Coerces a dataset (minimally, a sequence of times and heights) into a sealevel dataset. The arguments are based on the standard data format, as were described in a file formerly available at reference 1.
Usage
as.sealevel(
elevation,
time,
header = NULL,
stationNumber = NA,
stationVersion = NA,
stationName = NULL,
region = NULL,
year = NA,
longitude = NA,
latitude = NA,
GMTOffset = NA,
decimationMethod = NA,
referenceOffset = NA,
referenceCode = NA,
deltat
)Arguments
- elevation
a list of sea-level heights in metres, in an hourly sequence.
- time
optional list of times, in POSIXct format. If missing, the list will be constructed assuming hourly samples, starting at 0000-01-01 00:00:00.
- header
a character string as read from first line of a standard data file.
- stationNumber
three-character string giving station number.
- stationVersion
single character for version of station.
- stationName
the name of station (at most 18 characters).
- region
the name of the region or country of station (at most 19 characters).
- year
the year of observation.
- longitude
the longitude in decimal degrees, positive east of Greenwich.
- latitude
the latitude in decimal degrees, positive north of the equator.
- GMTOffset
offset from GMT, in hours.
- decimationMethod
a coded value, with 1 meaning filtered, 2 meaning a simple average of all samples, 3 meaning spot readings, and 4 meaning some other method.
- referenceOffset
?
- referenceCode
?
- deltat
optional interval between samples, in hours (as for the
ts()timeseries function). If this is not provided, andtcan be understood as a time, then the difference between the first two times is used. If this is not provided, andtcannot be understood as a time, then 1 hour is assumed.
Value
A sealevel object (for details, see read.sealevel()).
References
http://ilikai.soest.hawaii.edu/rqds/hourly.fmt (this link
worked for years but failed at least temporarily on December 4, 2016).
See also
The documentation for the sealevel class explains the structure of sealevel objects, and also outlines the other functions dealing with them.
Other things related to sealevel data:
[[,sealevel-method,
[[<-,sealevel-method,
plot,sealevel-method,
read.sealevel(),
sealevel,
sealevel-class,
sealevelTuktoyaktuk,
subset,sealevel-method,
summary,sealevel-method
Examples
library(oce)
# Construct a year of M2 tide, starting at the default time
# 0000-01-01T00:00:00.
h <- seq(0, 24 * 365)
elevation <- 2.0 * sin(2 * pi * h / 12.4172)
sl <- as.sealevel(elevation)
summary(sl)
#> Sealevel Summary
#> ----------------
#>
#> * sampling delta-t: 1 hour
#> * Location: Lat and lon unknown
#> * number of observations: 8761
#> * " non-missing: 8761
#> * Time: 0000-01-01 to 0000-12-31 (8761 samples, mean increment 1 hour)
#> * Data Overview
#>
#> Min. Mean Max. Dim. NAs
#> elevation [m] -2 0.00089588 2 8761 0
#> time -6.2167e+10 -6.2151e+10 -6.2136e+10 8761 0
#>
#> * Processing Log
#>
#> - 2025-04-19 15:29:13 UTC: `create 'sealevel' object`
#> - 2025-04-19 15:29:13 UTC: `as.sealevel(elevation = elevation)`
# As above, but start at the Y2K time.
time <- as.POSIXct("2000-01-01") + h * 3600
sl <- as.sealevel(elevation, time)
summary(sl)
#> Sealevel Summary
#> ----------------
#>
#> * sampling delta-t: 1 hour
#> * Location: Lat and lon unknown
#> * number of observations: 8761
#> * " non-missing: 8761
#> * Time: 2000-01-01 04:00:00 to 2000-12-31 04:00:00 (8761 samples, mean increment 1 hour)
#> * Data Overview
#>
#> Min. Mean Max. Dim. NAs
#> elevation [m] -2 0.00089588 2 8761 0
#> time 946699200 962467200 978235200 8761 0
#>
#> * Processing Log
#>
#> - 2025-04-19 15:29:13 UTC: `create 'sealevel' object`
#> - 2025-04-19 15:29:13 UTC: `as.sealevel(elevation = elevation, time = time)`