# Is this a valid method from taking a bearing from a map?

I want to check my understanding here. The goal is to determine your direction of travel by taking a bearing from a map using a compass, given that you know where on the map you are and where you want to go.

I'm assuming here that the compass doesn't have declination adjustment set. If this is the case, then the standard method of taking the bearing that I'm aware of is as follows:

1. Orient the map to true north
2. Draw a line from where you are to where you are going and lay compass parallel to this line
3. Rotate compass bezel until the needle overlaps the orienting arrow
4. The compass is now set to your proper direction of travel

Actually, if I understand it right, then when using this method the number on the bezel at the compass index line is not your bearing to true north, but to magnetic north - but that's okay since our goal is just to know our direction of travel.

I would like to know whether this method will work just as well:

1. Orient map to magnetic north
2. Draw a line from where you are to where you are going and lay compass parallel to this line
3. Rotate compass bezel until the needle overlaps the orienting arrow
4. Rotate bezel to adjust for declination

It seems to me that these two methods are equivalent and the only real difference is when you adjust your bearing for declination. Is this correct, or is there anything I am missing? Thanks!

You don't need to orient the map at all, this can all be worked out irrespective of where actual North is. You would generally only need to use this method if planning a route or for triangulation to determine your location. It is handy to orient the map to North for navigation and if you want to determine which peaks you are looking at, but it isn't absolutely essential if you are familiar with reading topographic maps.

Generally there are two methods of doing this. You can either take a bearing with your compass to prominent location(s) (e.g. peaks), and work out where you are on the map, then relate this to direction of travel, or you can determine direction of travel on the map first, then determine direction of travel using the below. In neither of these do you NEED to orient the map to a North.

• Draw a line on the map from where you are to where you want to go using edge of compass
• Rotate compass housing until orientation lines point North on the map
• Determine the direction of travel in degrees from North on the map, by reading off compass angle on bezel
• Relate this to magnetic North by adding/subtracting the angle of declination for your particular location. Rotate bezel for North orienting arrow appropriately.
• If you are using this for navigation, remove compass from map, now align compass North orienting arrow with needle, follow direction of travel arrow.

REI has some good basics here.

• Thank you for the comment! I have not yet tried this method for actual navigation, but when I've considered it in the past it has always seemed like the weakness would be orienting the bezel with north on the map - this seems like it would be easy to get it slightly off and introduce error. Have you found that this is the case? Or is it good enough for practical navigation despite the potential error there? Aug 7, 2021 at 14:50
• Topographic maps usually have a fairly dense grid printed on them, and compass bezels usually have several parallel lines in the bottom, so there is nearly always something that lines up nicely (though you have to pay attention to the differences between grid north, magnetic north, and true north). (Sports orienteering maps usually have lines indicating local magnetic north.) Chances are that you will introduce far larger errors when trying to follow a bearing past obstacles in the terrain! Aug 8, 2021 at 7:18
• @Ginour - good enough generally, unless there is some sort of local magnetic deviation as happens occasionally (usually volcanic rocks), though it pays to check often and actually follow the compass (i.e. have it out and look at it often when following the bearing. I've done this sort of thing over several km without being more than 100 m out at the end, even in dense forest and nothing to sight along the way. The real trick is to try to compensate equal distances when you have to go around objects (rockfall, fallen trees etc.).
– bob1
Aug 8, 2021 at 10:12