mt_azimuth: Calculate azimuths or turn angles

In move2: Processing and Analysing Animal Trajectories

Calculate azimuths or turn angles

Description

• mt_azimuth: calculates the heading/azimuth/direction of movement of each segment between consecutive locations of a track.

• mt_turnangle: calculates the relative angle between consecutive segments.

Usage

mt_azimuth(x, units)

mt_turnangle(x, units)

Arguments

x	a move2 object. Timestamps must be ordered within tracks and only contain location data and it must be in a geographic coordinate system or without a coordinate reference system (See 'Details').
units	Optional. Valid values are character, symbolic_units or units, for more details see the value argument of units::as_units. If no units are stated (default) the function flexibly determines the units to return. Fixing the units can be useful if specific return units are for example required for subsequent functions. This argument only takes effect if the initial return value already has units.

Details

mt_is_time_ordered_non_empty_points can be used to check if the timestamps are ordered and if the object only contains location data. To omit empty locations use e.g. dplyr::filter(x,!sf::st_is_empty(x)).

Currently the calculation of both angles is only implemented for data in a geographic coordinate system and data without coordinates reference system. To reproject the data into long/lat use e.g. sf::st_transform(x, crs="EPSG:4326")

Azimuths for geographic coordinates are calculated using lwgeom::st_geod_azimuth(). The angles are relative to the North pole.

Value

A vector of angles, currently default is in radians (between -pi and pi).

In mt_azimuth north is represented by 0, positive values are movements towards the east, and negative values towards the west. The last value for each track will be NA.

In mt_turnangle negative values are left turns and positive right turns. The first and the last value for each track will be NA.

See Also

Other track-measures: mt_distance(), mt_time()

Examples

data <- mt_sim_brownian_motion()
mt_azimuth(data)
mt_turnangle(data)

x <- mt_read(mt_example())[330:340, ]
mt_azimuth(x)
mt_turnangle(x)

move2 documentation built on April 4, 2025, 12:24 a.m.