Eye4Software Hydromagic

  Hydrographic Survey Software


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Tide correction settings

The next step in the conversion process is to specify whether and how the sounding needs to be corrected for tides. We will discuss the different tide options below. When you are not in a tidal area or only depth values are required (not elevations), you can select the first option ("Do not use tide corrections"), and click the "Next" button to proceed to the sound velocity and dynamic draft corrections page.

Tide correction settings in the sounding wizard
On the third page of the wizard you can configure the tide or vertical datum settings.


Option #1 - Do not use tide corrections, do not alter depth values

When the survey data collected is not related to tidal fluctuations, and you do not have to measure against a local vertical datum such as NAVD88, you can use this option. With this option selected the soundings will copied to the sounding file(s) as they are without tide correction. In your final products you can only export depth values, not elevations.


Option #2 - Use tide gauge or manual measurements as stored in raw data file

If a tide gauge is used, you have to select the "Use tide gauge measurements" option. With this option selected, Hydromagic will use tide adjustments recorded in the raw data file (by a plugin communicating with a tide gauge). You should also use this option when you did use the "Hydromagic Manual Tide plugin" to store tide measurements during your survey.

Use the second option when the Hydromagic Manual Tide Plugin has been used
Use the second option when the "Hydromagic Manual Tide Plugin" has been used.


Option #3 - Elevation from RTK receiver or total station are orthometric heights

When calculating the tide level with RTK, Hydromagic expects the elevation data stored in the raw data file to be relative to the WGS84 ellipsoid. To convert this elevation to the local datum, a geoid model will be applied when converting the raw data into a sounding file. In some cases this is unwanted behavior:

In these cases, you must select the third option in order to prevent from the geoid model to be applied twice. When this option has been selected, the geoid model configured in Hydromagic will be ignored. When set, the antenna height will still be applied.

When using this option, you have to let the software know which elevation from NMEA0183 data sent by the RTK receiver or total station we need to use. More information about these fields can be found on the RTK Tide Corrections page.

You can have a look at the raw data files to see which of the fields contain the correct elevation value by using the data analysis window:

Use the raw data analysis window to check which data field contains the correct elevation value
Use the raw data analysis window to check which data field contains the correct elevation value.


Option #4 - Use tide correction file

When you want to use tide corrections without special hardware such as a RTK receiver or tide gauge, select this option.
It allows you to create a tide correction file where you can enter the tide observations made during the survey manually, or use the tide prediction tool to generate a tide file.

You can start the tide file editor by clicking the "Editor..." button, or just select an existing Hydromagic tide file by clicking the "Browse..." button.

Use the Tide File Editor to generate or modify a Hydromagic tide file
Use the "Tide File Editor" to generate or modify a Hydromagic tide file.


Option #5 - Use geoid model

When using a RTK receiver the tide level of the water you are surveying is calculated by using the high precision elevation data corrected by the selected geoid model and antenna height. This only works when your RTK receiver is in RTK fix mode, or when the collected position data is post-processed using PPK.

When using this setting, the geoid model and antenna height as configured in the "RTK" tab of the preferences window will be applied. These global RTK settings are also displayed on this wizard page (marked in red in the image below):

When option #5 is selected, the global RTK settings will be used
When option #5 is selected, the global RTK settings will be used.