sealevel.tuk {oce}R Documentation

Sea-level data set, from Tuktoyaktuk (1975)

Description

This sea-level dataset is provided with in Appendix 7.2 of Foreman (1977) and also with the T_TIDE package (Pawlowicz et al., 2002). It results from measurements made in 1975 at Tuktoyaktuk, Northwest Territories, Canada.

The data set is a test contains 1584 points, some of which have NA for sea-level height. The first point in the set is at time 1975-07-06 0800 GMT. However, the first 15 points of the series have NA for the sealevel value, so that the first non-missing point is at 2300 GMT, or 1600 MST as in Foreman's Appendix 7.2.

Usage

data(sealevel.tuk)

Author(s)

Dan Kelley, after data provided in Foreman's (1977) Appendix 7.2.

Source

The data were extracted from the T_TIDE dataset (which Pawlowicz et al. (2002) seems to have based on Appendix 7.2 of Foreman (1977), to build a test case), edited a bit to get the dates in a format that R could scan, and put into a data file. This file was then used to create sealevel object follows.)

# Note: the data file is not supplied with the package,
# and the 7h offset is to convert from Mountain Standard Time.
tuk <- read.table("tuk/tuk_time_elev.dat", header=FALSE, as.is=TRUE)
time <- as.POSIXlt(strptime(tuk$V1, "%d-%b-%Y %H:%M:%S", tz="GMT")+7*3600, tz="GMT")
eta <- tuk$V2
sealevel.tuk <- as.sealevel(eta=eta, time=time,
                            station.name="Tuktoyaktuk", region="NWT", station.number=6485,
                            longitude=133.0292, latitude=69.43889,
                            year=1975, GMT.offset=0)
#save(sealevel.tuk, file="oce/data/sealevel.tuk.rda")

References

Foreman, M. G. G., 1977. Manual for tidal heights analysis and prediction. Pacific Marine Science Report 77-10, Institute of Ocean Sciences, Patricia Bay, Sidney, BC, 58pp.

Pawlowicz, Rich, Bob Beardsley, and Steve Lentz, 2002. Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE. Computers and Geosciences, 28, 929-937.

Examples

data(sealevel.tuk)
plot(sealevel.tuk$data$time, sealevel.tuk$data$elevation, type='l',
     ylab="Height [m]",ylim=c(-2,6))
legend("topright", legend=c("Tuktoyaktuk (1975)","Detided"),
       col=c("black","red"),lwd=1)
tide <- tidem(sealevel.tuk)
detided <- sealevel.tuk$data$elevation - predict(tide)
lines(sealevel.tuk$data$time, detided, col="red")

[Package oce version 0.1-80 Index]