Author Topic: On Latitude & Longitude: why the confusion?  (Read 7746 times)

MoonMan

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On Latitude & Longitude: why the confusion?
« on: September 15, 2013, 04:37:44 AM »
having read that some are uncertain about how Latitude & Longitude work {something that I was taught in Primary School}, I present this simple explanation: the Earth rotates about its axis, the Axis of Rotation, or Longitude, is also known as the Meridian; the Plane of Rotation, or Latitude, is parallel with the Equator, which is the Null point of N or S, the Poles being at 90 degrees thence. E & W are, by International Agreement, measured from the Greenwich Meridian, formerly Teneriffe, Hamburg, Paris, Beijing, or elsewhere. Grid Reference is only of use if one have a map; Navigational Astronomy gives its results in terms of Degrees, Minutes, & Seconds, Knots are the measure of Seconds of Arc traveled one hour. eg: the square root of height in Feet equals Distance seen in Knots, or Minutes of Arc.  A protractor will assist one to visualise what is intended.
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captain paranoia

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Re: On Latitude & Longitude: why the confusion?
« Reply #1 on: September 16, 2013, 01:17:21 PM »
One simple problem I think people have with lat/long is the order in which they're given; up/along.  This is the opposite to Cartesian coordinates used in so many other fields and forms, including grid references.

Lat/long certainly has its uses (especially in astronomy...), but for land navigation using linear measures, a linear grid system using a suitable transformation makes life a lot easier.

MoonMan

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Re: On Latitude & Longitude: why the confusion?
« Reply #2 on: September 17, 2013, 05:18:36 AM »
Cartesian Coordinates have polarity: that is, Above /Below; Left/ Right; Ahead/Behind. That is to say,all values are multiples of the Square Root of Minus One . thus, x2 = w2; x2 + y2=w2; & x2 + y2 + z2 = w2.
 This was first noticed by William Rowan Hamilton,of Dublin,who discovered Quaternions.,who used these as products, rather than sums.

On the ground, think of where There is, in relation to Here. The shortest distance is always w.
« Last Edit: September 17, 2013, 08:48:36 AM by MoonMan »
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Lyle Brotherton

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Re: On Latitude & Longitude: why the confusion?
« Reply #3 on: September 20, 2013, 11:06:36 AM »
For the sake of clarity for all forum members

On land, sea and in air navigation Latitude and Longitude is the universal coordinate system used the world over. All air-traffic and maritime vessels use it, plus many of the emergency services.

For us as land navigators it can be used when we are in regions of the world where there has not been a national grid system established (such as the British National Grid).

For land navigators involved in SAR (Search & Rescue) the understanding of how to take and give Lat/Long coordinates is important, as fixed wing aircraft, as opposed to UK SAR helicopters which use the BNG (British National Grid) use the Lat/Long system and if an area designated to be searched is being conveyed to this type of flight Lat/Long coordinates should be used.

In summary:

Latitude
• All lines of latitude run horizontally around the globe
• lines of latitude run parallel east to west
• used to express how far north or south you are, relative to the equator
• shows your location in a north–south direction
• latitude is an angular measurement in degrees from 0° at the equator (low latitudes) to 90° at the poles (+90° N for the North Pole or --90° S for the South Pole)
• lines of latitude are always the same distance apart – 1° = approx. 110 km
• abbreviated to Lat
• sometimes called parallels.

Longitude• all lines of longitude run vertically on the globe and converge at the poles
• start at True North
• shows your location in an east–west direction
• longitude is given as an angular measurement ranging from 0° at the Prime Meridian (also known as the International Meridian at Greenwich, England) to +180°E and
--180°W
• abbreviated to Long
• sometimes called meridians.

Long/Lat is measured in degrees (°), minutes (') and seconds (").
Where 60” (seconds) = 1’ (minute) and 60’ (minutes) = 1° (degree).
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MoonMan

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Re: On Latitude & Longitude: why the confusion?
« Reply #4 on: September 21, 2013, 05:16:35 AM »
So, I gather that the problem lays in whether one think in Grid or Polar Coordinates: grids exist only on maps & street plans, they nominate a square by its edges. In the real world, as opposed to a nominal one, one uses the Earth's axis as a reference, there is nothing "imaginary" about it, it is only invisible. The Latitude, Longitude, & Altitude assume that the Earth is a perfect sphere, for the purposes of applied mathematics, termed Geocentric. & is Nominal. This is further adapted to take in the reality of an Oblate Spheroid, termed Topocentric, & is much close to the Real.
The difference is that the exact location, in the cross-hairs of lat. & long.,rather than pigeon-holed in a box.
Consider: one does not travel along horizontal grid line A till he reach vertical grid line B, but finds the direct route: A2+B2=D2. Likewise, the angle arc sine B/D is the  outward Course, the angle arc sine A/D is the return Course. It matters not that one ascertain the Course Angle by Grid or by latitude & Longitude, the result will be about the same. The Earth is not flat: maps are. One needs to be able to imagine his place in Space-Time, & refer his map to that, not vice versa. The real map is in one's Noticing & Recollecting the surroundings, the nominal map is on paper or in a computer programme. Very handy to study before going, but inattention to surroundings can lead to one being misled by the map.
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Hugh Westacott

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Re: On Latitude & Longitude: why the confusion?
« Reply #5 on: September 21, 2013, 02:14:53 PM »
Moonman wrote:

<The Earth is not flat: maps are. One needs to be able to imagine his place in Space-Time, & refer his map to that, not vice versa. The real map is in one's Noticing & Recollecting the surroundings, the nominal map is on paper or in a computer programme. Very handy to study before going, but inattention to surroundings can lead to one being misled by the map.>

I read your posts with interest, Moonman. I'm not clever or well enough informed to follow the mathematical discussions between you and the noble captain, but I am intrigued by your metaphysical view of the world. It seems to me that when we are considering maps that are used by walkers, artificial grids, such as the British National Grid, are far superior to latitude and longitude because they are much easier to use and they facilitate the use of romers.

The concept that the real map lies within one's head does not work for a pedestrian fellow like myself. Last week, I spent some time checking the condition of the public rights of way in three parishes in North Buckinghamshire (for our overseas members a cvil parish is the smallest local government unit in England and Wales and may be described as comprising a village and the land in the immediate vicinity). These three parishes contain a total twenty miles of public paths that form a dense interlocking network that crosses numerous irregularly shaped small fields. Many of these paths, although waymarked at the field boundaries, are little-used and are not always visible on the ground. To complicate matters even further, the terrain over which these paths run is predominately flat so, in most cases, it is only possible to see as far as the hedges that enclose the field.

In such circumstances, I find it impossible to carry in my head sufficient information to enable me to navigate more than two fields ahead without consulting the map. Moreover, some paths run diagonally across a field and then divide into two routes in the middle of the field. As far as I'm concerned, the map is a representation of the real world as it existed at the time of the survey.

Thank heaven for accurate maps and the micronavigation techniques that allow me to follow the paths accurately.

Hugh

« Last Edit: September 21, 2013, 02:22:38 PM by Hugh Westacott »

Lost Soul

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Re: On Latitude & Longitude: why the confusion?
« Reply #6 on: September 21, 2013, 04:35:00 PM »
Moonman wrote:

<The Earth is not flat: maps are. One needs to be able to imagine his place in Space-Time, & refer his map to that, not vice versa. The real map is in one's Noticing & Recollecting the surroundings, the nominal map is on paper or in a computer programme. Very handy to study before going, but inattention to surroundings can lead to one being misled by the map.>


Put simply, study the map before you set off.  Memorise any prominent markers / features you should encounter on your way and always read the ground to the map, not the other way around.  Oh and make sure you are continually reading ground to map.

MoonMan

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Re: On Latitude & Longitude: why the confusion?
« Reply #7 on: September 22, 2013, 12:54:32 AM »
Hugh,I did not say don't use a map. My point is that many folk do get lost,with or without a map,because they do not make the connection between Here,which is where they are on the ground,& There,whether it be where they set out from or where they set off to. I posit that by lo 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. I have had many happy explorations with the compass left in my pocket, the map & knowledge of what to notice being adequate. if one has no map, it is wise to take notes & make one as one goes. The places that I tend to roam in have only the track in, the rest is finding a way. AGAIN, I say, the tendency to rely upon a gridscape leads one astray in places where grids do not exist. As in "thinking outside of the box": there is no box. Here is where you are, what is the Distance & Direction of There? Polar coordinates. House number ##, XYZ street: route ordinate; AB 12 CD: grid coordinates. Triangulation, used to make maps, & to locate position on maps. Used to make a mental map of one's journey.
Lost Soul has got it.
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Lyle Brotherton

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Re: On Latitude & Longitude: why the confusion?
« Reply #8 on: September 22, 2013, 07:16:41 AM »
For the benefit of general forum members and visitors to this community.

Whilst Moonman's opinions are interesting, you should never venture into the great outdoors WITHOUT a map and compass unless you are absolutely sure of the weather forecast and have both a comprehensive knowledge of the area and detailed understanding of the hazards therein.
« Last Edit: September 22, 2013, 05:09:53 PM by Lyle Brotherton »
“Opinion is the medium between knowledge and ignorance” - Plato

Lyle Brotherton

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Re: On Latitude & Longitude: why the confusion?
« Reply #9 on: September 22, 2013, 07:38:36 AM »
Sounds great Lost Soul, I share a similar passion for hops, barley and malt, especially when all mixed with yeast ;)

For last month's Trail Magazine (Sept 2013) I met up with their highly competent Editor, Simon Ingram, and great photographer, Tom Bailey - both thoroughly decent blokes too :) As they too share this passion for the aforementioned ingredients when mixed and they have created an inspirational beer trail in the northern Lakes, in England.

I will ask their permission to publish it here and would strongly encourage others to dedicate time to creating and sharing beer trails for their local areas :)

I have started working on one for the Scottish Borders which will include the ales from the excellent micro-brewery at Ancrum!
“Opinion is the medium between knowledge and ignorance” - Plato

Pete McK

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Re: On Latitude & Longitude: why the confusion?
« Reply #10 on: September 23, 2013, 09:54:51 AM »
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

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Re: On Latitude & Longitude: why the confusion?
« Reply #11 on: September 23, 2013, 09:59:50 AM »
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

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Re: On Latitude & Longitude: why the confusion?
« Reply #12 on: September 23, 2013, 06:27:51 PM »
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...

Callum

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Re: On Latitude & Longitude: why the confusion?
« Reply #13 on: September 25, 2013, 12:47:34 PM »
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.