Elevation Mode and RTK Tides in the Single Beam Editor
Recently, we had an situation where one of our users was using RTK
(Real Time Kinematic) tide corrections while processing their survey
data in elevation mode. When the data was read into the Single Beam
Editor, the calculations were incorrect.
With closer examination of the measurements and the calculations that
occur, we determined that when you convert single beam data to
elevation mode and are using RTK tide corrections, an additional
adjustment is required. The tide correction value must be negated.
Let's take a closer look.
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Most surveys are done in Depth Mode where the sounding depths are positive values. In Hypack® Max, the tide correction value is added to the sounding depth to remove the effects of the change in tide. Since we want to remove this amount from the sounding depths, the value must be negative. [C = A + (-B)]
For example:
Where A = 30, B = 5, C = 25, the equation becomes 25 = 30 + (-5).
In Elevation Mode, the sounding depths are negative. The tide corrections, therefore, must be positive. Using the example above, the equation becomes -25 = -30 + 5.
For Single Beam surveys:
- Convert the Depths to Elevation Mode by selecting Depths--Invert Only in the Read Parameters dialog.
- Convert the tide correction from negative to positive by checking the Invert Tide Values box in the Advanced Read Parameters dialog in the Single Beam Editor.
For Multibeam surveys all corrections are automatically adjusted by the Hysweep Editor without further action by you.
