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Height 2D -Tide- Settings

When using an unreliable GNSS system, the following settings should be used in Database Setup and in the Computation Setup of the Controller.

The pictures that are displayed are only examples, settings may vary world wide.

Database Setup settings

Define the Mean Water Level Model in the Geodetic Set-up wizard.
If necessary define a relative correction model, e.g. river lines, or one of the predefined options.
If necessary enter an Height Offset.
The final MWLM is a combination of these three entries.

REMINDER: these settings are used for height aiding in the computation of position. Computed heights may not be referenced to the same reference plane as heights that are published.

Define the Chart/Vertical Datum parameters using the Geodetic Set-up wizard.
If necessary define a relative correction model, e.g. river lines, or one of the predefined options.
If necessary enter an Height Offset.

REMINDER: these settings are used to define the reference plane of the published heights, which may not correspond to the computed heights.

Define the Height above draft reference (HADR) in the Object Definition wizard.

HADR is used in determining the height aiding observation and in computing the actual water level.

Define a Squat Method in Object Definition wizard (optional, not always necessary or available).
Squat is used in determining the height aiding observation and in computing the actual water level.

Qimera does not currently support the following Qinsy Squat methods:

  • Froude
  • Barras
  • Polynomial

A Speed vs Squat table defined in the Qinsy DB setup will transfer over to Qimera successfully.

Define the Positioning system, and the Receiver Positions in the Driver Setup.

Make sure to check what the reference datum is for the receiver data output. It is not always WGS84.

Define the exact locations of all sensors relative to the CoG.

Define a (number of) Tide Gauge(s) in the Database Setup - System.

Ensure the correct vertical datum is selected as the reference for tide observations.
For example, if a tide station outputs water level relative to LAT, then the LAT model should be selected as Vertical Datum for the fixed tide station node connected to the tide observation.
If a tide station outputs the water level relative to a local datum, then this local datum must be selected as Vertical Datum for the tide station node connected to the observation.
In the example EGG2008 (Europe) is selected as the Vertical datum, and the relative height correction model is LAT-NZ (Noordzee). This means tide observation values are referenced to LAT-NZ.

Computation Setup settings

Set the Height status of the positioning system in the Online - Settings - Computation Setup to "Unreliable".

The Height Aiding Observation will be used in the positioning computation in place of the height component of the (GNSS) positioning system.

Set the correct Priority for the heave sensors on the object (only in case of a redundant system).

Enable and set the correct Tide method and Tide gauges.

Enter the Manual draft of the vessel if no draft sensor is available. Otherwise enable the draft sensor.


Change of draft

The draft can change and should be adjusted Online whenever this is the case

Enable and set the Squat method if one was defined in Database Setup.


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Example 2D Positioning - Unreliable Height Status

Vessel Only


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Vessel + Towed Fish


DescriptionComputation
When the height component of position is not used in the computation, the vessel CoG is initially assumed to lie at the water line.Ht. CoG = 0.00
When draft is measured the CoG Height above water line is determined.Ht. CoG = 0.00 - (Draft - HADR)
Ht. CoG = 0.00 - ((+1.70) - (+2.20))
Ht. CoG = +0.50
Squat affects the CoG Ht. value. In this case squat lowers the CoG by 0.15.Ht. CoG = +0.50 - Squat
Ht. CoG = +0.50 - 0.15 = +0.35
Water level includes a Heave component to yield the CoG Ht. above mean water level.Ht. CoG = +0.35 + Heave
Ht. CoG = +0.35 + (+0.70) = +1.05
CoG Ht. must be referenced to a vertical datum, in this case to LAT - NZ (Noordzee), by adding the measured tide value.Ht. CoG = +1.05 + Tide
Ht. CoG = +1.05 + (+4.50) = +5.55
To compute the height of Actual Water Level (AWL) relative to LAT - NZ, subtract the CoG Ht. above water level.Ht. CoG = +5.55 - Ht. CoG wrt Water Level
Ht. CoG = +5.55 - (+0.35) = +5.20
To compute Mean Actual Water Level (MAWL) relative to LAT - NZ subtract Heave from AWL.Ht. CoG = +5.20 - Heave
Ht. CoG = +5.20 - (+0.70) = +4.50
To compute Fish Ht. relative to AWL, subtract the measured fish depth.Ht. CoG = +5.20 - Fish Depth
Ht. CoG = +5.20 - (+6.30) = -1.10
To compute Fish Ht. relative to AWL, subtract the measured fish depth.Ht. CoG = +4.50 - Fish Depth
Ht. CoG = +4.50 - (+6.30) = -1.80



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Generic Display Parameters

ParameterDescription

Comment

User-defined free text


Time

Update time (UTC) of the height aided observation


Vessel Name

Name of the vessel (object), as entered in Db Setup


Height

Value in survey units of the Height Aided Observation, which is calculated by the Height Aiding driver.
Note that the Driver is always present in the windows task bar irrespective of the Height Status (Accurate or Unreliable) selected.

The Height value is by default referenced to the Vertical Datum (also known as Chart Datum), but, alternatively, either Survey Datum or datums like WGS84, ETRS or ITRF (which all use the GRS 1980 ellipsoid) may be selected.

Notice that this value is the same as the height of the reference node for the selected vessel.

Datum:

  • Survey Datum
    Height value is referenced to the selected survey datum ellipsoid, e.g ED50.
    Survey datum is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page.
  • WGS84/ITRF/ETRF
    Height value is referenced to the WGS'84 datum.
    Notice that WGS84 must be one of the two selected datums in the template Database Setup, Geodetic Parameters, 1st Wizard page
  • Vertical Datum (default)
    Height value is referenced to the selected vertical datum e.g NAP, De Min Geoid.
    Vertical datum (or Chart Datum) is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page

Height Status

Two possible values: one or zero.

0:    The height aided observation is not used in any of the computations: The height status of the triggering system (located on the selected vessel) is set to Accurate in all available computations.

1:    The height aided observation is used in at least one of the computations. I.e. that the height status of the triggering system (located on the selected vessel) is set to Unreliable in one of the computations.


Height Sd

1 Sigma (68%) A-Priori Standard deviation of the Height Aiding observation


HeaveHeave component of the Height Aided Observation.
Heave Status

Two possible values:
1: Heave component is part of the height aided observation
0:  No heave component, or no height aided observation at all


Squat

Squat component of the Height Aided Observation.


Squat Status

Two possible values:
1: Squat component is part of the height aided observation
0:  No squat component, or no height aided observation at all


Draft

Draft component of the Height Aided Observation.


Draft Status

Two possible values:
1: Draft component is part of the height aided observation
0:  No draft component, or no height aided observation at all


Tide

Tide component of the Height Aided Observation.

Notice that this item is the same as item Tide under Tide Results


Tide Status

Two possible values:
1: Tide component is part of the height aided observation
0:  No tide component, or no height aided observation at all

Notice that this item is the same as item Tide Status under Tide Results


MWL Model

Mean Water Level Model component (often known as Mean Sea Level) of the Height Aided Observation.


MWL Model Status

Two possible values:
1: MWL (Mean Water Level) Model component is part of the height aided observation
0:  No MWL Model defined (in Db Setup), or no height aided observation at all


Depth

ROV Depth component of the Height Aided Observation.


Depth Status

Two possible values:
1: ROV Depth component is part of the height aided observation
0:  No depth component, or no height aided observation at all


Actual Water Level

The actual water level above Survey Datum

For the object's reference node the "Height above Actual Water level"  value is used minus the "Height above Survey/WGS84/Vertical Datum" value.


Mean Actual Water Level

The Actual Water Level (see above) minus the heave of the object, so i.e. the actual water level without the swell influence.

Datum:

  • Survey Datum
    Height value is referenced to the selected survey datum ellipsoid, e.g ED50.
    Survey datum is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page.
  • WGS84/ITRF/ETRF
    Height value is referenced to the WGS'84 datum.
    Notice that WGS84 must be one of the two selected datums in the template Database Setup, Geodetic Parameters, 1st Wizard page
  • Vertical Datum (default)
    Height value is referenced to the selected vertical datum e.g NAP, De Min Geoid.
    Vertical datum (or Chart Datum) is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page

Mean Water Level

The Actual Water Level (see above) minus the heave of the object (swell) and minus the tide.

Datum:

  • Survey Datum
    Height value is referenced to the selected survey datum ellipsoid, e.g ED50.
    Survey datum is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page.
  • WGS84/ITRF/ETRF
    Height value is referenced to the WGS'84 datum.
    Notice that WGS84 must be one of the two selected datums in the template Database Setup, Geodetic Parameters, 1st Wizard page
  • Vertical Datum (default)
    Height value is referenced to the selected vertical datum e.g NAP, De Min Geoid.
    Vertical datum (or Chart Datum) is set in the template Database Setup, Geodetic Parameters, 'Output Datum Parameters' Wizard page

MWL Geoid Height

The current geoid height above survey datum, i.e. geoidal separation..
This is the calculated height value for the vessel location from the Mean Water Level model. This model is selected in your template setup on the first page of the Geodetic Wizard (Datum Parameters, Mean Water Level Model) using the first combobox. Normally you select your Mean Sea Level model there.


MWL Level Height

The current level height above geoid datum.
This is the calculated height value for the vessel location from the Mean Water Level model. This model is selected in your template setup on the first page of the Geodetic Wizard (Datum Parameters, Mean Water Level Model) using the second combo box. Normally you select your River Lines model there.


MWL Height Offset

The height offset above level datum.
This is a fixed offset value as entered in your template setup on the first page of the Geodetic Wizard (Datum Parameters, Mean Water Level Model).



Notice that this item is actually the same item as "MWL Model Height Offset" in the Geodetics Group under SETUP DATA.


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