position.hac: Read geographic position data from an HAC file

In echogram: Echogram Visualisation and Analysis

Description

This function imports time and geographic positions recorded by a GPS in an HAC file during data acquisition.

Usage

 position.hac(hac)

Arguments

hac	name of an HAC file

Details

The function looks for the Position tuple (20) in the HAC file, and if found, imports the time, latitude and longitude of GPS fixes stored in the digital echogram, as well as the CPU time of the acquisition PC.

Value

A data frame with four variables:

time.gps	date and time from the GPS during data acquisition.
time.cpu	date and time from the computer CPU during data acquisition.
lon	longitudes.
lat	latitudes.

Note

If during acoustic data acqusition the PC clock is set to UTC time, as recomended, time.gps and time.cpu will be approximately equal, because a fraction of a second is added to time.cpu to obtain a precision of 0.0001 s.

Author(s)

Héctor Villalobos

References

ICES, 2005. Description of the ICES HAC Standard Data Exchange Format, Version 1.60. Technical Report 278, ICES Cooperative Research Report.

See Also

navigation.hac

Examples

 hacfile <- system.file("hac", "D20150510-T202221.hac", package="echogram")
 pos <- position.hac( hacfile )
 pos

echogram documentation built on Dec. 16, 2019, 9:30 a.m.