Julia interface functions

Geodesic(a, f) -> geodesic

Set up an ellipsoid for geodesic calculations. a is the semimajor radius of the ellipsoid, whilst flattening is given by f.

GeodesicLine([ellipsoid::Geodesic.WGS84,] lon1, lat1; azi, lon2, lat2, angle, dist)

Construct a GeodesicLine, which may be used to efficiently compute many distances along a great circle. Set the coordinates of the starting point lon1° and lat1°. There are two ways to define the great circle this way:

1. Set a start point, azimuth, and optionally distance. This requires the keyword arguments azi1 (all °) and optionally either angle (angular distance, °) or distance dist (m).
2. Set a start point and end point. This requires the keyword arguments lon2 and lat2 (all °).

If ellipsoid is not supplied, then WGS84 is used by default.

See forward and forward_deg for details of computing points along a GeodesicLine.

Polygon([ellipsoid::Geodesic=WGS84,] polyline=false)

Construct a Polygon, which contains a set of points on a certain ellipsoid.

With this construction, the Polygon contains no points.

If polyline is true, then the Polygon will not accumulate area and instead only its perimeter can be calculated.

Polygon([ellipsoid::Geodesic=WGS84,] lons, lat) -> polygon

Construct a polygon from arrays of coordinates lons and lats, optionally specifying an ellipsoid, which defaults to WGS84.

Calculate the polygon's area and perimeter with properties.

forward([ellipsoid::Geodesic=WGS84,] lon, lat, azi, dist) -> lon′, lat′, baz, dist, angle

Compute the final position when travelling from longitude lon°, latitude lat°, along an azimuth of azi° for dist m (or whichever units the ellipsoid is defined using). The final coordinates are (lon′, lat′)°, the backazimuth from the final point to the start is baz°, and the angular distance is angle°.

If ellipsoid is not supplied, then WGS84 is used by default.

forward(a, f, lon, lat, azi, dist) -> lon′, lat′, baz, dist, angle

Compute the final point assuming an ellipsoid with semimajor axis a m and flattening f.

Note that precomputing the ellipsoid with Geodesic and then reusing this if multiple forward or forward_deg calculations are needed will be more efficient.

forward(line::GeodesicLine, dist) -> lon′, lat′, baz, dist, angle

Compute the final point when travelling along a pre-computed great circle line for a distance of dist m. angle is the angular distance in °.

forward_deg([ellipsoid::Geodesic=WGS84,] lon, lat, azi, angle) -> lon′, lat′, baz, dist, angle

Compute the final position when travelling from longitude lon°, latitude lat°, along an azimuth of azi° for an angular distance of angle°. The final coordinates are (lon′, lat′)°, the backazimuth from the final point to the start is baz°, and the distance is dist m.

If ellipsoid is not supplied, then WGS84 is used by default.

forward_deg(a, f, lon, lat, azi, angle) -> lon′, lat′, baz, dist, angle

Compute the final point assuming an ellipsoid with semimajor radius a m and flattening f.

Note that precomputing the ellipsoid with Geodesic and then reusing this if multiple forward_deg calculations are needed will be more efficient.

forward_deg(line::GeodesicLine, angle) -> lon, lat, baz, dist

Compute the final point when travelling along a pre-computed great circle line for an angular distance of angle °. dist is the distance in m.

inverse([ellipsoid::Geodesic=WGS84,] lon1, lat1, lon2, lat2) -> azi, baz, dist, angle

Compute for forward azimuth azi°, backazimuth baz°, surface distance dist m and angular distance angle° when travelling from (lon1, lat1)° to a second point (lon2, lat2)°.

If ellipsoid is not supplied, then WGS84 is used by default.

inverse(a, f, lon1, lat1, lon2, lat2) -> azi, baz, dist, angle

Compute the final point assuming an ellipsoid with semimajor radius a m and flattening f.

Note that precomputing the ellipsoid with Geodesic(a, f) and then reusing this if multiple inverse calculations are needed will be more efficient.

waypoints(line::GeodesicLine; n, dist, angle) -> points

Return a set of points along a great circle line (which must have been specified with a distance or as between two points). There are three options:

• Specify n, the number of points (including the endpoints)
• Specift dist, the distance between each point in m
• Specify angle, the angular distance between each point in °.

In all cases, the start and end points are always included. When giving either dist or angle, the penultimate point may not be respectively dist m or angle° away from the final point.

The output is a vector of named tuples as returned by forward or forward_deg.

add_point!(polygon, lon, lat) -> polygon

Add a point to a geodesic polygon in order to later compute its perimeter and area with properties.

add_edge!(polygon, azi, dist) -> polygon

Add a point to a polygon by specifying the azimuth azi (°) and distance dist (m) from the previous point, in order to later compute its perimeter and area with properties.

properties(polygon::Polygon) -> npoints, perimeter, area

Return the number of points npoints, perimeter (m) and area (m²) of the geodesic polygon.

Ellipsoid of the WGS84 system, with a semimajor radius of 6.378137e6 m and flattening 0.0033528106647474805.