Wednesday, May 1, 2019

Geographic Coordinates Order - Latitude Longitude OR Longitude Latitude

There is this frustrating inconsistency in working with geospatial data as to whether an array of numbers like this "9.071, 7.499" means Latitude, Longitude OR Longitude, Latitude?

I have personally wasted valuable time when am using a new GIS tool trying to figure out the right coordinate order recognized by the tool.

Obviously, some GIS platforms use Latitude, Longitude while some uses Longitude, Latitude. The question now is which is the correct coordinates order? This is an opinion with no right answer. Vocal and written geographical theory favors Latitude, Longitude. Numerical and software prefer Longitude, Latitude.

It common to describe a location as *the Latitude and Longitude of ABC is "9.071, 7.499"*, thereby mentioning Latitude first instead of the Longitude. However technically speaking mathematics, Latitude represents Y coordinate while Longitude represents X coordinate. So Latitude, Longitude implies Y, X while Longitude, Latitude is X, Y.

If you include altitude or height (Z) of ABC location the two coordinates ordering above will read: Latitude, Longitude, Height (Y, X, Z) and Longitude, Latitude, Height (X, Y, Z) respectively.

The most common ordering is XYZ - Longitude, Latitude, Height. However, if you decide to adopt YXZ - Latitude, Longitude, Height you could still be right. The most important thing is for you to know the right order you need when working with a GIS platform especially a new one you haven't used before.

As an example, Google GIS products (such google maps, google earth, etc) use the format YXZ - Latitude, Longitude, Height. ESRI ArcGIS and QGIS adopted the format XYZ - Longitude, Latitude, Height.

This coordinate "9.071, 7.499" on Google maps is the Y, X- Latitude, Longitude values of "Millennium Park (Wupa River)", if you change the order like this "7.499, 9.071" (i.e X, Y - Longitude, Latitude) it points to a different location from the intended location in this case an Unnamed Road.

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