The Mercator Projection
By: Jeff Vasishta
Tags: Routing Software, Electric Mobility, Maps, Routing, Electric Car

The Mercator Projection

Here’s a handy piece of trivia to parse out at dinner parties — the mapping system used in most modern electric vehicles zipping along Europe’s pristine highways was first developed in the 16th Century. It’s called Mercator Projection. The what?

Photo by Stephen Monroe on Unsplash

Named after Flemish cartographer, Gerardus Mercator in 1569 (yes, really!), The Mercator Projection was soon adopted as the go-to map for globe trotters. It managed the previously unfathomable feat of efficiently representing a three-dimensional entity, or to be specific, an ellipsoid, (the earth), on a flat, rectangular surface (a map). Mercator managed this by distorting the size of sections of the globe the further you got from the equator. Thus, most distorted are the North and South Poles. So, in Mercator’s representation, Greenland is the same size as Africa, when in reality Africa is 14 times larger. Mercator was considered to have cracked the Rubik’s Cube of the era and so successful was his projection that it is still being used today.

Why is the Mercator Projection used by Chargetrip?

One of the key successes of the Mercator Projection was that it was able to preserve rhumb lines — the imaginary lines on the earth’s surface, cutting all meridians at the same angle, used as the standard method of plotting a ship’s course on a chart. The good news for EV drivers is that these rhumb lines serve as the basic tenets for all navigation. However, there are differences in plotting a ship’s course across the Atlantic and a car’s navigation to the next charge station and so modifications have been made since Mercator’s day.

Charge map with pre-rendered & filtered stations and clusters

Vector Tile Service

The rhumb lines give way to tiles or a Vector Tiles Service to give it its proper name, when zooming in becomes necessary to plot driving routes, as with a car’s navigation systems. A map is divided into equal square tiles, with the entire earth fitting into a single tile at a zoom level of zero. Tile sizes increase by a factor of four, both horizontally and vertically, each zoom level you go up so that a zoom of 1 would have 4 tiles and a level of two would have 16 tiles, etc. Using tiles is necessary not only to allow detailed routing but also to save space and data and thus allow speedy searches, with each tile only containing the data needed for its particular section.

Pinpoint accuracy

It is possible to achieve pinpoint accuracy by continually zooming in. By a zoom level of 17 or 18 individual buildings occupy much of the screen. This is achieved by using X and Y coordinates based on the longitude and latitude of a building or point being searched.

Charge station icons

Web Mercator

To support zooming, a new projection, designated by the European Petroleum Survey Group, was created in 2005, which was still based on the Mercator Projection and is commonly referred to as “Web Mercator” or “Spherical Mercator.” While the new projection distorts size in the same way as Mercator’s projection did, the further away you from the equator you go, it simplifies the equations to use a spherical approximation for faster calculations.

Conclusion

There’s a lot to the saying, ‘If it ain’t broke don’t fix it.” That’s why the Mercator Projection of mapping has been used for centuries. However, to accommodate technology and allow meticulous accuracy in navigation systems and, in the case of Chargetrip, to map charge stations, modifications have been necessary. By using the Vector Tile Service, regardless of your location, you’re a tap of a screen away from knowing the exact location of the nearest charge station to your EV.