Web mercator projection

On the other hand, because of great land area distortions, it is not well suited for general world maps. For example, a Mercator map printed in a book might have an equatorial width of Big decisions are often reliant on spatial analysis.

But if analysis of data is being performed it is a sin to use the Web Mercator. It is possible to retain at least one of these properties but not all. Uses[ edit ] The Mercator projection portrays Greenland as larger than Australia; in actuality, Australia is more than three and a half times as large as Greenland.

A Mercator is a conformal projection and as such preserves angles shape as seen by the circles in the figure below but distorts size and area as you move away from the equator. Many different methods exist for calculating a.

Mapsand others use a variant of the Mercator projection for their map images [8] called Web Mercator or Google Web Mercator. More on Equidistance Projections Equidistant map projections make the distance from the centre of the projection to any other place on the map uniform in all directions.

In accomplishing this, the unavoidable east-west stretching of the map, which increases as distance away from the equator increases, is accompanied in the Mercator projection by a corresponding north-south stretching, so that at every point location the east-west scale is the same as the north-south scale, making it a conformal map projection.

The figure above is a count of the census tracts that intersect the km buffer zones of each of the two projections, Web Mercator and USA Contiguous Equidistant Conic. If these sheets were brought to the same scale and assembled an approximation of the Mercator projection would be obtained Projections that minimize distortions in… …shape are called conformal projections.

Arno Peters stirred controversy when he proposed what is now usually called the Gall—Peters projection as the alternative to the Mercator. The Equidistant Conic buffer zones in the Web Mercator map above more accurately define a km buffer zone around each location than those generated using the Web Mercator projection.

Use a conformal projection when the main purpose of the large-scale map involves: Africa also appears to be roughly the same size as Europewhen in reality Africa is nearly 3 times larger.

Take note that no map projection can preserve shapes for large regions and as such, conformal projections are usually employed for large-scale mapping applications 1: The cylinder is then unrolled to give the planar map. Local angles on the sphere are mapped to the same angles in the projection, therefore graticule lines intersect at degree angles.

For small elements, the angle PKQ is approximately a right angle and therefore tan.

Mercator projection

We know from the Tissot Indicatrix that circles become enlarged as we move away from the equator but yet the distance of the buffers remains constant as we move from south to north. Two main problems prevented its immediate application: The projection he promoted is a specific parameterization of the cylindrical equal-area projection.

Since the cylinder is tangential to the globe at the equator, the scale factor between globe and cylinder is unity on the equator but nowhere else. As in all cylindrical projectionsparallels and meridians are straight and perpendicular to each other. To fit the contiguous United Stated on to an A0 poster you need a scale of around 1: The Mercator projection is still commonly used for areas near the equator, however, where distortion is minimal.

The rectangular nature results in all parallels having the same length and all meridians having the same length. If Area is important to the underlying data being visualised for the United States, then this is one of the projections you should be using to display your data.

This is false, but why is this? The simplest include a the equatorial Web mercator projection of the ellipsoid, b the arithmetic or geometric mean of the semi-axes of the ellipsoid, c the radius of the sphere having the same volume as the ellipsoid.

The projection should minimalise distortions for your area of interest, but more importantly, if your map requires that a particular spatial property shape, area, direction, or distance to be held true, then the projection you choose must preserve that property.

So this tells us that the km buffer generated in the Web Mercator projection around Bar Harbor the most northerly location on the map covers far less an area than the same buffer zone generated for Miami Beach the most southerly location.

The choice of projected coordinate system you choose really boils down to two aspects. Although the method of construction is not explained by the author, Mercator probably used a graphical method, transferring some rhumb lines previously plotted on a globe to a square graticule grid formed by lines of latitude and longitudeand then adjusting the spacing between parallels so that those lines became straight, making the same angle with the meridians as in the globe.

Similarly, if you need to preserve the area of features, such as land parcels for analysis and visual display you might consider an equal-area projection like the USA Contiguous Albers Equal Area Conic projection.

According to Kenneth Field a. More on Conformal Projections Conformal projections preserve local shape and angles i. Projections are not important when people are only interested in the relative location of features on a map.

We know that this projection EPSG: If you are paying a vendor for their services make sure that their applications are providing you with accurate data analysis for better decision making. German Erhard Etzlaub c. As we move away from the equator these buffer zones are going to become enlarged as shown in the figure below.systems, Web Mercator has become the dominant projection.

While the Mercator projection has a long history of discus- sion about its inappropriateness for general-purpose mapping, particularly at the global scale, and seems to have been. Most maps that we see on the web use the Web Mercator projection.

Web Mercator gained its popularity because it provides an efficient way for a two-dimen. Be aware that this projection is widely considered inappropriate for many kinds of thematic mapping for anything larger than local areas, so be careful, and avoid Mercator outside those web environments.

Web Mercator Projection & Raster Tile Maps Two cornerstones of Online Map Service Providers Emmanuel Stefanakis Dept. of Geodesy & Geomatics Engineering. Web Mercator is a map projection commonly implemented in commercial and open source data sets and internet based visualization applications. The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in Web Mercator.

Many major online street mapping services (Bing Maps, OpenStreetMap, Google Maps, MapQuest, Yahoo! Maps, and others) use a.

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Web mercator projection
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