AutoPilot (with turning track) - NMEA XTE - 15

Setup:

Most settings (green rows) are only to be changed once; when going online for the very first time.

Once everything is set up correctly it may be wise to hide them to prevent changing a setting by mistake, so here you can select to show or hide these setup settings.

Note the third option Show+Advanced Settings: this will invoke on the next row an easy short-cut to access additional advanced settings, which normally only can be found using the dialog's upper-left corner icon menu.

Advanced Settings:

Use the [...] button (or double-click on the row) to invoke the Advanced Settings dialog.

Note that these settings are also accessible via the upper-left corner icon menu.

Go to the Advanced Settings paragraph (below) for a full description.

Format:

Main purpose of this driver is to continuously send track offset information to the Auto Pilot so the unit knows what course to steer to stay on the survey line.

Select here the required output format that your auto pilot unit accepts:

• [ None ]

• NMEA APA format - Autopilot Sentence "A"

• NMEA APB format - Autopilot Sentence "B"

• NMEA RMB - Recommended Minimum Nav Info

• NMEA XTE format - Cross track Error, Measured

• Euro500 format

• RobNav-AP9 format

• RobTrack / STS500 format

• Kongsberg TNT ($PRTNT,X)

A change will be effective immediately and can be seen in the lower Results pane.

Please see the Format Specific Settings below for additional settings that come with the selected format.

This option to select the format is only visible when you didn't specify the required output format in your template database setup, so i.e. only when you've selected driver:
"AutoPilot (with turning track)",
"Network - AutoPilot (with turning track) (UDP)", or
"Network - AutoPilot (with turning track) (TCP)".

Additional Output:

This setting is only visible when one of the NMEA output formats is selected.

The selected NMEA output format can be combined with an additional NMEA RMB/RMC output format in order to support autopilot units requiring this additional information.

Use Virtual Node:

For the best result it may be needed to define a steering node some meters ahead of the vessel (e.g. half the vessel length), or close to a location of the vessel's rotation point.

This all depends on your vessel characteristics / behavior.

Here you may use a 'virtual' calculated node position to influence the performance of the autopilot steering unit.

• No
  Select this option to use the exact position of the selected node. The cross-track error (XTE) will be calculated using this exact position.

• Extend Node Baseline
  Use a position which is defined some distance in front of the vessel (e.g. half the vessel length), in order to calculate the XTE.

• Predict Node Position
  Use a predicted node position in order to calculate the XTE. The prediction position is calculated using the vessel's current speed, COG, heading, rate-of-turn and the user-defined prediction time. When using this mode, it is strongly advisable to enable Kalman filtering in the Controller's Computation Setup.

Baseline Direction:

This setting is only available when using a virtual extended node baseline.

The virtual node will be 'moved' forward over a certain distance, and the direction used should come from the vessel's course over ground (COG) or its heading.

Baseline Length:

This setting is only available when using a virtual extended node position.

Enter a positive value, in survey units, to 'move' the selected node forwards, enter negative to 'move' backwards.

Prediction Time:

This setting is only available when using a virtual predicted node position.

The driver can calculate where the selected node will be, after this 'prediction time' value, in seconds. The calculation is very powerful, because next to the vessel's speed, COG and heading, also the rate-of-turn is used. Realistic results can be expected if you use a prediction time of not more than 60 [sec], and when Kalman filtering is enabled in the Controller's Computation Setup. The distance between the actual node and the predicted position can be monitored in the Results part of the dialog (lower pane).

Notice that there is an option in each Navigation Display, to show the predicted vessel shape. Open a Navigation Display, go to View Properties, Objects, select your vessel object, expand the Trail Settings option and enable 'show prediction'. Enter the same prediction time, and now you may graphically monitor how well the calculated prediction behaves.

Node:

The position of the selected node will be used to calculate the line offset with respect to the current survey line.

• [Steered Node]
  Use the current Controller's steered node. The name of the current steered node can be monitored in the Results part of the dialog (lower pane).

• [Computation Setup]
  Use the node currently selected in the Controller's Driver Output Settings. This name can then also be monitored in the Results part of the dialog (lower pane).
  The Drivers Output Settings can be found inside the Controller via pull-down menu Settings (or shortcut Ctrl+H).

• Node name list
  Select your own node name and computation, totally independent from Controller settings.

Note that it depends on the 'Use Virtual Node' setting whether the exact node position is used, or a 'virtual' one.

Computation:

This setting is only available when you have selected your own node name from the Node list.

• From Priority List
  The first valid computation will be used automatically.

• Computation name list
  Select your own computation name.

Minimum Turn Radius:

Enter the minimum turn radius (in survey units) of the vessel.

In order to calculate a smooth turning track, two turns will be used, one when departing the start-point, one when approaching the stop-point.
The minimum turn radius depends of course on the length and characteristics of your vessel.

If you enter a minimum turn radius of zero, the turning track will always be a straight line from start to stop, so no curves.

Run-Out:

Enter a value in survey units if you want to extend the previous line, prior commencing the first turn of the turning track.

This might be useful to allow e.g. a towed fish to end the previous line.

A negative value is allowed, but not recommended. Note that this extra run-out value comes on top of the value you may have entered in the Controller's Session Setup, to extend the survey line.

Run-In:

Enter a value in survey units if you want to approach the SOL of the new line in a straight line, e.g. to settle the ships attitude.

A negative value is allowed, but not recommended. Note that this extra run-in value comes on top of the value you might have entered in the Controller's Session Setup, to start before the actual survey line.

Auto Turning Track:

• Disabled (Manually)
  A turning track will never be calculated automatically, but you may use the [ Calculate... ] button at any time.

• Always at Linechange
  Whenever the mainline is changed (including reversing the line bearing) in the Controller, a turning track will be calculated to start of the new line, using the current settings.

• Only when Auto Start/Stop Recording
  Depends on the Auto Recording Options as defined in the Controller's Session Setup Storage Control.
  It means that a new turning track will be calculated automatically as soon as the Controller stops recording based on these Auto Recording Rules.
  A typical survey scenario for this setting is when you want a combination of Area based recording and the track-to-follow should be based on the swath coverage from your multibeam.

Start

Here you select the start-point of the turning track.

• Line to Line
  This will calculate a turning track from EOL of the previous line to SOL of the new line.

• Vessel to Line
  This will calculate a turning track from the current vessel position to SOL of the new line.

• Vessel to Swath Coverage
  This option is only available when Auto Turning Track is set to 'Only when Auto Start/Stop Recording'.
  See for detailed information the Swath Coverage settings below.

Stop:

Here you select the end-point of the calculated track, which is the beginning of the new line.

Normally you select "Nearest point on Line", in a rare occasion you might go for the other side, e.g. when the vessel is far away from the new SOL.

Scenario:

A maximum of six scenario's are possible to go from the start to the stop-point.

So when commencing the turning track a vessel may turn to port (left turn) or to starboard (right turn) and approaching the stop-point can also be from port or from starboard.

Use a Navigation Display to view the outcome of the selected scenario.

• Best-Fit (Shortest Track)
  From all scenario's the driver determines the best fit curve: meaning the shortest distance.
  However sometimes it is useful to go for another scenario, e.g. when the current one forces the vessel to go over a shallow area (land) or a jetty.

• L S L
  Left turn, Straight line, Left turn

• L S R
  Left turn, Straight line, Right turn

• R S L
  Right turn, Straight line, Left turn

• R S R
  Right turn, Straight line, Right turn

• R L R
  Right turn, Left turn, Right turn

• L R L
  Left turn, Right turn, Left turn

Note that some scenario's are not always possible (mathematically) with current settings and situation.

NMEA Talker:

Two characters should be entered, and will be part of the first field of the outputted datastring.

For example 'GP' will result in an output string that starts with "$GP". The result can be immediately seen in the lower Results pane of the dialog.

When the Kongsberg TNT ($PRTNT,X) format is required it is recommended to enter 'PR' otherwise the Auto Pilot unit may not recognize the datastring

Unit:

Select the unit of the outputted cross-track error value (XTE).

It is by default set to Meters ('M'), but you may also select Nautical Miles ('N') or International Feet ('f').

XTE Resolution:

The number of decimals for the outputted cross-track error (XTE) value, and is default set to 3.

XTE Offset: ^*)

The outputted cross track error value (XTE) will be appended with this offset and is by default set to 0.0.

You may enter a negative offset value in order to decrease the outputted cross track error.

The entered value will be displayed with a red color if it isn't equal to 0, as an extra reminder to the user.

XTE Scalefactor: ^*)

The outputted cross track error value (XTE) will be multiplied with this scale factor, and is by default set to 1.0.

You may increase this value e.g. to 10 or 100 in order to address high-performance autopilot systems.

Note that if the scale factor is set to zero, the outputted XTE will also be zero.

The entered value will be displayed with a red color if it isn't equal to 1, as an extra reminder to the user.

*) The outputted cross track error value = (actual cross track + XTE Offset ) * XTE Scalefactor

When using a non-default XTE Offset and/or Scalefactor you will see both results in the Cross Track Error field of the Results pane: first the actual cross track error (plus unit) and between brackets the outputted cross track error value.

Track Offset:

Enter a value in survey units.

The outputted off track will be the calculated one MINUS this value.

Track Offset:

Enter a value in survey units.

It will be pasted in field number six of the output datastring.

Maximum Turn Rate:

Enter a value in sec/deg.

It will be pasted in field number seven of the output datastring.

NMEA Talker:

Two characters should be entered, and will be part of the first field of the output datastring.

It is recommended to enter 'PR' otherwise the Auto Pilot unit may not recognize the datastring.

Other characters are allowed but will be colored red to remind the user.

The result can be immediately seen in the lower Results pane of the dialog.

Unit:

Select the unit of the outputted cross-track error value (XTE).

It is by default set to Meters ('M'), but you may also select Nautical Miles ('N') or International Feet ('f').

XTE Resolution:

The number of decimals for the output cross-track error (XTE) value, which is by default set to 3.

XTE Offset: ^*)

The outputted cross track error value (XTE) will be appended with this offset and is by default set to 0.0.

You may enter a negative offset value in order to decrease the outputted cross track error.

The entered value will be displayed with a red color if it isn't equal to 0, as an extra reminder to the user.

XTE Scalefactor: ^*)

The output cross track error value (XTE) will be multiplied with this scale factor and is by default set to 1.0.

You may increase this value e.g. to 10 or 100 in order to address high-performance autopilot systems.

Note that if the scale factor is set to zero, the output XTE will also be zero.

The entered value will be displayed with a red color if it isn't equal to 1, as an extra reminder to the user.

Turn Always to:

Turning Line:

Damping Factor:

Turning Line Offtrack:

• None (Same Track back)
  The new turning track will follow the exact same vessel track from the previous recording.
  In a Navigation Display this path is represented with the blue colored 'center_track'.
  -- This setting is useful to survey the same line multiple times (forward and backward) or e.g. in case of multibeam roll/pitch alignment calibration for a patch test.
  -- Another option is to use 'the same track back' in combination with an additional offset so you can automatically survey an entire area with a fixed line spacing.

• From Overlap Percentage
  The new turning track will follow the outer beam track (port or starboard) from the swath coverage of the previous recording with an additional offset of half the swath width.
  In a Navigation Display the two outer beam paths are represented with a red colored 'port_track' and a green colored 'stbd_track'.

Changing this setting when your vessel is 'outside' the selected survey area will automatically re-calculate the (current) turning track .
When the vessel is 'inside' the selected survey area then nothing will happen yet.

Overlap:

Additional Offset:

This extra offset will always be added to the calculated turning track line.

You may enter a negative value in order to allow extra overlap for the next recording.

Changing the offset when your vessel is 'outside' the selected survey area will automatically re-calculate the (current) turning track .
When the vessel is 'inside' the selected survey area then nothing will happen yet.

Swath Coverage:

This row is only visible in Swath Coverage Mode.

It shows the status whether the driver is collecting outer beam information for the swath coverage or not.

• Idle (x.x sec)
  This status means the driver is not collecting outer beam information yet.
  With other words the Controller didn't start auto recording.

• Collecting (x.x sec)
  The Controller is recording because of the auto recording rules and so the driver collects outer beam information for the swath coverage.
  To emphasize this status the row will be colored green.

The incrementing value between brackets indicates the duration (in seconds) for this status

Node Name:

The name of the selected node which current location is used to determine the cross-track error. When using a virtual node it will be mentioned here.

Node Result:

The current position of the selected node, in grid co-ordinates, which is used to determine the cross-track error. When using a virtual node position, it will be the position of the virtual node.

Predicted Distance:

This result is only visible when using a virtual predicted node position. It reflects the distance between the actual node position and the calculated predicted position, using the prediction time setting, the current heading and rate-of-turn of the vessel.

Vessel Heading / COG:

The current heading and course over ground (COG) of the vessel. The displayed rotation convention (true or grid) depends on the global project settings, which you can set in the Console. When using a virtual predicted node position, the heading will be the predicted heading, also, no COG will be displayed, because it is not calculated for the predicted node.

Line name:

The name of the current line, or the label "Turning Track to" the current line, in case the turning track is used.

Line Bearing / Track Bearing:

Line bearing of the current line and the bearing of the closest section of the turning track.

The displayed rotation convention (true or grid) depends on the global project settings as entered in the Console's Settings.

Cross Track Error:

The calculated distance across (XTE), in survey units, of the current node position and the turning track or mainline.
Value will be displayed on a green colored background when the vessel is starboard of the line and dark red when the vessel is on port side.

Note that when using an additional (non-default) XTE Offset and/or Scalefactor you will see both results: first the actual cross track error and between brackets the outputted cross track error value.

Velocity Across / Along:

The across and along speed of the vessel. The across speed will be positive when heading to starboard, negative when heading to port. The unit depends on the current global project speed unit setting, which can be set in the Console.

Format:

The name of the selected output format. The format can be changed in your template setup.

Note that this row won't be visible when you are able to select the Format in the upper Settings pane.

The ASCII data string that will be outputted to the selected serial COM or network TCP port.

If you disable the checkbox it will put the data output on hold. In that case values will be updated in the Results, but are displayed in gray.

Disabling the data output (temporarily) can be useful to experiment with some settings, without disrupting the Auto Pilot unit too much by sending extreme values to it.

Logging:

This row is only visible when Advanced Setting 'NMEA Logging' is enabled.

Remove...

Calculate...

Update Controller Mainline:

This setting has only effect when in Swath Coverage mode.

This will activate immediately the new turning track as current mainline. So this new mainline is an exact copy of the turning track, based on the swath coverage, but without the turn to the start of it.

Line name will always be 'autopilot_swath_track'

Default setting is Yes.

Track can be found in layer 'ACTIVE' and stored in the project's LineData subfolder with filename 'autopilot.qgfline'.

Keep Mainline History:

This setting has only effect when in Swath Coverage mode.

This will keep a history of all previous calculated turning tracks where each track will be suffixed with an incrementing number.

• Online (default)
  All calculated turning tracks will remain during your online session but will be removed when going offline

• Always
  All calculated turning tracks will remain in the qgfline file and will not be removed when going offline

All tracks can be found in layer 'HISTORY' and stored in the project's LineData subfolder with filename 'autopilot.qgfline'.

Smooth Track Iterator:

This is a filter setting and has only effect when in Swath Coverage mode.

The calculated turning track may be affected by erratic outer beam behavior so in that case you should increase the iterator value to make the track smoother.

The default value will be 1, 0 means no filter strength applied at all.

It is safe to change this value when your vessel is still 'inside' the selected survey area: nothing will happen.
When the vessel is 'outside' the survey area then closing this dialog will automatically re-calculate the (current) turning track.

Smooth Heading Iterator:

This is a filter setting and has only effect when in Swath Coverage mode.

The calculated turning track may be affected by unstable heading behavior of the transducer so use this setting to filter the original heading values.

Note that in general such unstable heading behavior is expected on very small boats (unmanned or autonomous vehicles).

0: means no filter (original heading values)

1: is the default filter strength

4: is the strongest filter strength

5: means that a fixed value is used which is derived from the sailed start to end bearing

It is safe to change this value when your vessel is still 'inside' the selected survey area: nothing will happen. When the vessel is 'outside' the survey area then closing this dialog will automatically re-calculate the (current) turning track.

Section Reducer:

Enable NMEA Logging:

All settings and all navigation data (NMEA) will be logged and therefore can be used afterwards for debugging purposes or reproducing the online behavior of your ASV.

Yes will be the default.

Two files are created and appended automatically every time you come online with the following filename convention:

• DrvOutAutoPilotUI (<System Name>) dd-mm-yyyy.NMEA.log
  This file contains the GGA and HDT representation string for the selected node for each update and the exact formatted string that was being output to the autopilot unit in a sequential order.

• DrvOutAutoPilotUI (<System Name>) dd-mm-yyyy.SETTINGS.log.
  This file contains the drivers dialog settings modifications in a sequential order.

Location will be the current project's LogFiles folder.

Beta Tester:

As a beta tester you'll get access to Abort / Resume Mission functionality.

Use [ Your System Name ]:

This setting has only effect when in Swath Coverage mode.

The swath width of this system will be used when enabled and therefore affects the turning track calculation.
So if you enable more than one system then all outer-beams will be used to determine the maximum width.

This row is repeated for every available singlebeam/multibeam/multi-transducer/laser system defined in your template database setup.

Example for a commonly used setup could be:
the multibeam system will be enabled and a possible defined laser and/or singlebeam system needs to be disabled.

Smooth Bearing Output:

Enabling the Smooth Bearing Output is only recommended to use in Swath Coverage mode.

• Enabled
  This will filter the line bearing field in the NMEA APA, NMEA APB or Kongsberg TNT output format.
  (It has no effect when using other output formats)

• Disabled (default)
  Leave disabled in order to use the exact line bearing of the current section

Which NMEA field is affected when this setting is enabled?

• NMEA APA
  Field #9, 'Bearing origin to waypoint'

• NMEA ABP
  Field #9, 'Bearing origin to waypoint'

• Kongsberg TNT
  Field #9, 'Tangent bearing, degrees true'

Same Direction Threshold:

Maximum Turn Angle:

Turning Track Name Specifier:

When a turning track is used for the cross track error calculation instead of the Controller's mainline then this format specifier is used to name it.
This name is visible in the Line Name row of the Results pane (orange background color) and it will be part of the output when an NMEA format is selected.

Here you may overrule the default naming with your own free text, plus the following format specifiers:

• #L: Current line name

• #P: Project name

• #J: Job Number

The default name for the calculated turning track will be "Turning Track to <current line name>".

Note that this track name will be part of most NMEA output formats.

Useful option to overrule the default name in case your autopilot unit does not accept names which are too long.