Google is good, but not good enough. Maybe someone here can help resolved this.


I am trying to figure out if it is possible to determine my location when I take a bearing of two mountain tops that are not on the map, if I have pre-drawn a line to the center of the map from each mountain (see attached).

I have access to digital 1:20,000 maps and I create my own maps to cover only the area I am going to be hiking in. No reason to carry a 1:50,000 when I am only going to cover 40km in a weekend. 1:20 gives greater detail and most places I go require two maps because the area overlaps from map to map.

I have attached a visual of this problem. Two mountains are located outside of the map that I have in the field. A pre-drawn line from each mountain to the center of the map is marked.

With this info, is it possible to take a bearing and do some calculation to figure out my location

Would I need to put additional info on the map, maybe another bearing to each mountain from another location on the map?

Bearing + distance along the bearing.

Bearing to what? and distance to what? Could you explain with a little more detail.

If I am trying to triangulate, I only know the bearing to the mountains, I would not know any distance. Once I have triangulated, then I would be able to calculate distances.

I don't think it's possible if you only have "A pre-drawn line from each mountain to the center of the map is marked."

If you took this approach instead:
At each corner of the map, write two numbers that represent the bearing from that location (the corner of the map) to each of the two mountains.

..then you could make it work. You would need some straight edges and a bit of patience.

To be more precise: You need to know the angles from two locations on the map to each of the two mountains. That's four angles total as opposed to the two that you drew on your sample map.

It would be hard to do this in the field though since it requires you extrapolate beyond your map with some straight edges.

As an alternative method, you could make a tick mark (one for each 5 degrees in angle change) along the edge of the map. Once you get your bearing to the first mountain, you could draw a line at that angle through the appropriate tick mark. Once you get your other bearing, you would do the same for the other mountain and where they intersect is your location.

Too complicated. A key premise behind map and compass work is simplicity - why introduce variables that will only help get you lost.

Besides, I don't think your method works.

I don't think Steventy's method works either - when out in the field, you can't determine where the corners of your map are unless you a) know exactly where you are, and b) can precisely determine the distance from you and and that corner - and it's also very complicated

not having much map skills, that seems hard to me. I would just bring 3 pages of map that could be lined up with the mountains. then you're still getting the hiking area blown up to 1 sheet.

otherwise you could draw say 4 lines from each mountain across the map equally spread out. and write the bearings on them measured from the map. (ie 180, 150, 130, 100 or something) basicly creating a grid layout. when you were out and took bearings, you could place yourself inside one of those grids, and probably guess pretty close where inside the grid as well. not going to get exact location, but probably close.

You don't need to know where the corners of the map are for my proposed method to work.

Basically the procedure is as follows:
- Place your map on a flat piece of ground and treat the ground like a big piece of paper.
- Draw lines out on the ground from the corners to locate where the mountain would be located if the paper was big enough (you need an angle from at least two corners so you have two lines that intersect to mark the location.)
- Now take a bearing to the mountain and draw a line on the map so that it would go through the mountain (which you have temporarily located in map space by making a mark on the forest floor beyond your paper map.
- Do the same for the other mountain.
- Now travel for a while and repeat the entire thing.

It's a gross method. It requires you to be able to place the map on a reasonably flat piece of ground and draw straight lines out on the ground to effectively extend the area of the map. Paper is light and cheap and it would be much better to just bring a big enough map.


The second idea - putting tick marks on the side of the map to correspond with each bearing - is much more practical but it's still a bit gross.

Wouldn't a better way be for the OP to learn to read maps better and with finer detail is you can take points off of smaller terrain features? Cause you're not always going to be high enough to see the larger peaks anyhow.

Anyhow I'll thinking this some more and get back to you to,morrow - fun problem!





Edited to clarify who I was talking to

Actually it would work - the method of putting tick marks on the map edge, though it would require two sets for each mountain. Effectively putting two compass circles around each mountain allowing you to draw intersecting lines based on reverse bearing.

see attached

This would give you a very good idea of the area you are in, then you would be able to verify your location with the terrain features immediately around that area.


I suspect if you hike and don't know spatially where you are on the map and can not point out where you should be based on hiking with a map in hand, there are greater problems in your future that include SAR

I agree - learning to read a map and knowing how to use it is the most important - something I do very well. Now that I create my own maps - this idea/problem has come up, and has been solved.


Thanks for the solution!

so you would have to put tick marks along the both circles with pre defined degrees? and then in the bush could draw a line between the 2 ticks. simualar to my idea execpt the lines would already be there instead of just ticks, no ruler or pencil needed to locate yourself.

one problem I see is if you were in the bottom left of the map. you wouldn't be able to draw a line to B as the aligning circle would be off the page.

@smac -- yes, similar to your idea

I agree -- there would be some zones/areas that you would not be able to do this from. If you added another point of reference, that would cover that issue. Though you could end up with a map full of 'circles and ticks' instead of just bring more maps, printing a larger map or scaling to include the areas outside of the map.

I see what you're doing, and the tick mark method would work, but maps are light and I don't see why you wouldn't just print more/bigger maps.

You can just download the app for that

The problem is a fine reason....or carry another map or make your scaled map cover a larger area. You're over complicating matters and like another poster said, maps wiegh next to nothing.