lookangles

Satellite look angles from receiver and satellite positions

Description

[az,el,vis] = lookangles(recPos,satPos) returns the look angles and visibilities of satellite positions for a given receiver position. The azimuth az and elevation el are the look angles in degrees in the Earth-centered Earth-fixed (ECEF) coordinate system. The visibility of the satellites vis is a logical array that the function calculates using the default receiver mask angle of 10 degrees.

example

[az,el,vis] = lookangles(recPos,satPos,maskAngle) returns the look angles and visibilities of satellites with a specified mask angle maskAngle in degrees.

Examples

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Use the lookangles function to get the azimuth and elevation angles of satellites for given satellite and receiver positions. Specify a mask angle of 5 degrees. Get the satellite positions using the gnssconstellation function.

Specify a receiver position in geodetic coordinates (latitude, longitude, altitude).

recPos = [42 -71 50];

Get the satellite positions for the current time.

t = datetime('now');
gpsSatPos = gnssconstellation(t);

Specify a mask angle of 5 degrees.

Get the azimuth and elevation look angles for the satellite positions. The vis output indicates which satellites are visible. Get the total using nnz.

fprintf('%d satellites visible at %s.\n',nnz(vis),t);
8 satellites visible at 23-Oct-2021 11:12:39.

Input Arguments

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Receiver position in geodetic coordinates, specified as a three-element vector of the form [latitude longitude altitude]

Data Types: single | double

Satellite positions in the Earth-centered Earth-fixed (ECEF) coordinate system in meters, specified as an N-by-3 matrix of scalars. N is the number of satellites in the constellation.

Data Types: single | double

Elevation mask angle of the receiver, specified as a positive scalar in degrees.

Data Types: single | double

Output Arguments

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Azimuth angles for visible satellite positions, returned as an n-element vector of angles. n is the number of visible satellite positions in the plot. Azimuth angles are measured in degrees, clockwise-positive from the north direction looking down.

Example: [25 45 182 356]

Data Types: double

Elevation angles for visible satellite positions, returned as an n-element vector of angles. n is the number of visible satellite positions in the plot. Elevation angles are measured from the horizon line with 90 degrees being directly up.

Example: [45 90 27 74]

Data Types: double

Satellite visibility, returned as an n-element logical array. Each element indicates whether the satellite position given by az and el is visible.

Data Types: logical