Let's say you decide to go car camping. You don't bring a map, because the plan was to just stay in one place and relax. Someone in the next campsite tells you their young child wandered off and has been gone for a couple hours and they'd like you to help in the search. Since you weren't planning on hiking, you didn't bring your GPS, but you do have your compass. Can you navigate safely without a map and just a compass?

The solution is really easy. It does take keeping good records of distances and bearings. But just log them during the search. No need to know exactly where you are until it's time to come home.

At the end of the day, take some parachute cord and lay out your travels on a flat spot. Or use sticks. Whatever works. Just lay it out accurately using the Magnetic headings you followed.

It may look something like this. At the end, you have a bearing and distance to the start.



The technique is described well in this book.

It's not a technique I'd recommend without practicing in a safe environment first. But it works very well.

On the ocean, this is called dead reckoning and the etymology is that it comes from deduced reckoning.

OF course there are lots of jokes about Dead reckoning.

And you are right---the keeping of the records is absolutely essential to any success with this method.

You can start by writing: SHip's Log, Star Date....

I can tell you from researching more than a few shipwrecks that dead reckoning is a very common cause thereof.

Frankly, the situation proposed is highly hypothetical. Would you not at least have a road map? If I ever were in this situation I would 1) differing to searchers who were properly equipped with basic gear, or 2) structuring search areas based on terrain features - "you guys search down this creek to the highway; be sure to check the creek bottom as well as both slopes. The rest of us will scour the west flank of this hill to the west - etc.

The advisability of option #1, which is rather wimpy, would depend upon the terrain and its potential danger for unprepared searchers.

In any event, it would be smart to summon backup promptly...

Flying in the air it's called dead reckoning too but I don't think Gershon is referring to that. There is no map to compare to in his scenario.
By knowing your starting point and taking a compass bearing, and then knowing your approximate rate, you can run the reciprocals back home. (assuming you have a really good memory or wrote everything down) I've always got a compass on me and in the car. My iPhone has a dandy one. I sometimes plot a course across big crowded parking lots to and from my car, or across big crowded convention centers. Lakes are good for simple compass bearings when you are trying to meet up with people...."I'm 245deg off the boat ramp to the opposite bank." No GPS or map needed.
Knowing the direction from which you came, is the first step in getting back home.

Well, the system is deduced reckoning. Yes, the situation is wimpy, but actually getting help takes about 24 hours in this area. I know that because I called the sheriff's office and asked. Individual situations may vary, but each hour is another mile or two a kid can easily wander.

It's exactly the same as flying, except you can stop and gather data and take time to think. I've been practicing it in the prairie where there are lots of obstacles to walk around and I find I'm always within 3% of the distance walked. 150 feet error in a mile of walking.

You don't need to know your starting point. I'm "here" and I want to get back "here." That's good enough. Everything is relative to that point.

Deduced reckoning doesn't ignore other factors. The normal lay of the land is a big hint to where you must be. Looking from the top, a big hill generally looks something like looking down at a circle of shoes with the heels towards the middle. Draw, spur, draw, spur, etc.

The biggest challenge is estimating distance. Pacing works well, but requires very short legs. Generally around 100 to 150 feet. It's real time consuming to write all that down and resolve. I find I can move around a mile and a half an hour doing this. It is extremely accurate, though.

But there are other ways. Stretch your arm out and point your index finger and middle finger putting the distant object on one finger and the other finger on an object to the right or left of it. The horizontal distance will be about 15 times your distance from the object. It doesn't even matter if your multiplier is wrong if this is the only method used as the scaling will work out in the end.

An object 5 degrees off from a distant object is 1/11th of your distance to it. Pace it off when you get there.

It's not something I'd recommend to someone who doesn't really practice a lot. First starting in a very safe area where it's impossible to get lost. Then with a safety observer using a map and GPS.

With two sets of ranger beads properly made, nothing even needs to be written down. You will always know where you are relative to the center and any other point you might choose to get to. I'm still working on that one.

Thread drift alert: Where in an area accessible by road would it take SAR 24 hours to respond? That sounds rather flaccid.

I guess going into that environment, I would be sure to have amps, etc. and be at least reasonably self-sufficient. Which is actually a pretty good thing.

I have been impressed with the accuracy of pedometers that claim to be able to distinguish random motion from actual strides. In any event, you need to nail down the length of your pace rather accurately. Counting paces is much better than just a WAG as to the distance covered.

Really, the SAR situation was just an introduction and not meant to be the focus.

Navigating by dead reckoning in a safe environment (say inside a loop of roads) can be a lot of fun. It's just another way of enjoying the woods. It might also be handy to get past that half mile stretch where the trail is covered with some snow and it's not marked. Knowing how to get back to where you started with practiced skill might help.

I've done some underwater navigation, but never got very good at it. I'd usually just give up and pop up to the surface to see where we were. Worked every time.

Yeah--and dead reckoning in the air or on the water also involves estimate set and drift...the air and water are moving relative to the land underneath...

It is very difficult to get good at underwater navigation. I usually employ the popup technique...I still vividly remember an occasion where I was confused, but thought I was close, so started up. The first thing my hand touched as I broke the surface was the dive step. I tried to convince my buddy that this was routine, all in a night's work, etc., but I don't think I succeeded....

Drift isn't as bad in the air as one might think. At least if you can see the ground. Just line up two distant landmarks along your course. If the close one moves to the right turn right to stop the drift. Then turn right again to correct course and then turn left to the heading that stopped the drift.

The same works on the ground with landmarks surprisingly far away. It will correct a tendency to always go right or left around obstacles.

As you get near the first landmark, select a third to continue the process.

You can use this in the "find the truck" scenario. On the way out pick two high landmarks to line up on the way back. Be sure to write down the bearing. If you are planning a loop, find a bearing on two obstacles that will line up at the end of the loop.

This stuff takes a lot of practice, but that's part of the fun.