Coordinate transformations

There are two types of coordinate transformations available, for 4-beam ADCP's in a convex Janus configuration or 5-beam ADCP's (four Janus beams plus one vertical beam):

• Beam coordinates to Earth coordinates (janus2earth.m and janus5beam2earth.m).
• Beam coordinates to instrument coordinates (janus2xyz.m and janus5beam2xyz.m).

The beam-to-Earth coordinate transformation codes call their respective beam-to-instrument transformation codes.

Beam-to-instrument transformation

By assuming spatial homogeneity of the velocity field between beams, the geometry of a 5-beam Janus ADCP's transducers gives the following linear transformation from beam- to instrument (xyz)-coordinates:

where the xyz coordinate system is defined as follows (TRDI's convention):

x-axis: Increases in beam 1's direction, away from instrument.

y-axis: Increases in beam 3's direction, away from instrument.

z-axis: Increases in beam 5's direction, away from instrument.