# Geometry

group harp_geometry

The HARP Geometry module contains public functions for dealing with polygons and points on a spherical surface.

Functions

int harp_geometry_get_point_distance(double latitude_a, double longitude_a, double latitude_b, double longitude_b, double *distance)

Calculate the distance between two points on the surface of the Earth in meters

This function assumes a spherical earth

Return

• 0, Success.

• -1, Error occurred (check harp_errno).

Parameters
• latitude_a: Latitude of first point

• longitude_a: Longitude of first point

• latitude_b: Latitude of second point

• longitude_b: Longitude of second point

• distance: Pointer to the C variable where the surface distance in [m] between the two points will be stored.

int harp_geometry_has_point_in_area(double latitude_point, double longitude_point, int num_vertices, double *latitude_bounds, double *longitude_bounds, int *in_area)

Determine whether a point is in an area on the surface of the Earth

This function assumes a spherical earth.

The latitude/longitude bounds can be either vertices of a polygon (num_vertices>=3) or represent corner points that define a bounding rect (num_vertices==2).

Return

• 0, Success.

• -1, Error occurred (check harp_errno).

Parameters
• latitude_point: Latitude of the point

• longitude_point: Longitude of the point

• num_vertices: The number of vertices of the bounding polygon/rect of the area

• latitude_bounds: Latitude values of the bounds of the area polygon/rect

• longitude_bounds: Longitude values of the bounds of the area polygon/rect

• in_area: Pointer to the C variable where the result will be stored (1 if point is in the area, 0 otherwise).

int harp_geometry_has_area_overlap(int num_vertices_a, double *latitude_bounds_a, double *longitude_bounds_a, int num_vertices_b, double *latitude_bounds_b, double *longitude_bounds_b, int *has_overlap, double *fraction)

Determine the amount of overlap of two areas on the surface of the Earth

This function assumes a spherical earth. The overlap fraction is calculated as area(intersection)/min(area(A),area(B)).

The latitude/longitude bounds for A and B can be either vertices of a polygon (num_vertices>=3), or represent corner points that define a bounding rect (num_vertices==2).

Return

• 0, Success.

• -1, Error occurred (check harp_errno).

Parameters
• num_vertices_a: The number of vertices of the bounding polygon/rect of the first area

• latitude_bounds_a: Latitude values of the bounds of the area of the first polygon/rect

• longitude_bounds_a: Longitude values of the bounds of the area of the first polygon/rect

• num_vertices_b: The number of vertices of the bounding polygon/rect of the second area

• latitude_bounds_b: Latitude values of the bounds of the area of the second polygon/rect

• longitude_bounds_b: Longitude values of the bounds of the area of the second polygon/rect

• has_overlap: Pointer to the C variable where the result will be stored (1 if there is overlap, 0 otherwise).

• fraction: Pointer to the C variable where the overlap fraction will be stored (use NULL if not needed).

int harp_geometry_get_area(int num_vertices, double *latitude_bounds, double *longitude_bounds, double *area)

Calculate the area size for a polygon on the surface of the Earth

This function assumes a spherical earth.

The latitude/longitude bounds for A and B can be either vertices of a polygon (num_vertices>=3), or represent corner points that define a bounding rect (num_vertices==2).

Return

• 0, Success.

• -1, Error occurred (check harp_errno).

Parameters
• num_vertices: The number of vertices of the bounding polygon/rect

• latitude_bounds: Latitude values of the bounds of the polygon/rect

• longitude_bounds: Longitude values of the bounds of the polygon/rect

• area: Pointer to the C variable where the area size will be stored (in [m2]).