Latitude / Longitude Projection

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Not really a projection, but the graphical figure obtained by plotting latitude and longitude degree coordinates as if they were Y and X coordinates. It is also known as the geographical projection.

 

Note that one latitude / longitude projection may be different from another because each such projection assumes that a particular datum is in use. While the WGS84 datum is almost universally assumed to the datum used, it is possible that some person assumed a different datum.

 

It is also possible to re-project latitude / longitude data into different datums, even including datums that include rotation factors. In such cases Manifold will faithfully re-project the data as direct taking into account datum rotation factors if applicable.

 

Scale

 

True in degrees along the Equator or vertically along any meridian.

 

Distortion

 

Considerable distortion away from the Equator due to horizontal increase in longitude degrees.

 

Usage

 

Used to save digital maps in "unprojected" form using some assumed datum.  

 

Latitude / Longitude is characteristic of older GIS products, but it is a really awful projection to use for most GIS work, primarily because the units of measure are radial units, degrees, and not linear units like feet or meters.  

 

The length of a "degree" depends on whether it is a degree of latitude or a degree of longitude with the length of a degree of longitude changing from around 110 degrees at the Equator to only a few centimeters very near the North or South Pole.   For one of the main tasks GIS is used, measurement, "degrees" are a terrible choice.