# Does the AquaPro HR measure velocities in separate cells along the vertical profile or along the beams?

FollowThe measurement cells are composed in a similar way for the HR as for the regular Aquadopp Profile. Confer the Principles of Operation for a schematic drawing.

The cell position are composes by a transmit pulse that has the same length as the receive window. The convolution of the two is a triangular weighting function that makes up for the individual cells. The cell position is referred to the peak in the triangular weighting function. This means that the position (Zi) of an arbitrary cell mid-point is given by:

Zi = Blanking + i × Cell size

The base line of each cell is equal to twice the distance between adjacent cells, whereas the distance between adjacent mid-point equals the cell size you set in the configuration. From this it follows that there is a 50% overlap between adjacent cells as you can see in the already mentioned manual.

In all current profilers, the velocity is measured in fixed cells along each acoustic beam. The length of each cell ("cell size") is projected onto the vertical axis. So if we speak of a cell of 1 m, this refers to the projection along the vertical axis.

For example: 0.2m blanking distance and a cell size of 0.1m the position of the first cell is 0.3m from the sensor head. The corresponding length of the cell along the acoustic beam is 1/cos 25.

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