Single target pulse properties are output when an export of single targets from a region or a selection is performed from a single target echogram.
The following table details when each pulse property is applicable and available from the different types of single target echograms supported in Echoview.
See: Single target analysis variables for definitions of the variables.
|
Pulse property |
single target detection - single beam |
single target detection - split beam |
single target detection - dual beam |
Simrad single target E telegrams |
HTI .RAW single target echograms |
Precision Acoustic Systems .ts4 single target echograms |
|
Y |
Y |
Y |
Always 6dB |
N |
N |
|
|
Y |
Y |
Y |
N |
N |
N |
|
|
N |
Y |
N |
N |
N |
N |
|
|
Y |
Y |
Y |
N |
Y |
Y |
|
|
Y |
Y |
Y |
N |
Y |
N |
|
|
Y |
Y |
Y |
N |
Y |
N |
|
|
Y |
Y |
Y |
N |
N |
N |
|
|
Y |
Y |
Y |
N |
N |
N |
|
When pulse properties are not applicable or available the "no data" value of -9.90E+37 is output.
The diagrams below describe the pulse properties.
Single target pulse properties in Echoview are normalized to c * t/2.
Where:
t = transmitted pulse length (s)
c = speed of sound (m/s)
The following is the justification for dividing by the factor of 2:
Distance in the water column that the transmitted pulse covers = c * t
Distance in the water column that a received pulse covers if it has a normalized pulse length of 1 = c * t (by definition the same as the transmitted pulse)
The received pulse length however is measured in round-trip terms. That is, the range of any point on a ping graph is determined as follows:
Range = c * t/2
because in the time t, a wave travelling at speed c from the transducer to a scatterer and back again will cover the following distance:
Distance travelled by wave = c * t
and the range of the scatterer is half the distance travelled by the wave front (the wave travelled there and back)
So, when we measure the received pulse length it is on a ping graph, and hence in range space and the following is true:
Echogram range covered by a received pulse if it has a normalized pulse length of 1 = c * t/2
Hence we must normalize to c * t/2 to get a meaningful result.
The reason is, that the distance measured on a ping graph (in echogram range terms) is in fact half of the true physical distance that a pulse occupies in the water column.
In summary, a difference of t (=1 pulse length) in time is a difference of c * t/2 in range.
About Single target detection
Single target detection algorithms