Using a Topo Map in the Woods

10:14 a.m. on June 27, 2008 (EDT)
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Just curious, but how does one orient him/herself with a topo map in the woods where it is difficult to see the surrounding terrain?

Several times now I have hiked/backpacked into the local state or national forests and have tried to pinpoint where I'm at on the topomap but because I could not see the surrounding terrain was at a loss to identify my location.

Other than using a GPS device, what's the best way to triangulate your location when you're in the midst of trees and can't see the surrounding terrain?


1:18 p.m. on June 27, 2008 (EDT)
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Aha! A prime candidate for orienteering! That's one of the first things you learn (after learning the basics of reading maps printed to orienteering standards). Go to the USOF website and find your local (or closest) club.

Orienting yourself using a government printed topo map is pretty difficult in limited-visibility conditions. They just don't have enough detail, and the inaccuracies are to large. However, once you learn some methods for orienteering (the sport), you can apply those.

First thing is to stay in touch with the map. Most hikers look at the map when they are already out of touch. They might look at it at the trailhead, but then put it away and don't look at it for an hour or two, maybe at a snack and water break. By then, it's too late. You have to learn "thumb navigation". When you start your trek, locate yourself on the map. Keep the map in hand the full time, following your location with your thumb. Note every trail junction, keep your eyes and head on swivel, noting all landmarks (including looking behind you frequently - things look very different when on the return or backtracking).

A second thing that helps is to use your compass to keep track of which way you are going, combined with "dead reckoning", which basically is keeping track of how far you go in a given direction. You really need to keep notes as you go or bearing and distance. How to keep track of distance? One thing is pace counting (you can use a pedometer for this). Another is knowing your typical speed and keeping track of the time you have travelled (know how much your speed varies over rocky terrain, uphill, downhill, through deadfall, as well as open meadows).

As far as the map is concerned, always orient it to the terrain (far too many people hold the map with north "up", so you can't recognize terrain features). This includes when walking along (remember? map in hand at all times, thumb following your progress). Use the compass to orient the map to match the terrain (that's really the primary use of a compass - triangulation is much over-rated (actually, what people think is triangulation is resection, the inverse of triangulation). Orienteering maps are always printed to magnetic north, where government-issued topo maps are (almost) always printed to true north (some countries use local grid north, but these are rare). So you have to know the current local magnetic declination (pilots, surveyors, and sailors use different terms for this, but this is the difference between local magnetic north and true north). A shortcut some people use is to draw magnetic N-S lines on the topo map before leaving home. By the way, be sure you use the *current* magnetic declination - it does change with time, so the number printed on your map may be out of date. In the Sierra, 20 years ago when many of the maps were printed, it was 17 deg E. Currently it is closer to 14 deg E.

As you walk, keep track of streams, gullies, ridges, hilltops, knolls, and so on that are on your map. On trails, watch for trail junctions and bends in the trails. The contour lines help track when you are climbing or descending (use the compass to know which way you are headed - does this area slope toward the west, or toward the southwest, or maybe south? This can keep you from doing like the couple on Shasta did last week - they came down the north side of the mountain, rather than the intended south side).

This works not only in thick trees, but in fog, blizzards, night, and other times of limited visibility, such as in a canyon where you can't see the hilltops.

There are whole books on this, so what I have outlined is barely touching the surface. It isn't really as complex as it sounds. It just takes practice (which orienteering events will give you).

3:41 p.m. on June 27, 2008 (EDT)
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Thanks, Bill, for the info. So when you say the government topo maps are inaccurate, what do you mean?

4:18 p.m. on June 27, 2008 (EDT)
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Most of the USGS maps I use here in Michigan are more than 20 years old. In that span of time, unused roads and trails and buildings may virtually disappear; more commonly, new roads and trails may be built so that you just can't count on learning where you are from the intersections of the trails. The last time I used a top map to locate my position, about 5 weeks ago, I was lucky to be able locate a number of distinctive riverbends and other terrain features, including a ski lift located over six miles away. It helped that the area was hilly and we could see for miles from the ridges.

5:19 p.m. on June 27, 2008 (EDT)
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Another thing to do is to pre-plan your route by establishing handrails, backstops and catch points. A handrail is nothing more than a (somewhat) linear feature you may travel (somewhat) parallel to, such as a river, a ridge line or major road. A backstop is another major terrain feature that you know you're not going to move past. If there's a large valley, a dominating ridge or another identifiable feature that will keep you from deviating off course. A catch point is something similar, but serves as a checkpoint on your route. The low land where three draws form together, an intersection of a firebreak or a lake.

Like Bill mentioned, a good pace count really helps as well. If you start at 'A' and know by your map it's 1400m to your first catch point and you count 3 draws you're going to cross, at 300m, 750m and 1000m, by knowing how many steps (times your left or right foot hits the ground) you take for 100m and then where you are in your pace count, you can cross-check your topo (and visa versa) to verify where you are and where you have to go. This works really well when traveling at night, or through thick and/or terrain that seems it's on repeat, like the background of an old Super Mario game. Some tips there, though, are getting your pace count in a multitude of ways, i.e., open terrain, thick terrain, up hill, down hill, with your full pack, fatigued, at night and any other possible scenario you see yourself hiking in. Once you get more experienced, you can start estimating by time alone since you'll know that in this terrain, carrying this weight, feeling how you do, exactly how long it takes to hike a given distance such as a kilometer or mile.

11:02 p.m. on June 27, 2008 (EDT)
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Hi rdavis, You mentioned "terrain that seems like it's on repeat." The northwestern most part of my state, SC, is made up of repeating foothills. Looks like bubble wrap. It is hard to find unique terrain features for waypoints.
Fortunately we have lots of streams, unfortunately many are not on the map. I have been marking these on the map as I cross them, and then double checking myself with my GPSR, to "grade myself". Sometimes I am close, sometimes I am a bit off. OK maybe more than a bit.
I prefer to drive another 100 miles or so into NC where the terrain is more rugged, (and more appealing) because it is easier for me to navigate with the more distinctive terrain. Also there are much larger changes in elevation, which makes it easier for me to use my altimeter to double check my supposed location on the map in conjunction with the terrain I have in view.
I have also learned that contour lines don't really tell you if the elevation change is a slope or a vertical drop, which often forces me to take a detour.
I usually don't try to bite off too much since this is a skill I need to work on. I enjoy learning, and I like navigating in much the same way I like fly fishing, it is challenging, and gives me something to do besides just walk and look at blazes, but sometimes I wish I could walk across a trail or spot a blaze. HA-HA!

1:53 p.m. on June 28, 2008 (EDT)
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"I have also learned that contour lines don't really tell you if the elevation change is a slope or a vertical drop, which often forces me to take a detour." - the less space there is between the contour lines the steeper the terrain - cliffs are pretty easy to spot (unless, of course, the cliff in question is shorter than the distance represented by the contour lines ...).

As for getting oriented - the best place to start is at the trail head - keep notes on approximate distances and bearings - perhaps represent your route on the map with a pencil line - if you can manage to stay oriented you won't get lost! The worst time to try to figure out where you are is when it strikes you that you're lost -
One really nice thing about keeping notes on your maps is - if you find some place really beautiful - and you've noted distance and direction - you'll be able to get back there again - you can even share the beta with fellow hikers - no GPS required.

2:48 p.m. on June 28, 2008 (EDT)
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Map accuracy - Topo maps are, at best, 1:24,000 (1 inch on the map = 2000 ft) or 1:25,000 (most metric countries, a few US maps). Lots of maps are at smaller scales (fraction is smaller, so details appear smaller). In some countries, the best you can find are 1:50,000 or even 1:100,000 maps. They don't show all roads, streams, trails, buildings, etc, either because, as already pointed out, age of the map, or just omitted for simplicity. Although aerial photography and satellite imaging have now been used for a half century, along with stereographic contouring, lots remains to be done. Stereographic contouring sees the tops of the trees, which means the contours are often smoothed out (trees grow taller in drainages, and you can't see through the trees, especially our 200-300 foot tall redwoods in the local hills). There are some methods that have been developed to see through the trees to the underlying hard ground, but these are not really on line, and the US is large enough that it will probably be close to a century before the remapping is done (by which time, erosion, floods, hurricanes, tornadoes, and sea level rise will change everything anyway). Even so, the coarseness of the contours hides cliffs (a 30 foot cliff is hard to see on a 40 foot contour interval map, but it sure hurts if you walk over it), and steep gullies and ridges are often "softened" by the coarseness of the plot. Orienteering maps are frequently 1:10,000, and mapped by actually walking the area, making the subtle corrections as the mapper proceeded.

So those are the "natural" errors. A lot of maps still have the old "transit and chain" surveys (meter-level GPS surveys are still in their infancy, and mostly have been used on roads, not yet the backcountry trails, much less off-trail). The map publishing accuracy standards are that, for surveyed locations, the map will be accurate to 1/50 inch (which is the diameter of a 5mm pencil lead, or 40 feet on the ground) and the elevations will be good to 1/2 contour interval.

Orienteering maps often show boulders that are larger than a meter tall, stumps, fallen logs, and lots of vegetation detail. USGS maps only show "harvestable" forests, and do not really indicate the areas of open grassland, rocky ground, "runnable woods" (widely spaced trees), "fight" (vegetation you have to fight your way through, which in this area is usually characterized by plants with groups of 3 shiney green leaves), and other fine detail that are indicated on orienteering maps. Things like clearings and vegetation boundaries can be a great help in navigation, certainly in the return trip (if you have made notes).

And then there are the infamous errors that occasionally crop up, and sometimes don't get corrected for a long while. Back when I started a lot of Sierra off-trail wandering, I encountered a place where a ridge was indicated, but none existed, and several places where a stream was indicated by the blue line, but the expected ravine or gully was crossed at right angles by a tall ridge. More recently, the 15 minute quad for the Dardanelles area of the Sierra (near Sonora Pass), the names of a series of side canyons were displaced upstream by one (this is noted in one of the guidebooks to the area, and was a bit confusing when you came across a trail sign pointing up the stream branch that did not match the map).

Thing is - study all the maps and guidebooks you can before the trip. USFS trail maps are generally pretty good on the trails, though not on the contours. Most USGS topo maps are pretty good for the topography, though a bit sketchy on the names. If you keep track of where you are on the map as you go (keep the map in your hand and your thumb on where you are!), the maps are pretty good. Just be aware that there are some inaccuracies, and there are limits to the accuracy of plotting onto the paper. At the same time, the paper maps are far superior to the downloadable maps in GPS receivers.

3:35 p.m. on June 28, 2008 (EDT)
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You have asked a very good question. One that has been answered well. These are just my thoughts thrown into the mix. I hope it all works out well for you.

Rdavis makes good points about natural features and preplanning.
Preplanning works very well. Read-reading the map-over and over till you can see features, and can plan your route according to the natural features. You will also memorize these features so that when you are in the field(woods) you should remember that the creek/river to your right side has a little crook/kink in it. That feature alone can help you to find yourself on the map. As for cliffs, steep hillsides, or better yet, steep hillsides with a little hollow or irregular shape these also can show you where you are.

Remember, if you can not see terrain features, you have to move to or along the features until you can find yourself.

The more information you gather the better and easier it will be to find yourself on the map. You may not be able to get the pinpoint accuracy we all want but you can always work to tighten the accuracy from here.

If you are not sure of what you are doing, start in a large neighborhood park and start to look at the land differently. Say to yourself that you want to move a cart by yourself through the woods. I know it sounds corny. You will very quickly start to look at the woods in a different light. You will start to see features as I want to go there, or I want to avoid that. Even if you avoid all the places they can help to identify your position on a map.

This is a skill that takes time to develop.
Even in Canada the Topo’s are not quite up to today’s date in recording information.

8:13 p.m. on June 28, 2008 (EDT)
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Sorry Fred, I should have been more clear, I did mean the distance between contour lines. Especially at 40 ft. intervals. Sometimes the drops are not completely vertical, but I don't try to climb down them since everything here is damp and slick, plus my dog has no thumbs! But I am convinced he can either hear or smell water, maybe both.

7:26 a.m. on June 29, 2008 (EDT)
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go to

Print out some of the grid overlays onto overhead projection film.

with your GPSR, your overlay and Topo map, you'll be able to navigate to a point or identify your present position with a 100 yard accuaracy.

2:48 p.m. on June 29, 2008 (EDT)
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trouthunter - your dog lacks thumbs? How's he hold his beer????

No worries - small cliffs can be tough to identify using a map - it is fun, though, to mark your route on a map - especially for "big" trips - years later you can take the map and any photos you took during the trip and - to some extent - re-live the experience.

12:04 p.m. on June 30, 2008 (EDT)
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Keep in mind that you can use a computerized mapping program like National Geographic's Topo! to draw in your intended route, print the route on a single sheet (none of the route ending up on 2 to 4 separate sheets of paper), get a 3D flythrough to get an idea of the terrain (the 3D views are still a bit primitive, due to coarseness of the data), and afterward attach your photos to points on the map for a slide show. Really long trips, like thru-hikes, still require a huge amount of paper, no matter what the map choice.

1:50 p.m. on June 30, 2008 (EDT)
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Thanks, everyone, for your responses. Bill, after your comment about map accuracy, I checked one of the trail maps I used recently and discovered that the trail location on the map was indeed inaccurate. For example, the location where the trail forked on the map was on the opposite side of the forest road than it is in real life.

So what rexim said about not being able to use the map to find your exact location along the trail was true in my case. No wonder the map didn't match what I was seeing on the ground.

So, how do you know if the map you're using is accurate or not? Date?

8:12 p.m. on June 30, 2008 (EDT)
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The only real way to check the accuracy of the map is to get out there and use it. Sometimes there is a reliable guidebook to the area (note I said "sometimes" - there are some notorious guidebook errors, too). Keeping track of your location all the time helps get around the map and guidebook errors. Talking to the local land manager (ranger for state and federal parks and forests, similar for BLM) can often get good info. There are websites that post map corrections or GPS-derived tracks (NatGeo's Topo! has such a page, and their Trails Illustrated map series have field-checked trails on them).

Mainly, it is just a case of making note and keeping track of landmarks as you go, and talking to people familiar with the area (other hikers, rangers, local guides and packers). These people will have current information that you should have anyway - passes blocked by snow or rockslide, streams that are easily fordable or impassable due to high water, bridges that are washed out, current info on dangerous wildlife (including 2-legged "herbal" farmers who carry and use "heat"), availability of water at the "usual" watering and camp sites, etc etc. Take notes on your map, as has already been suggested.

Oh, sorry, you asked about date of the map ....... excuse me while I get up off the ground from laughing so hard. The date label only tells you when someone quit working with the data from a survey that applies to some random part of the map, because they had a publishing deadline.

I guess I shouldn't be quite so hard on the map folks. The USGS does a pretty good job with maps in the 50 states and the territories - far better than 90 percent of the countries in the world and equal to the other 10 percent. Given the limitations of time, personnel, funding, and the continually changing landscape (new roads and trails, re-routing old roads and trails, abandoned roads and trails, floods, erosion, volcanic outbursts [I have before and after maps of St Helens, to commemorate my before and after climbs of that hill], etc etc), they actually do a superb job. It is hard work, even given modern surveying tools. If you want to see how bad maps can be, try some of the 3rd World countries. There is still a lot of this planet that remains to be mapped (a friend of mine is engaged in a mapping project in Antarctica - he has spent the past 4 or 5 daylight seasons clambering all over just the Sentinel Range, carrying a survey-quality GPS receiver to as many peaks and passes as possible, then post-processing the data to get the accuracy to an acceptable level. He and his team are doing a superb job, under really difficult working conditions. But at least, he doesn't have an African or South American jungle to contend with, or some huge desert - the Sahara still is not completely mapped).

6:56 p.m. on July 15, 2008 (EDT)
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hey everyone, this is a great thread. I wrote a how to guide on exactly this topic:

I hope you all find it useful.


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