.cutDive(x, descent.crit.q, ascent.crit.q, wiggle.tol).diveIndices(diveID, diveNo)
.getInterval(time).getSpeedStats(x, vdist).cutDive: a 2-col
matrix with subscript in original TDR object and non NA depths. For
.descAsc: a 4-col matrix with dive id, time, depth, and
speed. For .getSpeedStats: a 3-coPOSIXct object representing time.diveID..getSpeedCalib extracts the rates of descent and ascent with associated mean speed during descent and ascent phases, respectively and returns a list that is later manipulated by doSpeedCalib to calibrate speed. The speed used for each rate of depth change corresponds to the speed read for the last point, assuming that each speed reading is the average speed for the last measurement interval.