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Training Day #3 – Solutions (kind of)

/in /by

I guess by now everybody who was planning to go through the little homework assignment has done so by now…

Each of the problems I posted was based on a situation I have encountered, either on my own tours.

Estimating the accurate location of an unknown point by using bearings from / to other, known locations is called position resection or intersection, a method that is worthwhile to be familiar with even in the modern day of GPS devices.

The issue with mixed interpretations of GPS coordinates has come up multiple times in search & rescue, for example during a SAR operation on Grímsfjall last year, and I wrote a more detailed blog post about this at the time.

Counting steps and developing an intuition for distances covered is an important skill for anybody who plans to reduce their reliance on GPS devices, and with phones and watches counting steps fairly accurately even in standby and low power modes, that is a cheap way for estimating distances and saving your battery at the same time.

Here is a video where I’m going through each of the problems in turn.

Thanks to everybody that participated, and I am looking forward to doing more of this very soon. Next time it will be outside!

August 31st, we’ll meet at the turnoff from the Ring Road towards Heinaberg.

Training Day #3 – Navigation Planning & Theory

/in , /by

Alright today is the next training day in my schedule!

This one is work friendly since everybody can just do it at home in their own time. It is primarily a precursor to next month, where we’ll put these things out into the field… the idea about this episode is that some aspects of working with maps, GPS and compasses are best practiced at home first where you can really dive deeper into the subject, there’s no wind or rain messing with your paper maps, and so forth. So it is really just a bit of “homework” in the form of a series of little questions and problems, to have food for thought to build up our intuition about our various navigation tools.

Of course my own thoughts on each of those aspects will be available too; either as a separate post here or as a video – but since I would love everybody to give it an honest try themselves first (and those are problems that I also need to work through myself first!), that will come in a few days.

… here we go:

1. Oh! Big crevasse!

I recommend to download & print this PDF map I prepared, but if you don’t have a printer any other paper maps of the area will work just as well of course – the PDF will still help you see where each of the points are, and I included a compass rose with true and magnetic indications that should help solve this problem.

You’re out with a group of friends, practicing some late summer mountaineering skills in the mountains around Jöklasel when you notice a really big crevasse that seems to be close to some of the snowmobile tracks. You can see it very clearly from your elevated viewpoint but aren’t sure that it is as obvious from ground level, so you want to make a note of its coordinates to share with the companies operating there. Fortunately you have a GPS device with you, and you store the two points where you’re making sightings of the crevasse.

At first you can see it from close to the ridge between Miðfellsegg and Birnudalstindur (point 1 on that map), and your compass shows you a bearing of 352° to the crevasse. Later on you can get another good view of it from some lower slopes, at point 2, and from there it is at a bearing of 316°.

Once you are home, you realise that your new compass was not yet adjusted for magnetic declination.

  • Draw the location of that crevasse on the map.
  • How far off would the location be if you are using true north vs. magnetic north?
  • Can you really read off bearings with single-degree accuracy?
  • Estimate longitude and latitude as accurately as you can.

2. A certain degree of accuracy

You are guiding a group of hikers from abroad exploring Eldhraun, north of Laufbalavatn. There is another group from the same trip who are all highly experienced hikers and decided to wander about a bit on their own. Cell signal doesn’t seem to be reliable but everybody is carrying UHF radios and the other hikers brought their own GPS device too.

Around noon the other group radios in that one of them lost their phone and if you could come help them search for it. Unfortunately reception is really poor, and they only manage to read off each digit of their latitude and longitude before the connection breaks off.

All you can hear is that the latitude digits are 6-4-0-2-2-7-9, and the longitude is 1-8-0-1-9-3-4.

  • Is that enough information to pinpoint their location?
  • How much of a possible error would you expect if all you know are those digits?
  • How many meters does one minute of latitude or longitude roughly span in Iceland?

3. One step at a time

You are crossing Vatnajökull on your way to Kverkfjöll, and you know there is a large crevasse south of Brúðarbunga that should be avoided carefully. From your current position, you know the best route is to keep heading northwest for another 1.5km, and then make a 90° turn NE.

To save battery on your devices during this long expedition, you are not using your phone or GPS watch to track your movements, and only activate your dedicated GPS sporadically. Unfortunately visibility is limited, and the terrain is too flat to judge your progress by altitude. Instead, you try to rely on other estimations as much as possible.

  • How many steps does it roughly take to cover this distance, with regular boots, snow shoes or cross country skiing?
  • There is probably not much else to keep your mind occupied anyway, but do you actually have to count those?