NMEA Outputs from Scala2

Scala2 outputs data in the following formats.

Marport's proprietary sentence

Scala2 uses the following sentence to output sensor data:

$MPMSD, X, YY, ZZZ, TTT, u, VV.VVV*<chk>
  1. $MP: Talker identifier
  2. MSD: Sentence formatter (Marport Sensor Data)
  3. X, YY, ZZZ: location of the emitting sensor on the trawl gear
  4. TTT: type of sensor data
  5. u: acronym of the unit
  6. VV.VVV: decimal value
  7. *<chk>: checksum. The checksum is a security measure to ensure that the sentence is transmitted accurately. The checksum follows the NMEA specifications (IEC 61162-1 Ed.4).

The following sections give more details about the contents of the sentence.

Sensor location

X, YY, ZZZ specifies the location of the emitting sensor on the trawl gear.
  • X: 1 or 2 letters indicating on which gear the sensor is installed. This is useful only for twin, triple, quad and penta trawl gears.
  • YY: 2 letters indicating the part of the gear where the sensor is installed.
  • ZZZ: numerical code that is a Marport sensor node identifier related to the Mx receiver configuration. It is used in Scala2 to position the sensors in the 3D views.
Type of gear Gear position X
Single T
Twin trawl Starboard ST
Twin trawl Port PT
Triple trawl Starboard ST
Triple trawl Middle MT
Triple trawl Port PT
Quad trawl Starboard ST
Quad trawl Inner starboard NT
Quad trawl Inner port MT
Quad trawl Port PT
Penta trawl Starboard ST
Penta trawl Inner starboard LT
Penta trawl Middle NT
Penta trawl Inner port MT
Penta trawl Port PT
Unknown <Empty>
Trawl gear part YY
Port Door PD
Starboard Door SD
Port Wing PW
Starboard Wing SW
Headrope HR
Footrope FR
Body BO
Cod-end CE

Clumps in twin or triple gears are coded as a starboard door of the trawl:

Clump X, YY Description
Twin trawl PT, SD Port trawl, starboard door
Triple trawl, starboard clump MT, SD Middle trawl, starboard door
Triple trawl, port clump PT, SD Port trawl, starboard door
Quad trawl, starboard clump NT, SD Inner starboard trawl, starboard door
Quad trawl, middle clump MT, SD Inner port trawl, starboard door
Quad trawl, port clump PT, SD Port trawl, starboard door
Penta trawl, starboard clump LT, SD Inner starboard trawl, starboard door
Penta trawl, inner starboard clump NT, SD Middle trawl, starboard door
Penta trawl, inner port clump MT, SD Inner port trawl, starboard door
Penta trawl, port clump PT, SD Port trawl, starboard door

Sensor data types and values

TTT, u, VV.VVV contains the type, unit and value of sensor data.
  • TTT: 3 letter code corresponding to the type of data.
  • u: acronym of the unit.
  • VV.VVV: decimal value.
Data type TTT Unit u Description
Depth DPT meters m Depth of sensor (distance from surface)
Catch CAT %

Currently 0 (sensor OFF) or 100 (sensor ON), unit field is empty

Pitch PIT degrees d

From -90 to 90

Roll ROL degrees d

From -180 to 180

Temperature TMP Celsius degrees c
Spread starboard XST meters m

Distance between the master spread sensor and the slave. If the field is empty, it means “slave lost”.

Spread clump XC1
Spread port XPT
Battery BAT %

From 0 to 100. Unit field is empty.

Speed along SPL m/s ms
Speed across SPX m/s ms
Distance to bottom DTB meters m

Distance from the sensor to the sea floor

Opening OPN meters m

Distance from the headrope to the footrope or from the top to the bottom of the trawl body

Clearance CLR meters m

Distance from the footrope or the bottom of the trawl body to the sea floor

Slant Distance SLD meters m

Distance from the sensor to the hydrophone

Relative Bearing RBR degrees d

Angle from the ownship to the sensor relative to ownship heading

True Bearing TBR degrees d

Angle from the ownship to the sensor relative to True North

Type of gear X, YY, ZZZ, TTT

Single

T,PD,23,XST

Distance between doors

Twin trawl

PT,PD,23,XST

Distance between doors

PT,PD,23,XC1

Distance between port door and clump

PT,SD,26,XST Distance between clump and starboard

Triple trawl

PT,PD,23,XST

Distance between port door and starboard door

PT,PD,23,XC1

Distance between port door and port clump

PT,PD,23,XC2

Distance between port door and starboard clump

PT,SD,26,XC2 Distance between port clump and starboard clump
MT,SD,123,XST Distance between starboard clump and starboard door
Quad trawl PT,PD,23,XST Distance between port door and starboard door
PT,PD,23,XC1 Distance between port door and starboard clump
PT,PD,23,XC2 Distance between port door and middle clump
PT,PD,23,XC3 Distance between port door and port clump
PT,SD,26,XC2 Distance between port clump and middle clump
MT,SD,123,XC3 Distance between middle clump and starboard clump
NT,SD,223,XST Distance between starboard clump and starboard door
Penta trawl PT,PD,23,XST Distance between port door and starboard door
PT,PD,23,XC1 Distance between port door and starboard clump
PT,PD,23,XC2 Distance between port door and inner starboard clump
PT,PD,23,XC3 Distance between port door and inner port clump
PT,PD,23,XC4 Distance between port door and port clump
PT,SD,26,XC2 Distance between port clump and inner port clump
MT,SD,123,XC3 Distance between inner port clump and inner starboard clump
NT,SD,223,XC4 Distance between inner starboard and starboard clump
LT,SD,323,XST Distance between starboard clump and starboard door

Positioning sentences

Scala2 can output NMEA data for trawl door positioning with the following sentences:
  • $PSIMS (Olex)
  • $PTSAL (MaxSea version 12 and SeaPix)
  • $PMPT (TimeZero)
  • $IIGLL (MaxSea version 12, single position sentence)
  • $IITPT (Simrad, single position sentence)

These are examples of PSMIS, PTSAL and IITPT sentences:

$PSIMSn,aaa,M,bbb,M,ccc.c,T,ddd.d,M, hhmmss*hh<cr><lf>
  • $PSIMS: talker identifier + sentence formatter
  • n: 1 = Spread1 (port trawl door when Twin Rig) / 2 = Spread2 (starboard trawl door when Twin Rig).
  • aaa,M: slant range to sensor, in meters (filtered values, no decimals).
  • bbb,M: horizontal range to sensor, in meters (unfiltered values, no decimals). Transmits null fields if depth-sensor is not activated (will calculate horizontal range with manual set depth).
  • ccc.c,T: true bearing (deg.rel.north) to sensor. Requires gyro input for reliable data.
  • ddd.d,M: spread measurement in meters (door to door or door to clump). Transmits null fields if invalid values. Filtered values if sensor's filter is on.
  • hhmmss: time of transmission (time of Spread interrogation). Requires ZDA input from GPS for accurate timestamp.
  • *hh: checksum

$PTSAL,aaa.a,bbb.b,ccc.c, ddd.d,eee.e,fff.f*hh <cr><lf>
  • $PTSAL: talker identifier + sentence formatter
  • aaa.a: horizontal range in meters to sensor 1
  • bbb.b: horizontal range in meters to sensor 2
  • ccc.c: bearing to sensor 1 relative to stern line
  • ddd.d: bearing to sensor 2 relative to stern line
  • eee.e: depth in meters of sensor 1
  • fff.f: depth in meters of sensor 2
  • *hh: checksum

$PMPT,POS,AA,bbb.b,M,ccc.c,T, ddd.d,M,eee.e,M,hhmmss*<chk><cr><lf>
  • $PMPT: talker identifier + sentence formatter
  • POS: position
  • AA: 2 letters code that specifies the part of the gear (SD = starboard door / PD = port door / CL = clump on twin trawl / SC = starboard clump on triple trawl / PC = Port Clump on triple trawl).
  • bbb.b,M: horizontal distance in meters
  • ccc.c,T: true bearing (deg.rel.north) to sensor
  • ddd.d,M: depth below surface distance in meters
  • eee.e,M: distance to bottom in meters if available, or empty
  • hhmmss: time of data (hour-minutes-seconds)
  • *hh: checksum

@IITPT,aaa,M,bbb,P,ccc.c,M<cr><lf>
  • @IITPT: talker identifier + sentence formatter. (TPT = Trawl position true vessel)
  • aaa,M: horizontal range in meters to the target (0 - 4000 m). Requires an active depth sensor on the trawl or manual set depth, if not the slant range will be presented.
  • bbb,P: true bearing to the target (i.e. relative to north). Requires gyro input for reliable data.
  • ccc.c,M is the depth in meters of trawl below the surface (0 -2000 m). Requires an active depth sensor on the trawl or manual set depth, if not the depth field will be empty