About interval and layer values in export files

Time/distance units

Start interval numbers at the start of the echogram option on the Grid page

Numbering system in export file or on screen

Time

Available

Select Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use relative interrval numbering. At the start of the echogram and the left most interval is numbered 1.

Clear Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use absolute interval numbering with respect to the start of the fileset. The left-most interval of the first raw variable is numbered 1. The intervals of the selected variable are numbered according to the number of time intervals, equal in length to the value entered in the Time between grid lines (minutes) box, that have passed since 1/1/1970.

GPS Distance (nmi)

Available

Select Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use relative interrval numbering. The left-most interval of the echogram is numbered 1.

Clear Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use absolute interval numbering. Intervals are numbered from the the first GPS fix with interval increments equal in size to the Distance between grid lines value.

Vessel log distance (nmi)

Available

Select Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use relative interrval numbering. The left most interval is numbered 0.

Clear Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use absolute interval numbering. Intervals are numbered from the first Vessel log with interval increments equal in size to the Distance between grid lines value.

GPS Distance (m)

Available

Select Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use relative interrval numbering. The left-most interval of the echogram is numbered 1.

Clear Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use absolute interval numbering. Intervals are numbered from the the first GPS fix with interval increments equal in size to the Distance between grid lines value.

Vessel log distance (m)

Available

Select Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use relative interrval numbering. The left most interval is numbered 0.

Clear Start interval numbers at the start of the echogram on the Grid page of Variable Properties dialog box, to use absolute interval numbering. Intervals are numbered from the first Vessel log with interval increments equal in size to the Distance between grid lines value.

Depth/range/Line-referenced units

Echogram mode

Numbering system in export file
 

Surface (depth of zero)
 

Depth

Measured from Surface (depth of zero), nominally the water surface. The first layer (from the water surface to the first grid line) is layer 1. Where data exists above the water surface the first layer above the water surface is layer 0 and subsequent layers are numbered negatively (-1, -2, -3 ...).

Tranducer face (range of zero)

Range

Measured from Transducer face (range of zero). The first layer (from the transducer face to the first grid line) is layer 1. Layer numbers below the transducer are positive, layer numbers above the transducer are negative.

Line-reference

Depth or Range

Measured from a selected line in the EV file. The first layer above the Line-reference is layer 0. Layers above the first layer are negative. Layers below the Line-reference are positive.