Extract environmental data along a trajectory using ERDDAP.

xtracto uses the ERD ERDDAP data web service to extact environmental data along a longitude, latitude and time trajectory

xtracto(dtype, xpos, ypos, tpos = NA, xlen = 0, ylen = 0,
  verbose = FALSE)

Arguments

dtype	- number or string identifying the ERDDAP parameter to extract
xpos	- a real array with the longitudes of the trajectory (in decimal degrees East, either 0-360 or -180 to 180)
ypos	- a real array with the latitudes of the trajectory (in decimal degrees N; -90 to 90)
tpos	- character array with the times of the trajectory in "YYYY-MM-DD". Default is NA for no time.
xlen	- optional real array defining the longitude box around the given point (xlen/2 around the point). Default 0.
ylen	- optional real array defining the latitude box around the given point (tlen/2 around the point). Default 0.
verbose	- optional logical for verbose download out, default FALSE

Value

A dataframe containing:

• column 1 = mean of data within search radius

• column 2 = standard deviation of data within search radius

• column 3 = number of points found within search radius

• column 4 = time of returned value

• column 5 = min longitude of call (decimal degrees)

• column 6 = max longitude of call (decimal degrees)

• column 7 = min latitude of call (decimal degrees)

• column 8 = max latitude of call (decimal degrees)

• column 9 = requested time in tag

• column 10 = median of data within search radius

• column 11 = median absolute deviation of data within search radius

Examples

xpos <- c(230, 235)
ypos <- c(40, 45)
tpos <- c('2006-01-15', '2006-01-20')
xlen <- 0.025
ylen <- 0.025
extract <- xtracto('erdMBsstd8day', xpos, ypos, tpos = tpos, xlen = xlen, ylen = ylen)