readArgos: Read Argos "DAT" or "DIAG" files

Description

Return a (Spatial) data frame of location records from raw Argos files. Multiple files may be read, and each set of records is appended to the data frame in turn. Basic validation of the data is enforced by default.

Usage

readArgos(x, correct.all = TRUE, dtFormat = "%Y-%m-%d %H:%M:%S",
  tz = "GMT", duplicateTimes.eps = 0.01,
  p4 = "+proj=longlat +ellps=WGS84", verbose = FALSE)
readDiag(x)

Arguments

vector of file names of Argos "DAT" or "DIAG" files.

correct.all

logical - enforce validity of data as much as possible? (see Details)

dtFormat

the DateTime format used by the Argos data "date" and "time" pasted together

timezone - GMT/UTC is assumed

duplicateTimes.eps

what is the tolerance for times being duplicate?

PROJ.4 projection string, "+proj=longlat +ellps=WGS84" is assumed

verbose

if TRUE, details on date-time adjustment is reported

Value

readArgos returns a trip object, if all goes well, or simply a SpatialPointsDataFrame.

readDiag returns a data.frame with 8 columns:

lon1,lat1 first pair of coordinates
lon1,lat1 second pair of coordinates
gmt DateTimes as POSIXct
id Platform Transmitting Terminal (PTT) ID
lq Argos location quality class
iq some other thing

Warning

This works on some Argos files I have seen, it is not a guaranteed method and is in no way linked officially to Argos.

Details

readArgos performs basic validation checks for class trip are made, and enforced based on correct.all:

No duplicate records in the data, these are simply removed. Records are ordered by DateTime ("date", "time", "gmt") within ID ("ptt"). No duplicate DateTime values within ID are allowed: to enforce this the time values are moved forward by one second - this is done recursively and is not robust.

If validation fails the function will return a SpatialPointsDataFrame. Files that are not obviously of the required format are skipped.

Argos location quality data "class" are ordered, assuming that the available levels is levels=c("Z", "B", "A", "0", "1", "2", "3").

A projection string is added to the data, assuming the PROJ.4 longlat - if any longitudes are greater than 360 the PROJ.4 argument "+over" is added.

readDiag simply builds a data.frame.

References

The Argos data documentation was (ca. 2003) at http://www.argos-system.org/manual. Specific details on the PRV ("provide data") format were found in Chapter 4_4_8, originally at 'http://www.cls.fr/manuel/html/chap4/chap4_4_8.htm'.