You are only located at one place at any particular time. I know what you’re thinking; “Thanks for that genius“.

Beam me upDespite this, did you know that you have more than one latitude, and for that matter, longitude too?

No? Well this isn’t as mystical as may first appear. We aren’t talking about Star Trek here, and even if you were beamed up like Scotty, you would still only be in one place at any single moment.

So what’s the confusion? Let’s start off by discussing a few details.




Your paranoia is justified

You are being watched

Gone are the days where a big eye peering through a twitchy curtain was the main source of prying on your whereabouts.

Your phone company, laptop, social media networks, search engines, downloaded applications and who knows what else all want to know where you are. There is CCTV monitoring your every movement as you walk through the city centre, traffic cameras checking your speed and private security watching that you don’t stray where you shouldn’t venture.

It seems that everybody and everything wants to know where you are and what you’re doing.


How do satellites track you?

It’s a process called triangulation, or trilateration as the purists would call it. Using geometry the global positioning system can work out your exact location. It’s relatively elementary in principle, but mathematically a little more challenging. If maths scares you, look away now. If you like a challenge, then see below:

For n satellites, the equations to satisfy are:

(x-x_i)^2 + (y-y_i)^2 + (z-z_i)^2 = \bigl([ \tilde{t}_i + b - s_i]c\bigr)^2, \; i=1,2,\dots,n

or in terms of pseudoranges,  p_i = \left ( \tilde{t}_i - s_i \right )c, as

\sqrt{(x-x_i)^2 + (y-y_i)^2 + (z-z_i)^2}- bc = p_i, \;i=1,2,...,n

What is latitude anyway?

……or a longitude, whilst we’re on the subject?

This is probably best shown by the use of a diagram, such as the one below. As can be seen, wherever you are, your location possesses a latitude and a longitude.

latitude and longitude

So what’s the point (of latitude)?

It may seem that this story has deviated from the original point, so it’s time the information was once again grouped. After all, the last thing we would want is to have our geospatial integrity questioned.

Here’s the facts; We know that:

  1. You can only be in one place at any single moment in time
  2. There are lots of things watching us and measuring our location
  3. Every point on planet Earth has a latitude and a longitude

Well, here’s the bit that I was waiting until the end to share.

There are multiple spatial reference systems, each of which has it’s own way of measuring where you are located. If you are located in the UK, a square map is often used to work out where you are, using a grid of Northings and Eastings that care nothing about the curvature of this wonderful planet. Google uses a spherical mercator projection based on WGS84 to locate you. There are many others that are cartesian, geodetic or projected in their manner. All long words, but anybody who has attempted to convert geospatial systems from one form to another will understand that it needs one’s full concentration.

The world is not flat

Unfortunately, it isn’t round either. Due to that strange phenomenon called centrifugal force, Planet Earth is effectively squashed into a shape known as an oblate-spheroid. This creates geospatial conversion problems that can not be overcome by simple equations.

So, what’s your latitude? Well, it turns out that each of us has many latitudes. It just depends who’s asking the question.

Ordnance SurveyUKDK use location, sometimes geospatially, to give data intelligence. When added as an additional ingredient to traditional services, it results in specific results that give an edge on the techniques of your competitors.

Pete Clark is the CEO of UKDK


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