Q: When it comes to recalculate of bathy data what types of calculations and formulas does NaviEdit have and use?


A:When the bathy is recalculated in NaviEdit we have 6 different types of pressure to depth conversion formulas.



First formula, simple (depth correction):

This is the most simple case and the only case where the current depth value is reused.

The depth Z is corrected with 10 times the difference between the surface pressure and the reference 0-level pressure.

 

Second formula, simple (constant density):

The depth is corrected with the density value as follows:                       

 Z = 10*(pressure – surface pressure)\(density *gravity)b

         

Third formula, Saunders and Fofonoff:

Sounders and Fofonoff is the UNSESCO formula (see no. 4)  without integration of the geopotential anomaly:


Forth formula, UNESCO:

Is the UNESCO formula with the integration of the geopotential anomaly. This integration requires a linked CTD:

 

Fifth formula, Caspian Sea - requires a linked CTD:

This formula is using the geopotential anomaly correction as stated below where an integration over the complete water column covered by the vertical CTD is done.




Sixth formula, Caspian Sea - requires a horizontal CT (Aux Sensor):

This formula is using the Density Ratio Correction from below.



The Caspian Sea formula is:



Seventh formula, Caspian Sea - input values:

This formula is using the manual input values for the Temperature and Salinity.



Surface Pressure


Formula used:

Resulting Pressure = Observed pressure - Surface Pressure + 0 (Level Reference Pressure)  


The options that can be used:


1.Fixed: a fixed value in bars to be used for the calculation.
2. Use other "Pressure block tab'': if you have an ASCII file imported as a (barometric) pressure block please see below, then the block can be selected in the Header Editor for the file where you want to apply the pressure in the ‘Pressure to Depth’ calculation:



3. Use single beam for this block: allows to select another instrument where the surface pressure was logged. For pressure sensor types, NaviEdit will in some cases import the pressure as a bathy and in other cases as a single-beam/channel. You can choose to either use a bathy or single-beam/channel.

4. 0-Level Reference - this is for tare and needs to be entered in bars. It can be used when the tare was not set/subtracted from the instrument.