings and navigating with a map. Take time to familiarize yourself with the different features on your map, such as contour lines, water features, and route information. With more practice and experience, you’ll soon become an expert navigator and have a better understanding of how to use a compass.
5. People Also Ask
How Do You Adjust The Declination On A Compass?
The declination adjustment on a baseplate compass is located on its housing unit. You can adjust it with a screw or knob, depending on the model. For magnetic compasses, the declination adjustment cannot be made on the compass itself, so you should make the necessary adjustments while reading your map.
How Do I Know The Declination Value?
You can find the declination value for your area from a variety of sources, such as topographical maps, online sources, or by contacting your local mapping agency.
Do I Need to Make Constant Declination Adjustments?
No, the declination value for a certain area is constant, so you only need to adjust for it once. Just remember to keep your readings updated if you’re navigating in a different area.
What Should I Do If I Can’t Adjust The Declination On My Compass?
If you can’t adjust the declination on your compass, you should factor in the declination value when taking your bearings. When navigating, follow the directions of where the compass needle is pointing and not where the map indicates.
Navigating with a map and compass can be challenging at first, but with experience, you’ll soon be able to accurately identify your location and find your way. Adjusting the declination on your compass and understanding the angular difference between magnetic and true north are essential concepts for ensuring that you have the most accurate readings when navigating. With the right compass and knowledge, you’ll soon become an expert navigator and have a better understanding of how to read a map.