DATA PROCESSING MASK FOR SHIPBOARD ADCP
The purpose of the data processing mask is to provide a
quick summary of the state of a data block. This summary is part
of the block header and is therefore propagated up through the
successive levels of the data base and is available for searches.
For example, if a user requested ADCP data from a given area, and
wanted only fully processed data, the search through the directories
could eliminate blocks with certain data processing mask bits set
to zero, indicating missing stages of processing.
The bits are assigned as follows:
data_proc_mask -----> 0000 0000 0000 0000 0000 0000 0000 0000
key -----> vuts rqpo nmlk jihg fedc ba98 7654 3210
Key process byte-count leftward from rightmost
0 TIME_CORRECTED 0
1 TRANSDUCER_ORIENTATION 1
2 COMPASS_ERROR 2
3 TRANSDUCER_BEAM_ANGLES 3
4 SOUND_SPEED_VEL_COR 4
5 SOUND_SPEED_DEPTH_COR 5
6 GLITCHES_REMOVED 6 # set by "badbin"
7 GLITCHES_CORRECTED 7
8 BOTTOM_SOUGHT 8 # set by "set_lgb"
9 BOTTOM_MGB 9 # set by "set_lgb"
a MGB_SET 10
b DEPTH_RANGE_COR 11
g RELATIVE_PROFILES 16
h REFERENCE_VELOCITIES 17
i VEL_TO_ABSOLUTE 18
j VEL_TO_REF_LAYER 19
k POSITIONS_OPTIMIZED 20
l NAV_SOURCE_GPS 21
m NAV_SOURCE_TRANSIT 22
n NAV_SOURCE_LORAN 23
o NAV_SOURCE_OMEGA 24
p NAV_SOURCE_RADAR 25
*bits "c" through "f" and "q" through "v" not used
0 TIME_CORRECTED This bit is on if the times recorded by the
original data acquisition system have been changed in a
non-trivial way to take into account information about errors
in the data acquisition system clock. A trivial change, that
would not have to be indicated here, would be fixing an incorrect
year.
1 TRANSDUCER_ORIENTATION This bit is on if the alignment between
the transducer and the keel was found to be non-zero, and the
raw u and v velocity components have been rotated accordingly.
2 COMPASS_ERROR This bit is on if the compass errors have been
removed. Such errors could come from a variety of sources
including mounting error (constant offset), uncompensated
latitude or speed error, and Schuler oscillation.
3 TRANSDUCER_BEAM_ANGLES This bit indicates that the velocity
components have been corrected for differences between the
nominal and the actual beam angles.
4 SOUND_SPEED_VEL_COR If the velocity components have been
corrected for differences between the true sound speed at
the transducer and the sound speed that was used by the
instrument, then this bit is on.
5 SOUND_SPEED_DEPTH_COR This bit indicates that depths have been
corrected for the sound speed profile. This will generally
result in depths at slightly irregular intervals instead of
the neat 8-m increments we find so convenient, though inaccurate.
6 GLITCHES_REMOVED Some automatic and/or hand editing has detected
anonmalous velocities and replaced them with BAD flags.
7 GLITCHES_CORRECTED Some automatic and/or hand editing has
detected anomalous velocities and replaced them with interpolated
values, or other guesses as to what they should be.
8 BOTTOM_SOUGHT An attempt has been made to detect the presence
of the bottom in a depth range in which it could contaminate the
profile. Means of detection include looking for a local maximum
in amplitude, looking for wild variations in vertical velocity,
percent good, and/or other variables, and using ordinary depth
sounder records. The bottom so detected, and the corresponding
maximum bin that is thought to be free from bottom-bounce
contamination, are recorded.
9 BOTTOM_MGB The data processor has used the estimated bottom
depth to calculate the maximum bin that is unaffected, which
is recorded.
a MGB_SET The data processor has used depth information together
with a criterion based on percent good and/or other variables
and judgements to recommend profile cutoff points. These are
stored as first and last bin numbers. (Ordinarily, the first
bin would be 1. Exceptions would occur for Ametek data when the
ship is underway, for example).
b DEPTH_RANGE_COR The judgement of maximum good bin (and first
good bin) referred to above has been used to set the depth range.
This should be done taking into account any depth compensation, as
indicated by bit 6.
g RELATIVE_PROFILES The profiles were measured relative to a moving
platform.
h REFERENCE_VELOCITIES The absolute velocity of the platform has
been calculated and stored.
i VEL_TO_ABSOLUTE The absolute velocity of the platform has been
added to the profile velocity (relative to the platform) to give
a best estimate of the absolute profiles.
j VEL_TO_REF_LAYER The profiles have been referenced to a level
or layer at which the velocity is assumed to be zero. The
velocity that was subtracted out should be stored, so that a
user can get back to the original profiles relative to the
platform if one so desires.
k POSITIONS_OPTIMIZED The latitude and longitude stored in the
profile directory are based on both the ADCP data and the other
navigation sources. The platform velocity calculated by
differencing these positions therefore agrees with the stored
platform velocity to within the available precision.
l NAV_SOURCE_GPS GPS navigation used to get the platform velocity.
m NAV_SOURCE_TRANSIT Transit was used
n NAV_SOURCE_LORAN Loran was used
o NAV_SOURCE_OMEGA Omega was used
p NAV_SOURCE_RADAR radar ranging from land or buoys was used
