GeoGridLines

is an option for GeoGraphics that specifies what parallels and meridians to show.

Details

The following settings can be given for GeoGridLines:

	None	no geo grid lines drawn
	Automatic	geo grid lines placed automatically
	n	approximate number of parallels and meridians
	Quantity[…]	geo grid lines placed at multiples of an angular quantity
	{latgrid,longrid}	geo grid lines specified separately for latitude and longitude

With the Automatic setting, geo grid lines are usually placed at points whose coordinates have the minimum number of digits in their decimal representation.
For each latitude/longitude coordinate, the following grid line options can be given:

	None	no geo grid lines drawn
	Automatic	geo grid line positions chosen automatically
	n	approximate number of parallels and meridians
	Quantity[…]	geo grid lines placed at multiples of an angular quantity
	{x₁,x₂,…}	geo grid lines drawn at the specified positions
	{{x₁,style₁},…}	geo grid lines with specified styles
	func	function to be applied to x_min, x_max to get geo grid line option

When a positive integer n is specified for either latitude or longitude, various heuristics are applied to produce "nice" geo grid lines. As a result, the number of grid lines actually shown may not be exactly n.
For GeoGridLines->n or GeoGridLines->Automatic, the number of grid lines shown may differ between parallels and meridians.
For a Quantity specification, only angular quantities are supported.
The geo grid line function func[x_min,x_max] may return any other geo grid line option.
AbsoluteOptions can be used to extract explicit lists of latitudes and longitudes that were used for GeoGridLines specifications given Automatic settings.
Use GeoGridLinesStyle to set styles for geo grid lines.

Examples

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Basic Examples (3)

Overlay a map with geo grid lines using default styling:

Use the Albers projection:

Draw geo grid lines at specific lines of latitude and longitude:

Specify geo grid styles:

Scope (8)

GeoGridLines Positions (5)

Place the geo grid lines automatically:

Draw geo grid lines at specific lines of latitude:

Draw geo grid lines at specific lines of longitude:

Draw geo grid lines at specific lines of latitude and longitude:

Specify the target number of geo grid lines:

Specify different numbers of latitude and longitude geo grid lines:

Draw geo grid lines as multiples of a given angle:

GeoGridLines Styling (3)

Specify the style of each geo grid line:

Specify overall geo grid line style using GeoGridLinesStyle:

Individually styled geo grid lines can be used with GeoGridLinesStyle and have higher priority:

Generalizations & Extensions (1)

Specify a grid function applied to x_min and x_max values of each direction:

Applications (2)

Plot a solid line at multiples of 30° and a dashed line at multiples of 10°:

Show geo grid lines on the Bonne projection:

Properties & Relations (2)

Geo grid lines are always drawn above the graphics:

Use AbsoluteOptions to get the grid lines used with an Automatic setting:

Possible Issues (4)

Specifying GeoGridLinesStyle in addition to a GeoGridLines style may give a different result:

Geo grid lines may be specified as an angular quantity:

Geo grid lines may not be specified as a distance quantity:

Integer arguments and option settings for several geo functions are interpreted as distances (or radii) in meters:

However, an integer geo grid line specification indicates an approximate number of "nice" grid lines to display:

Use GeoPath to interactively display geo coordinates of geo lines:

Neat Examples (3)

A random collection of geo grid lines:

Use geo grid lines with 1° graticule over Australia:

Plot geo grid lines at positions of the largest US cities:

Compute their coordinates:

Display a map of the US with lines of latitude and longitude passing through the largest cities:

Introduced in 2014

(10.0)

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