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Simrad EM3000D Head II (R-Theta Format-D) - 20

Description

Driver for Kongsberg Simrad  EM3002(D) / EM3000(D) / EM1002 Multibeam Echosounder datagrams broadcasted over a network. Driver to be used to decode either the XYZ position of the footprints (X-Y-Z Format) or the raw range and angle (R-Theta Format) from either D, F or f datagram.

The Kongsberg Simrad EM3000(D) has 127 (2 x 127) beams, but only valid beams will be broadcast. The EM3002(D) (an improved EM3000) will have a maximum of 254 (2 x 254) beams. The Qinsy driver will restore invalid beams, by resetting all values to 0, except for quality factor and intensity, which are set to the invalid values according to the EM300x manual, i.e. FF Hex and 7F Hex, respectively.

Driver only uses the UTC time tags from the EM300x datagrams so make sure that the EM300x System is synchronized by GPS PPS and that clock telegrams are transmitted from the EM300x.

Required datagrams for EM3000

The EM3000 must send the following datagrams for correct decoding:

Rho-Theta mode: Recommended Mode

F datagram for raw ranges and angles
D datagram for sampling frequency (not included in F datagram)
C datagram to determine internal EM3000 clock drift and offset

X-Y-Z mode

D datagram for position of footprints
C datagram to determine internal EM3000 clock drift and offset

Rho-Theta mode / from D datagram

"Raw-Data" D datagram for raw ranges, angles and sampling frequency
C datagram to determine internal EM3000 clock drift and offset

Required datagrams for EM3002

The EM3002 must send the following datagrams for correct decoding:

Rho-Theta mode: Recommended Mode

F datagram for raw ranges and angles
C datagram to identify the serial number from the main head
R datagram for raw bathymetry storage
(as of Qinsy version 8 the offset from the clock telegram is no longer used for the EM3002)

X-Y-Z mode

D datagram for position of footprints
C datagram to determine internal EM3002 clock drift and offset


"Raw-Data" D datagram is identical to ordinary D datagram except that some variables like for example the beam depression angle are now attitude-uncompensated launching angles. The EM3000 must be set up to output this special type of D datagrams if "Rho-Theta from D mode" is used.
Only use this mode if F datagrams are not available in the EM3000 software version (earlier versions).

Backscatter, or raw seabed image intensity values, are stored in the S datagram.

If you want to decode the backscatter, see the Simrad EM300x for more details.

Important

Driver will stop updating if no C (clock) datagrams are received for more than 30 seconds. This is done to prevent latency related errors. This limitation is activated as soon as the first clock datagram arrives. So for test purposes it is possible to use this driver without receiving the clock telegram but never use it like this operationally.

EM3002 Only: The clock datagram is used to identify the main transducer head's serial number and therefore the clock message must always be activated. If no clock messages are sent then the driver will not decode any bathymetric data. The clock message will only be sent when the Kongsberg PU (Processing unit) receives a ZDA string on its serial port. The clock offset derived from the C telegram is no longer applied in Qinsy 8.