web mapping - Is latitude / longitude a universal coordinate system?

I hear people complain:

my biggest gripe with google spatial apis is that they hide the fact that latitude/longitude is not a universal coord system

My question is Is latitude / longitude a universal coordinate system? What are the implications if it is not?

Answer

It depends on what you mean by 'Universal Coordinate System'. If you wonder whether most Professionals understand Latitude and longitude, well in that case it is pretty much universally understood.

But if you ask, whether it is used by everyone, then the answer is a resounding, No. There are many reasons why people use projected coordinate systems instead of a Geographic Coordinate system, such as:

• Pre GPS, it was far easier to find the location with more accuracy in a local Projected Coordinate system, than a Global Geocentric Coordinate System. This was not only due to variety of control points available in a Local system, but also because it is computational easy.



• It's far easier to calculate distances and bearings in a projected coordinate system.


• Web Mercator has become the defacto projection for web mapping, because it is a projection which is locally conformal, i.e. it preserves the shapes and directions at large scales.


• And lets not even get into legacy and statutory reasons for using projected systems.

Amongst those people who use Geographic systems, there may not be universal agreement about what reference system to use. There are different datums that one could use, as well as different prime meridians that could be used. This comes into play, if you are searching for long lost treasure, or if you go to the Greenwich Observatory with a GPS and wonder why you are not at 0 longitude