envelope v0.3.0 Envelope

A library for calculating envelopes of geometries and tools to compare them. This is most useful as an approximation of spacial relationships between more complicated geometries.

iex> Envelope.from_geo( %Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]} )
%Envelope{ min_x: 2, min_y: -2, max_x: 20, max_y: 11 }

iex> Envelope.from_geo( %Geo.LineString{coordinates: [{1, 3}, {2, -1}, {0, -1}, {1, 3}]} )
%Envelope{ min_x: 0, min_y: -1, max_x: 2, max_y: 3 }

You can also expand an existing Envelope with a geometry or another Envelope

iex> a = Envelope.from_geo( %Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]} )
...> b = %Geo.LineString{coordinates: [{1, 3}, {2, -1}, {0, -1}, {1, 3}]}
...> Envelope.expand(a, b)
%Envelope{ min_x: 0, min_y: -2, max_x: 20, max_y: 11 }

Summary

Functions

Calculates the simple area of an Envelope

Estimates the area of an Envelope in square meters when the Envelope’s coordinates are in degress of longitude and latitude

Returns whether one envelope fully contains another envelope or point

Returns an Envelope that represents no extent at all. This is primarily a convenience function for starting an expanding Envelope. Internally, “empty” Envelopes are represented with nil values for all extents

Returns true if the given envelope is empty (has non-existent extent), otherwise false

Returns a new Envelope that is expanded to include an additional geometry

Returns a new Envelope that is expanded in positive and negative directions in each axis by radius

Returns an Envelope that represents the extent of the geometry or coordinates

Simple distance from the bottom bounadary to the top boundary of the Envelope

When an Envelope’s coordinates are in degress of longitude and latitude, calculates the great circle distance between the center of the north and south extent in meters

Returns whether two envelopes touch or intersect

Simple distance from the left bounadary to the right boundary of the Envelope

When an Envelope’s coordinates are in degress of longitude and latitude, calculates the great circle distance between the center of the east and west extent in meters

Types

points ::
  {number, number} |
  list |
  %{coordinates: list} |
  %Geo.Point{coordinates: term, srid: term} |
  %Geo.MultiPoint{coordinates: term, srid: term} |
  %Geo.LineString{coordinates: term, srid: term} |
  %Geo.MultiLineString{coordinates: term, srid: term} |
  %Geo.Polygon{coordinates: term, srid: term} |
  %Geo.MultiPolygon{coordinates: term, srid: term}

Functions

area(env)

Specs

area(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

Calculates the simple area of an Envelope.

Examples

iex> Envelope.area(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]}))
234
area_gc(env)

Specs

area_gc(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

Estimates the area of an Envelope in square meters when the Envelope’s coordinates are in degress of longitude and latitude.

Examples

iex> Envelope.area_gc(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]})) |> round
2865575088701
contains?(env, env2)

Specs

contains?(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}, %Envelope{max_x: term, max_y: term, min_x: term, min_y: term} | {number, number}) :: boolean

Returns whether one envelope fully contains another envelope or point.

Examples

iex> Envelope.contains?(
...> %Envelope{ min_x: -1, min_y: -5, max_x: 23, max_y: 14 },
...> %Envelope{ min_x: 0, min_y: 3, max_x: 7, max_y: 4 })
true

iex> Envelope.contains?(
...> %Envelope{ min_x: -1, min_y: 5, max_x: 23, max_y: 14 },
...> %Envelope{ min_x: 0, min_y: 5, max_x: 7, max_y: 4 })
true

iex> Envelope.contains?(
...> %Envelope{ min_x: -1, min_y: 5, max_x: 23, max_y: 14 },
...> {0, 11})
true
empty()

Specs

empty :: %Envelope{max_x: term, max_y: term, min_x: term, min_y: term}

Returns an Envelope that represents no extent at all. This is primarily a convenience function for starting an expanding Envelope. Internally, “empty” Envelopes are represented with nil values for all extents.

Note that there is a important distinction between an empty Envelope and an Envelope around a single Point (where the min and max for each axis are real numbers but may represent zero area).

Examples

iex> Envelope.empty
%Envelope{max_x: nil, max_y: nil, min_x: nil, min_y: nil}

iex> Envelope.empty |> Envelope.empty?
true
empty?(envelope)

Specs

empty?(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: boolean

Returns true if the given envelope is empty (has non-existent extent), otherwise false

Examples

iex> Envelope.empty |> Envelope.empty?
true

iex> %Envelope{ min_x: 0, min_y: -1, max_x: 2, max_y: 3 } |> Envelope.empty?
false
expand(env1, env2)

Specs

expand(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}, {number, number} | %Envelope{max_x: term, max_y: term, min_x: term, min_y: term} | points) :: %Envelope{max_x: term, max_y: term, min_x: term, min_y: term}

Returns a new Envelope that is expanded to include an additional geometry.

Examples

iex> a = Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]})
...> b = %Geo.LineString{coordinates: [{1, 3}, {2, -1}, {0, -1}, {1, 3}]}
...> Envelope.expand(a, b)
%Envelope{ min_x: 0, min_y: -2, max_x: 20, max_y: 11 }

iex> a = %Envelope{ min_x: 0, min_y: -2, max_x: 20, max_y: 11 }
...> b = %Envelope{ min_x: 2, min_y: -3, max_x: 12, max_y: -2 }
...> Envelope.expand(a, b)
%Envelope{ min_x: 0, min_y: -3, max_x: 20, max_y: 11 }

iex> Envelope.expand(Envelope.empty, %Envelope{ min_x: 0, min_y: -2, max_x: 20, max_y: 11 })
%Envelope{ min_x: 0, min_y: -2, max_x: 20, max_y: 11 }

iex> Envelope.expand(Envelope.empty, Envelope.empty) |> Envelope.empty?
true
expand_by(env, radius)

Specs

expand_by(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}, number) :: %Envelope{max_x: term, max_y: term, min_x: term, min_y: term}

Returns a new Envelope that is expanded in positive and negative directions in each axis by radius.

Examples

iex> Envelope.expand_by(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]}), 3)
%Envelope{ min_x: -1, min_y: -5, max_x: 23, max_y: 14 }

iex> Envelope.expand_by(Envelope.empty, 4) |> Envelope.empty?
true
from_geo(coordinates)

Specs

from_geo(points) :: %Envelope{max_x: term, max_y: term, min_x: term, min_y: term}

Returns an Envelope that represents the extent of the geometry or coordinates.

Examples

iex> Envelope.from_geo %{coordinates: [{11, 10}, {4, 2.5}, {16, 2.5}, {11, 10}]}
%Envelope{ max_x: 16, max_y: 10, min_x: 4, min_y: 2.5 }

iex> Envelope.from_geo [{11, 10}, {4, 2.5}, {16, 2.5}, {11, 10}]
%Envelope{ max_x: 16, max_y: 10, min_x: 4, min_y: 2.5 }

iex> Envelope.from_geo %Geo.Polygon{coordinates: [[{1, 3}, {2, -1}, {0, -1}, {1, 3}]]}
%Envelope{ min_x: 0, min_y: -1, max_x: 2, max_y: 3 }

iex> Envelope.from_geo {1, 3}
%Envelope{ min_x: 1, min_y: 3, max_x: 1, max_y: 3 }
height(env)

Specs

height(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

Simple distance from the bottom bounadary to the top boundary of the Envelope.

Examples

iex> Envelope.height(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]}))
13
height_gc(env)

Specs

height_gc(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

When an Envelope’s coordinates are in degress of longitude and latitude, calculates the great circle distance between the center of the north and south extent in meters.

Examples

iex> Envelope.height_gc(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]})) |> round
1445536
intersects?(env1, env2)

Specs

intersects?(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}, %Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: boolean

Returns whether two envelopes touch or intersect.

Examples

iex> Envelope.intersects?(
...> %Envelope{ min_x: -1, min_y: -5, max_x: 23, max_y: 14 },
...> %Envelope{ min_x: 0, min_y: 3, max_x: 7, max_y: 4 })
true

iex> Envelope.intersects?(
...> %Envelope{ min_x: -1, min_y: 5, max_x: 23, max_y: 14 },
...> %Envelope{ min_x: 0, min_y: -3, max_x: 7, max_y: 4 })
false
width(env)

Specs

width(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

Simple distance from the left bounadary to the right boundary of the Envelope.

Examples

iex> Envelope.width(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]}))
18
width_gc(env)

Specs

width_gc(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}) :: number

When an Envelope’s coordinates are in degress of longitude and latitude, calculates the great circle distance between the center of the east and west extent in meters.

Examples

iex> Envelope.width_gc(Envelope.from_geo(%Geo.Polygon{coordinates: [[{2, -2}, {20, -2}, {11, 11}, {2, -2}]]})) |> round
1982362
within?(a, b)

Specs

within?(%Envelope{max_x: term, max_y: term, min_x: term, min_y: term}, %Envelope{max_x: term, max_y: term, min_x: term, min_y: term} | {number, number}) :: boolean