Simrad EY500 configuration

Echoview does not use all EY500 telegrams and requires certain restrictions on the use of some telegrams.

Simrad EY500 telegrams currently used by Echoview

• Q1 (echogram telegram)

• V1 (sample SV)

• W1 (sample power)

• B1 (sample angle)

• E1 (echotrace telegram)

• P1 (sample TS)

• GL (geographical location) telegrams. See Interpretation of Simrad GL Telegrams.

• VL (vessel log) telegrams

• LL (list layer) telegrams are used to obtain date information only

• CS (comment string) telegrams are converted to marker regions

Echogram telegram (Q1) : important restrictions

Data must be logged with "20logR" time-varied gain. If data are logged with 40logR time-varied gain a warning will be given.

Echogram (Q1) telegrams can contain a bottom-referenced echogram in addition to the normal surface-referenced echogram. If bottom-referenced echogram data are available and are of higher resolution than the surface-referenced data, then Echoview can build a composite echogram containing all the data at the maximum available resolution, and covering the range of the surface-relative echogram.

Echoview is not limited to a fixed number of data points, so you can vary the number of surface-relative and bottom-relative data points to best fit your application. The EY500 imposes the following limitations:

• The number of surface-relative data points cannot be more than 700.

• The number of bottom-relative data points cannot be more than 500.

Note: only the bottom-relative data within the range of the surface-relative echogram can be used by Echoview.

For a pelagic survey, you would probably set the number of surface-relative data points to 700 and the number of bottom-relative data points to 0.

For a bottom-classification survey, you could set the number of surface-relative data points to 700 and the number of bottom-relative data points to 500, to give you the maximum data resolution near the bottom. For example:

• DISK/Echogram Menu

• Range = 450

• Range Start = 50

• Auto Range = Off

• Bottom Range = 75

• Bot. Range Start = 50

• No. of Main Val. = 700

• No. of Bot. Val. = 500

• TVG = 20 log R

This will log 700 data points over the range 50m to 500m, and 500 data points between 50m above the bottom and 25m below the bottom. Note that bottom-relative data above 50m or below 500m will not be available within Echoview.

Simrad EY500 time and date considerations

The EY500 does not attach date information to all telegrams. Echoview relies on the date information in the VL and/or LL telegrams for date information. Where date is not available from VL or LL telegrams, the date recorded in the logged DGn file name is used - which may be incorrect. Echoview Software recommends that VL telegrams are turned on at all times while logging data from the EY500. The EY500 vessel log should be set to "SPEED" mode. If data is logged without VL or LL telegrams you should rename the DGn file in the following format: "mmddhhnn.yyyy.DG9", where "mm" is the month, "dd" s the day, "hh" is the hour, "nn" is the minute, "yyyy" is the year, and "9" is the last digit of the year. This will allow Echoview to correctly determine logging time and date.

If you do not have a vessel log connected to the EY500 (a typical situation) then Echoview Software recommends that you set up the Vessel Log menu with a simulated speed and turn on vessel log telegrams. Vessel log telegrams are the only telegrams that contain the date as well as the time. If there are no vessel log telegrams in your data files, then Echoview will rely on the dates embedded in the data file names during logging.

The EY500 stores ping time to a resolution of 0.1 seconds. As a consequence, if the ping rate is greater than 10 pings per second, some consecutive pings will bear the same time stamp. Echoview requires a unique time stamp for each ping and stores time internally to a much greater resolution. If it encounters successive pings with duplicate time stamps, Echoview will add 2 milliseconds successively to the time stamp of each such ping. The resulting pings maintain the order with which they were recorded in the data file but are spaced by 2 milliseconds.

Draft considerations

It may be possible to embed a draft into data by setting a value for the transducer depth. Echoview Software STRONGLY recommends logging data with a transducer depth of zero and using Echoview's transducer geometry to model the draft for processing data.

If you do log data with an embedded draft (that is, a non-zero transducer depth) you should read Logged draft warning before processing your data in Echoview.