Raw variables derived from Navico Group Lowrance (sonar log) data files
This page describes the variables that Echoview can derive from Navico Lowrance data files.
- *.slg data
- *.sl2 data
- *.sl3 data
- Using raw variables from Navico Group Lowrance (sonar log) data files
- Data processing
- Calibration settings
- Fileset date and time
- Downscan, Sidescan and Sidescan left/right raw variables
- Track course raw variables
- See also
*.slg data
Derived raw variable may include:
- heading data
- position GPS fixes
- line data sounder detected bottom
- unspecified dB single beam pings Primary
- unspecified dB single beam pings Secondary
*.sl2 data
Derived raw variable may include:
- heading data
- track course data (channel n)
- position GPS fixes
- line data sounder detected bottom
- unspecified dB single beam pings Primary
- unspecified dB single beam pings Secondary
- unspecified dB single beam pings Downscan
- unspecified dB single beam pings Sidescan (channel n)
- unspecified dB single beam pings Sidescan left (channel n)
- unspecified dB single beam pings Sidescan right (channel n)
*.sl3 data
Derived raw variable may include:
- heading data
- track course data (channel n)
- position GPS fixes
- line data sounder detected bottom
- unspecified dB single beam pings Primary
- unspecified dB single beam pings Secondary
- unspecified dB single beam pings Downscan
- unspecified dB single beam pings Sidescan (channel n)
- unspecified dB single beam pings Sidescan left (channel n)
- unspecified dB single beam pings Sidescan right (channel n)
n is an integer for the channel ID.
Using raw variables from Navico Group Lowrance (sonar log) data files
Data processing
Raw variable transducer names may include Echosounder, Image Scan or Transducer. When initally created transducer objects fail to suit your processing needs, use the Dataflow window to associate raw variables with a new custom transducer object.
Many operators in Echoview do not process the unspecified dB format raw variables read from Lowrance data files.
Use the Type conversion operator to convert from unspecified dB to another format. For example, to TS before single target detection or target tracking.
Note that Bottom classification and vegetation analysis features are not available for Lowrance data.
Read the Downscan and sidescan raw variables section below before undertaking data processing with these raw variables.
Calibration settings
The sample values for the raw variables read from Lowrance data files may exceed the threshold for Echoview's operators.
Use the CalibrationOffsetUnspecifieddB and PulseDuration (e.g., 0.1 ms) calibration settings to adjust the sample values for use with Echoview's operators.
Fileset date and time
*.slg files record a time offset relative to the start time of data recording. The absolute start time is not recorded in the file and must be specified. Do this by using the Fileset Properties dialog box and the options to specify a Start time and/or an Apply time offset. If the Start time is not set, Echoview uses a default date of 1/01/1970 and the time offset read from the file. This information is displayed in the Filesets window and on the Details dialog box.
*.sl2 and *.sl3 files record accurate time stamp information and do not require the user to specify a Start time. The start time recorded in the Fileset window includes the time offset of the first ping. Navico software creates files and records start times in the file name. Echoview applies the initial ping offset from the file to the file name start time. As such, the Start time displayed in the Filesets window or in the Details dialog box may be slightly later than the time stamp recorded in the file name.
Downscan, Sidescan and Sidescan left/right raw variables
If available, Echoview reads Downscan and Sidescan raw variables from the data file, and dervies Sidescan left/right raw variables from the latter. However, these are mainly for visualization or experimentation only.
In particular, Sidescan raw variables extend from negative to positive ranges, making them incompatible with many of Echoview's operators. In deriving the Sidescan left and Sidescan right variables, Echoview assumes that the two sides are symmetric and centered at 0 m in range. Echoview inverts the sample range and depth for Sidescan left variables so that they are positive.
Track course raw variables
This is heading data.
See also
Navico Group Lowrance data files
Calibration settings for Navico Group Lowrance data