Techniques > Navigational Questions & Answers

On Latitude & Longitude: why the confusion?

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Pete McK:
Great article Lyle and something I feel Trail mag should continue championing, if you need any help I would be more than willing to help - seriously - as I know of and have tasted most of the 38 microbreweries beers in the Lake District.

Paul Hitchen:
I like the free app in Langdale called LangD Ale

It shows you the pubs in the valley and what beers they have on.

It even has a goto pub button

.... Genius ....


captain paranoia:
A grid system is no more artificial than an angular coordinate system.  One is a system of linear measurement of distance, and the other is a system of measurement of angles; both are measurements of 'the real world'.  Both have their pros and cons, and both can be used for navigation; they don't need to be mutually exclusive.  You can convert one system to the other, although the trigonometry is a little tedious to do by hand.

Whichever system you use, you need to be able to relate your measured position relative to the ground, and relative to a map that tells you about the landscape around you, and especially about the landscape out of sight, either due to obstruction by nearby terrain, or due to dark or atmospheric problems.

Grid references are a tool to identify and refer to positions on a map (and be transferred to positions on the ground), hence the name 'references'.  I doubt if many people actually navigate by them.  A regular, linear grid allows these positions to be measured using a simple ruler (aka a romer).  An angular grid drawn on a map with a linear projection (e.g. UTM) doesn't allow this simple reference reading, since the angular grid lines are not straight, and the spacing isn't uniform.

Navigating along a route leg does indeed involve polar coordinates, being range and bearing, but that bearing cannot easily (without recourse to trigonometry) be determined from the angular coordinates of the two end points of the leg; the magnetic bearing of a leg 1degreeN by 1degreeE is considerably different starting at a point on the Equator (about 45 degrees) than it is starting at a point on the Arctic Circle (about 22 degrees), due to the variation of the longitude line spacing with latitude.  Whether the grid is linear or angular, provided the map projection is linear, you can measure the bearing along the leg to well within the accuracy of your compass (the distance and angle errors introduced by the projection are very small), so the grid used is of no consequence.

As I've said a number of times on MNF, I rarely use a compass when navigating, using terrain-to-map association instead to keep track of where I am, and where I want to go.  Much of the time, I'm just mentally logging my position on the map, having looked at the terrain and chosen where to go, rather than looking at the map and then trying to figure out where that is on the ground.

> I posit that by looking at the world in 3D, {Space-Time} on a globe,relative to the Sun, Moon, & Stars, along with the motion of shadows [all of this is from making sundials], rather than wandering about detached from these factors, it ought to be less likely that one become lost.

It's true that those methods can certainly be used to help navigate, if you're lucky enough to be able to see the sun, moon and stars.  In the UK, sadly, we're not always that lucky...

Paul Hitchen - The best App that I have downloaded all year - thanks for this ;) Have also seen a poster map, with all of the breweries detailed, including telephone numbers and visitor times, I will see if I can get hold of a copy.


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