Understanding echograms

The echogram window is split into these areas: the echogram title area, the echogram itself, the integram area, the position status area and the GPS fix area. The integram and position status areas can be hidden.

Echogram window title bar

The title bar is at the top of the echogram window and displays the title of the echogram. The title consists of the echogram's fileset (only for raw variables), the variable name and EV file name.

The transducer frequency will also be displayed in the title, corresponding to the frequency on the Calibration page of the Variable properties dialog box. The transducer frequency will be displayed for virtual variables that satisfy the same criteria.

Echogram area

When first opened, the horizontal axis of the echogram displays one ping per screen pixel, and the vertical axis displays the average of data points, falling within the depth range represented by one screen pixel.

There are many types of echograms, displaying different types of data. What any data point represents depends upon the type of variable being displayed (note, some special data values may be used for the display).

Data values are color coded according to the current Color display minimum and Maximum threshold settings. You can see what colors currently apply by viewing the Color legend dialog box.

The upper and lower display limits of an echogram are determined by the data range of the first ping of the first data file added to the EV file. This can be overridden on an echogram by echogram basis by changing the upper and lower display depth settings on the Echogram Display page of the Variable Properties dialog box.

Lines, regions and a grid, can be superimposed on the echogram, if they have been defined.

Integram area

In the image (above), the green, cyan, and magenta bars are part of the integram area on the echogram. This integram is displaying ping status. The Position status area (indicated by the red box) includes the gray, green and magenta bars for ping position status and colored ticks for GPS fix status.

The integram can display any of:

Ping status
Mean Sv
Maximum Sv
Bottom classification

as selected on the Echogram Display page of the Variable Properties dialog box.

It can also be used to automatically skip to pings that satisfy an Integram Sv threshold condition.

Notes:

The integram area can be used for any classification purpose.
The integram area is only visible if configured on the Echogram Display page of the Variable Properties dialog box.

Position status area

In the above image, the thin strip above the horizontal scroll bar, at the bottom of the Echogram, is the Position status area. The position status area will not be visible if Show position status is not checked in the Echogram page of the EV File Properties dialog box.

This area displays the Position status of each ping according to the following legend:

Ping position status
Green	indicates the position status	'good'
Magenta	indicates the position status	'uncertain'
Gray	indicates the position status	'unknown'

GPS fix status

The upper part of the Position status area shows the GPS fix status for individual pings. Each ping that has an associated GPS fix is indicated by a colored tick showing the status of the fix. The fix associated with a ping is the last fix in time prior to the time of the ping. Only one GPS fix is displayed per ping. The ticks are colored as follows:

GPS fix status
Green	indicates the GPS fix status	'good'
Red	indicates the GPS fix status	'bad'

See Processing GPS data for a detailed information about how GPS fix status and ping position status are defined.