How-to Use/Setup RTK Tide

If you use RTK-Tide in Qinsy, you are filtering the Height of the waterline, calculated based on:

• GNSS Height;

• Offsets to COG;

• HADR (Height Above Draft Reference) - Height difference between COG and Draft reference;

• Draft;

• Heave;

• Squat (if used).

This calculated Height can then be used as a Tide input.

In case you would like to know more on how this is calculated exactly, please have a look at the following document: How-to Height - Tide and RTK

There are several situations in which you might want to use this:

1. I want to use RTK-Tide since my GNSS is not always accurate enough
   See info box below.

2. I want to use RTK tide and Tide as backup
   See info box below.

3. I want to use Tide (more accurate) and want to use the filtered GNSS height as a backup

For each of the three situations, you will need to setup your Computations slightly different.
More info on this can be found here.

The following situations might be a reason to use RTK-Tide instead of just using the GNSS height directly:

• Your GNSS height is noisy and you would like to average out the noise;

  • This could be due to bad RTK reception;

  • This could also be because the PPP correction is too noisy.

• Your GNSS height is sometimes showing jumps which can be filtered out;

Note that you could also consider:

• Improving the reception of your correction signal;

• Post Processing your Positioning data;

• Using an INS, with possible additional inputs (DVL for example), to improve position results.

Most of the time there is not need to use this.

• Accurate Height input
  If you GNSS/INS is working fine (no jumps) and accurate enough to meet the survey specifications. This can be by using an RTK correction, but for some surveys PPP corrections would already be sufficient.

  • Using RTK-Tide will not give you a higher precision/accuracy.

• Tide input
  In case your GNSS is not accurate enough in Height and your Tide input is accurate enough, you can just use that. The tide values coming from a nearby tide station are then more accurate then filtering a waterlevel based on a GNSS signal that is not receiving corrections (several meters).

• Post Processing
  In case you are post processing your data, RTK Tide will not have an effect on the end result since the newly calculated position track will be more accurate.

• The GNSS of the primary computation is set to Unreliable;

• The GNSS of one of the lower priority computations is set to Accurate;

• RTK Tide is set to the highest priority in the Tide tab:

  

• The GNSS of the primary computation is set to Unreliable;

• The GNSS of one of the lower priority computations is set to Accurate;

• It is important that you set Thresholds on your GNSS system in the Accurate computation.
  This so it fails when RTK corrections for example are no longer received and then Tide can take over.

  

• Setup your Tide strategies in order, below the RTK tide as shown below:

  

• The GNSS of the primary computation is set to Unreliable;

• The GNSS of one of the lower priority computations is set to Accurate;

• Setup your Tide strategies in order, RTK Tide should be below the tide strategies:

  

The RTK Tide will automatically be added as an Observation in the database.
This observation can be used in the same way as any other observation in Qinsy.
It can be found under Computed Height of the Object.

Alert Display

By adding an alert, it is possible to visualize in real time if the available tide strategies are working.

Select the Add alerts Button as shown below:

The Tide Strategies can be found under the Computation results, where you will have to select:

• Computation: Pull down menu with list of available computations for this condition. If the priority computation is selected, the alert display is automatically updated when the steered node changes.

• Vessel: Which Vessel to monitor the tide strategies for.

• Tide Strategies: Choose which of the available tide strategies to select, 

Info

If the selected Tide computation is working it will display an 'OK' otherwise it will display a red 'Alarm'

Observation Physics

Timeplot

It is also possible to select the RTK Tide value using the Generic Layout Editor.
The value can be shown in a Display, in a Logfile or Export file and can be output to another system.

In the Generic Layout Editor select the RTK Tide Value under Observation Systems from Raw Data.

Info

Note that this item is the same as item Tide under Height Aiding, or as the item Tide under Tide Results.

Generic Display

Generic Output

Generic Output 

For more information on setting up a Generic output, please refer to our Drivers Manual:

• Output Systems: Generic Output (User-defined ASCII) - 15

Generic Export

Depending on the information you want to export, you will need related source files like:

• QPD

• DB and Res(ults) 

Any combination is possible when available, but be aware that some RAW data are not available for export.

QPD Export

Help for Generic Display Layout Editor

More information on the use of the Generic Editor can be found in this part of the Knowledge Base: Generic Layout Editor.