How-to Tide

This How-to describes step by step how to apply tide both online and offline.
If it's applied online, the tidal data will be stored in the databases.
Offline it can be applied in the Processing Manager, so the QPD's will be updated with tidal information.
Finally we will explain how to apply tide to a survey that was done with RTK.

On this page:

Online

During an online session there are four options for inputting tidal information into the raw database:

  1. Input data from a tide gauge (or multiple) that transmits data to the vessel. Go to Tidegauge(s). (See below.)
  2. Use one or two manual gauges. Go to Manual tide gauge. (See below.)
  3. Use predicted tide using Admiralty Tide Table (ATT) parameters. This is named Online prediction (ATT). (See below.)
  4. Input tidal information by creating a (predicted) tidal data file. Go to Tidefile. (See below.)

In all four cases you need to define a Tide Gauge system in your Template database.
The Online prediction also requires a fixed node to be set up as described in the Drivers Manual help.
The rest of the settings will be defined online in the Computation Setup.

Database Setup

If a tide gauge, a manual tide setting or a 'predicted' tide file are going to be used during the online survey, a tide gauge must first be defined in the Database Setup:

  1. Define a new system.
  2. Select Tide Gauge as Type.
  3. Select the appropriate driver (select Manual Tide Gauge Input for manual input or for reading data from a file (not ATT)).
  4. In the parameter screen select “Add Tide” and then “Add” to create a new Fixed Node.
  5. Enter the appropriate information for the node. This node is the location of the tide gauge.
  6. Highlight the fixed node to activate it and press OK to finish the setup.
  7. Highlight the created tidal observation. Edit the slot if multiple tidal observations exist.
  8. In the Observation Parameters screen, enter values for ‘A-priori SD’, ‘Fixed C-O’, ‘Variable C-O’, ‘Scale Factor’.
    Press ‘Apply’ to activate the changes.
  9. Click on Finish to finalize the setup.
  10. Repeat these steps if multiple tide gauges are used.

Use of one or multiple tide gauge(s)

When only one tide gauge is added as a system to the database, there is no need to enter the coordinates and height of the node.
When multiple tide gauges are used, the coordinates are important, because then the tidal value is determined based upon a weighted distance from the gauges.

Drivers and Interfacing Manual

See for more information about the different tide gauge drivers the Drivers and Interfacing Manual Tide Gauge.
Each driver has a description on how to create its used tide gauge and how to read its data in the Controller.

Computation Setup

Applying or Storing tide

Tide will only be applied, if the height status of the used positioning system is set to Unreliable in the Computation Setup (e.g. for DGPS).
Tide will not be applied if the height status is set to Accurate (e.g. RTK DGPS), however the tidal information will be stored in the database.
This storage file will only be available when a tide system was added to Database Setup.
More information on Height settings can be found in the Knowledge Base document 'How-to Height - Tide and RTK'.

  1. In the Controller, open the Computation Setup from the Settings menu.
  2. Select the object from the tree and click on the “Height” tab.

Tide gauge(s)

  1. Set the Tide method to Tide gauge or to Tide gauge (auto select)
  2. Set the number of gauges to use
  3. Set the Maximum age of the tide values
  4. Select which tide gauges should be used

Maximum number of tide gauges

A maximum of two gauges or files can be used for the online computation of the tide.
If more gauges are needed then the Tidal Processor in the Processing Manager should be used instead of the online option.

Weighted values

When the Tide gauge method is used with two tide gauges the tidal value is determined based upon a weighted distance from the gauges in the area between the two tide gauges.
When outside this area only one tide gauge will be used.

Gauges at fixed positions/nodes

When tide gauges or tide files are used it is necessary to have fixed nodes defined in the Database Setup.
The fixed nodes give the positions of the gauges and the correct height reference system to be used.

Auto select

When Tide gauge (auto select) is used, the Controller will select the two nearest stations automatically. This is based on KP values along a route and the current vessel position.

The route containing the tidal stations along, for example, a river axis should be selected as first Additional Mainline in the Session Setup.
When no additional mainline is selected, automatically the mainline will be used. Leave the fields Tide Gauge empty.
The nearest stations are automatically selected whilst online. If only one station is selected, the nearest is searched for every 60 seconds.

Display tide gauge info

Use the Generic Display to display the Tide results such as Closest Gauge and Second Gauge used.

Manual tide gauge

  1. Set the Tide method to Tide gauge
  2. Set the number of gauges to use
  3. Select which tide gauges should be used

    A manual Input driver is started when going online:

  4. Enter the value of the tide
  5. Click on Settings

  6. Make sure that the option 'Automatically update observations' is enabled
  7. Set the required update rate.


ATT files as tide gauges

  1. Set the Tide method to Tide gauge
  2. Set the number of gauges to use
  3. Select which tide gauges should be used

To set up the Admiralty Tide Tables as online tide gauges see the driver and interfacing manual Admiralty Tide Table (ATT) - 22 for an explanation.

Tide file

  1. Set the Tide method to Tide file
  2. Set the number of gauges to use
  3. Select which Tide gauges should be used and browse for the corresponding Tide files.

Types of tide files

Two types of tide files are supported: tidal data files and regular tide files. (ATT predictions are used as tide gauges, not as tide files.)

The first has extension .qtd and is also used offline. See Processing below.

The second has extension .txt and should have the following format:
24/10/2009 10:10 1.24
24/10/2009 10:20 1.10
24/10/2009 10:30 0.98
(no headers, no extra text to be added)

Note that the online use of the tidal data file is only supported by QINSy versions of 8.10.2012.05.23 and up.

Tide File

Online this option can be used as a 'predicted' tide file.
It is also possible to use this option during Replay with real tidal values.


Processing 

Tidal data is made up of two parts in QINSy software:

  1. The first is the definition file. (See below.)
    This file contains tidal method, station location and identification and the survey lines to be used.
  2. Next is the tidal data. (See below.)
    This is a tidal value with corresponding date and time.

This means that first a tidal definition file needs to be created and at any later stage tidal data can be added to this definition file.

This is all done with the Tide Data Manager, which is part of the Processing Manager.
So eventually the tide will be applied to QPDs.

Location of output file

The output file will be located at <project File>\Tide\TideDefinition folder (or a common files folder as set in Console).

In the Processing Manager, select Tide Data Manager from the Processing Ribbon Tab.
The Tide Data Manager screen appears.


Tide definition file

  1. Click on or select New Tide Definition File from the File menu. The Tide Definition Setup Wizard starts:

  2. First enter a file name in the field “Tide definition file”.
    Use normal keyboard characters and numbers conform to MSWindows file naming conventions.
  3. Under “Tide interpolation method” use the drop down menu to select an interpolation method for the vessel with reference to the tidal station(s).
    Options are:
    Single
    Single tidal method uses one fixed tidal station only. The tidal value is 100% applied to the vessel regardless of position.
    Linear
    Linear tidal method uses multiple stations. The distance from the vessel to each separate station is used when applying tidal values.
    Linear Co Tidal
    Data is shifted based on HW level of two stations
    RWS (RWSLOD)
    Interpolation of four tidal stations. Developed for Dutch Public Works.
    Virtual
    One tidal station. Tidal data is based on vessel position.
    Area
    For different areas a unique tide calculation method can be defined. (See Knowledge Base document How-to Area Method.)
  4. If Linear, Linear Co Tidal or Area is selected, at “Number of tide stations” set the required number of stations to be used.
  5. Under Tide Stations, enter the station name, station ID and Data Type. Select from Manual data, Tide Data file or Simplified ATT.
  6. Repeat this if multiple stations exist.
  7. Click on Next.
  8. On page 2, enter the station coordinates in Easting and Northing. The fields for Latitude and Longitude can be entered, these values are not used for calculations.
  9. Enter the time zone relative to UTC. (east = +, west = -).
  10. Click Next.
  11. Page 3, the survey lines are selected. The line name must correspond to the line name defined in the QPD file!
  12. Add survey lines from a database or manually.
  13. Click “Select”, browse for the line database file. Under linetype, select Single Line or Route. Click the boxes of the intended lines. (use <shift> or <ctrl> to select multiple lines at once). Click OK.
  14. Click Next.
  15. Page 4 gives a summary. Check all entered values and click Finish if ok.

In the tree View of the Tide Data Manager the settings are visible:

Tidal data

Now tidal data can be added to the definition file:

  1. Click on or select New Tide Data file from the File menu. The “Create tide data file” window opens.
  2. Under data type, select Manual Data or Tide Data File. (See below.)


Manual Tidal File

  1. If Manual Data is selected, enter the Time period and Interval.
  2. Click OK. The “New Tide Data File” screen opens:

  3. Under “Tide data file” enter a filename (e.g. location combined with a date).
  4. Enter the Station name or Station ID as defined in the Tide definition file. Easting and Northing will be updated automatically.
  5. The fields “Vertical datum”, “Method” and “Maintenance” are descriptive only. Enter as appropriate.
  6. Under Tide Data enter the values at the correct date and times.
  7. At the bottom, actions can be carried out on the fields:
    Add
    Opens a window to add values at the bottom of the existing list.
    Insert
    Adds a value above the value currently selected at half the interval.
    Delete
    Removes selected values without recalculating the time frame.
    Shift
    Opens a window to shift data in days/hours/minutes (optional backwards in time).
    Enabling: Edit UTC time
    Opens the Time table for editing. Only one field at a time can be changed.
  8. Click OK if all data is correct.

At the bottom part of the Tide Data Manager, a graphical view of the entered tides is seen.


Tide Data File

  1. If Tide Data file is selected, the Import Tide Station Data window appears:

  2. Select the correct Data format:
    YMD HM[S.s] xxx – Any format
    20060207 13:20 1.25
    DMY HM[S.s] xxx – Any format
    07022006 13:20 1.25
    MFPS – Format (MET)
    Format for Dutch Public Works; 3 files needed. (.adm .dat .kwa)
    RIKZ Fixed format
    Format for Dutch Public Works
    PREDUCT – Fixed format
    Specific format for Dutch Navy
    DMYHM xxx MSQ Dialmace format
    070220061320 1.250
    Queensland MSQ HeightData format
    Specific format containing four record types
    ARGOSS – Fixed format
    Date+time xcel format, x.xx m
    FMA – Fixed format
    First is a header and after that columns in the order year month date hour tide (in centimeters)
    2007 9 17 1 43
    HMS - Fixed Format
    HH:MM:SS A.A Bige C.C D.D E
    HH:MM:SS = Time of observation
    A.A = Water level at time of observation
    The other fields are unknown and not used.
    02:03:01 24.47 Bige -0.03 24.5 29
  3. Click on Add, select the file to be imported.
  4. Highlight the filename. Its contents are displayed in the Preview pane.
  5. Under Time offset enter the time difference from UTC to local time.
  6. Under Tide factor enter a scale factor if the height is not in survey units.
  7. Under Tide offset enter a fixed C-O value if applicable.
  8. Click on Import. The data is imported and in the right pane of the Tide Data Manager the file is available.
  9. Highlight the file. In the bottom pane the tidal curve is displayed.
  10. Double click the filename. The “Edit Tide Data” screen opens.
  11. Enter the Station ID. The Station name and coordinates (E/N) are automatically updated.
  12. To import a second tide data file, go to menu File – Import Tide Data.
  13. Repeat steps 1 to 9.

Now one or more tide files are imported.
Before applying the tidal correction, the tidal data itself can be edited:

  1. Move the cursor to the graphical pane.
  2. Use right click to open submenu. Select “Edit Tide data status”.
  3. Use the inside window to de-activate a tidal reading.
  4. Use the outside window to activate a tidal reading.
  5. Alternatively, double click the filename or select Edit Tide Data File from the Edit menu.
  6. In the field status, click right to open submenu. Select OK, Invalid or Predicted from the list.
  7. Click OK once edits are finished. Answer Yes to overwrite. Close the Tide Data Manager.


Tide Processor

Tidal data has been set up. Now it needs to be applied to the QPDs.

  1. In the Processing Manager, select the QPDs to which tide will be applied.
  2. Click on Tide Processor in the Processing Ribbon Tab. The Tide Processor screen is opened.
  3. Click on Start.
  4. The following information should appear: “Initializing”, “Processing QPD file ‘filename’”, list of system names, “Finished processing”, “Successfully applied tide to <number> data file(s).

  5. If this does not appear, something in the definition setup or tidal values, times, dates is incorrect. Repair and try again.
  6. Click on Close.

Return to the Processing Manager.

  1. Load the QPD into the Validator.
  2. In the Profile View, click right and activate “Show raw data”.
    The raw data is displayed. The height difference should be the tidal correction. Move the cursor across the DTM and view the tidal value in the Point Info index.
  3. To compare raw value versus tidal filtered values, right click in Profile View. Select “Apply Tide to Raw data” to overlay the filtered with the raw values.
  4. Tidal correction can be removed. Use Viewed Data=Validated from the Settings menu. And then Reset Tide from the Edit menu. Select All Data.
  5. Close the Validator.

Working on a river

When using the linear method for multiple stations along a river, only use the two nearest stations required.
This method assumes an open water situation with tidal influence from all stations simultaneously.

Linear

The processing works as follows: Per ping (swath) one transducer position, ping time and tide value are stored in the QPD.
The time is used to look up the time interpolated station tide. Next the inverse distance from tide station to ping position is used as a weight to determine a single tide value.
So the closer the position to the tide station the larger the weight and the more influence its tide value has on the calculated tide.
If only one station is used then the weighting process is skipped.

Co Tidal

Per station you can define a time offset, scale factor and offset value. Positive time offset means that the tide lags behind on the station tide, e.g. High tide at station 11:00, in area 11:30, co tidal offset time is +00:30.
The processing works as follows: The ping time with the co-tidal time offset subtracted is used to look up the time interpolated station tide. This value is corrected for scale factor and offset according to the formula Tide = scale factor x ( Station Tide + Offset).
For Co Tidal you can select one or more stations. When multiple stations are used then a distance weighting as explained above is applied to calculate a single value.

Applying tide to an RTK survey

If a survey was done with RTK it's always possible to replay the data and apply the tide afterwards.

When you have tidal data from only one or two stations, the easiest method is to create one or two tidal files and replay your data using these file(s).

First add one or two tide gauges to your recorded database, if they are not available in the database yet. If they are already in the recorded database, check the vertical datum of the fixed node and check the position (position is only necessary when two tide gauges are used).

Add tide gauge(s)

It's not possible to clone new systems to other recorded databases. So if you have multiple databases that need to be replayed with tide, you will have to add a tide gauge individually for each database.
So if you know beforehand that possibly you will want to replay using tide add (a) tide gauge(s) to the template database.

See Database Setup for more information about adding tide gauges to a database.

After that replay your databases using the tidal files. See for more information on how to do that: Tide Data File.

Unreliable Positioning System

Make sure that the position system is set to Unreliable when replaying the database(s).

It is also possible to apply the tide to your QPD files in the Processing Manager.
First you have to replay all your databases with the position system set to Unreliable and create new QPD files.
Then follow the instructions given at Processing. (above)

Info

For offshore operations the heights from a GNSS receiver can be quite accurate, but still have some noise and sometimes even an incorrect height (spike).
The solution is filtering the height and presenting this as a pseudo tide.

To use the RTK Tide for height aiding, please refer to the following document: How-to RTK Height as Tide.