It’s been a decade since I wrote a script to retrieve observed tide height data from NOAA’s CO-OPS server, which lets you grab up to a month of tide data for a given tide station at a time. In that time, they’ve migrated over to a new server and slightly different API, so it’s probably time to update the script.
The updated version of this script is available in my miscellaneous public R Github as “coops_tide_ht_retrieval_monthly_v3.R”. The current version is copied below. To use it, you’ll need to install the ‘curl’ package in R, and you’ll need to figure out the station number of the tide monitoring station. You can find that at http://opendap.co-ops.nos.noaa.gov/stations/index.jsp . Once you have your station number and the year(s) that you want to retrieve, enter them in the lines below where it says ENTER YOUR STATION ID AND YEARS HERE (around lines 25-28). Then highlight the whole script and run it. The result will be a series of monthly csv files in your current working directory, with 6 minute water level observations (height in meters), with time stamps in UTC (Greenwich Mean Time), and a series of 4 data quality flags for each observation that should hopefully all be ‘0’ if the data quality is sufficient.
# coops_tide_ht_retrieval_monthly_v3.R
# Author: Luke Miller July 2011 - updated 2021
################################################################################
# This script will download a set of verified tide height data from a NOAA
# CO-OPS ERDDAP server and parse it into a data frame to be saved to disk
#
# Station list: http://opendap.co-ops.nos.noaa.gov/stations/index.jsp
# Current server link
# https://opendap.co-ops.nos.noaa.gov/erddap/tabledap/IOOS_SixMin_Verified_Water_Level.html
# Old OPeNDAP server gateway: http://opendap.co-ops.nos.noaa.gov/dods/
# The gateway has links to several other data types available including
# water temperature, air temperature, wind etc.
#
# Six-minute water level data can only be retrieved 1 month at a time. Other
# fields such as water temperature can return up to 1 year at a time.
# The tide height is reported in meters.
###############################################################################
require(curl) # If you don't have this, type install.packages("curl") at the
# R command line before running this script.
require(chron) # for the leap.year function
################################################################################
## ENTER YOUR STATION ID AND YEARS HERE ##
station = 9451600 #Enter your desired station ID here
year = 2018 #Enter the first year of data to get here
year2 = 2018 #Enter the last year of data to get here (can be same as 1st year)
################################################################################
# Example station ID's.
# See http://opendap.co-ops.nos.noaa.gov/stations/index.jsp for a list of all
# stations
#Monterey, CA 9413450
#La Jolla, CA 9410230
#Los Angeles 9410660 (water) 9410647(air/wind)
#San Francisco 9414290
#Point Arena, CA 9416841
#Crescent City, CA 9419750
#Port Orford, OR 9431647
#Charleston, OR 9432780
#Yaquina River, Newport OR 9435380
#Toke Point, WA 9440910
#Neah Bay, WA 9443090
#Sitka, AK 9451600
for (yr in year:year2) {
leap = leap.year(yr) #test if desired year is a leap year
for (mo in 1:12) { #start of mo for-loop
#create text string for month value
if (mo < 10) {month = paste("0",as.character(mo),sep="")} else {
month = as.character(mo)
}
#figure out number of days in month
if ((mo == 4) | (mo == 6) | (mo == 9) | (mo == 11)) {nday = 30} else {
if (mo == 2 & leap == TRUE) {nday = 29} else {
if (mo == 2 & leap == FALSE) {nday = 28} else nday = 31 }
}
startdate = paste(yr,month,"01",sep = "")
enddate = paste(yr,month,nday,sep = "")
#ERDDAP query for 6-minute verified water level looks like this (on 1 line):
#https://opendap.co-ops.nos.noaa.gov/erddap/tabledap/
#IOOS_SixMin_Verified_Water_Level.asc?
#STATION_ID%2C
#DATUM%2C
#time%2C
#WL_VALUE%2C
#I%2CF%2CR%2CT&
#STATION_ID=%229451600%22
#&DATUM%3E=%22MLLW%22
#&BEGIN_DATE%3E=%2220190101%22
#&END_DATE%3E=%2220190131%22
########################################################
###### DON'T CHANGE ANY OF THE CODE BELOW THIS LINE ####
#The parts of the url
url1 = "https://opendap.co-ops.nos.noaa.gov/erddap/tabledap/"
url2 = "IOOS_SixMin_Verified_Water_Level.asc?"
url3 = "STATION_ID%2C" #return stationId
url4 = "DATUM%2C" #return datum
url5 = "time%2C" #return record date-time
url6 = "WL_VALUE" #return water level value
url7 = "%2CI" #return quality flag
url8 = "%2CF" #return quality flag
url9 = "%2CR" #return quality flag
url10 = "%2CT" #return quality flag
#The remaining parts of the url specify how to filter the data on the server
#to only retrieve the desired station and date range. Values must be enclosed
#in ascii double-quotes, which are represented by the code %22
url11 = "&STATION_ID=%22" #station gets added after this
url12 = "%22" # closing quote for station ID
url13 = "&DATUM=%22MLLW%22"#we want MLLW as the datum
url14 = "&BEGIN_DATE%3E=%22" #start date gets added here
url15 = "%22"
url16 = "&END_DATE%3E=%22" #end date gets added here
url17 = "%22"
##### DON'T CHANGE ANY CODE ABOVE THIS LINE ###########
########################################################################
urltotal = paste(url1,url2,url3,url4,url5,url6,url7,url8,url9,url10,url11,
station,url12,url13,url14,startdate,url15,url16,enddate,url17,sep ="")
cat("Contacting server...\n"); flush.console()
con = curl(urltotal) # Open a connection
dat = readLines(con) # Read the returned data
close(con)
cat("Data returned...\n"); flush.console()
Sys.sleep(2) #pause for a few seconds to avoid overloading server
#cleanup
rm(url1,url2,url3,url4,url5,url6,url7,url8,url9,url10,url11,url12,url13,url14)
rm(url15,url16,url17)
con = textConnection(dat) #create text Connection to dat vector
all.lines = readLines(con) #read lines of text into separate slots in a vector
close(con) #close connection to dat vector
if (length(grep('^Error',all.lines))>0) { #check for error in retrieval
cat("There was an error...\n")
cat(dat,"\n") #print contents of dat to show error
flush.console()
} else {
#The column headers are typically preceded by a line of dashes
headerlines = grep("^--------",all.lines) #find index of headers (-1)
#read column header names into a vector
con = textConnection(dat)
headers = scan(con, skip = headerlines, nlines = 1, sep = ",",
what = "character", strip.white = TRUE)
close(con)
#read rest of the data into a data frame 'df'
con = textConnection(dat)
df = read.table(con, skip = headerlines+1, sep = ",", header = FALSE,
quote = "\"", col.names = headers, strip.white = TRUE,
stringsAsFactors = FALSE)
close(con)
###########################################################################
#The following operations will need to be altered if you change the
#fields or data type being returned by the OPeNDAP server
#Convert the time column to POSIX time (seconds since 1970-01-01 00:00:00)
df[,3] = as.POSIXct(df[,3], tz = 'UTC', origin = '1970-1-1')
#Give the columns shorter names
names(df) = c("stationId","datum","TimeUTC","TideHT.m","Flag.Inferred",
"Flag.Flat.Tol","Flag.Rate.Tol","Flag.Temp.Tol")
#Uncomment this if you want to plot the data
#plot(df$TimeUTC, df$TideHT, type = "l",
# xlab = "Date",ylab = "Tide Height, meters")
#Save data automatically to a .csv file.
filename = paste("Station_",station,"_tide_ht_",startdate,"-",enddate,
".csv",sep = "")
write.csv(df,filename,row.names = FALSE, quote = FALSE)
cat("Saved to ",filename,"\n")
flush.console()
#Alternate file save method lets user specify file name at run time
#write.csv(df,file.choose(),row.names = FALSE, quote = FALSE)
#cleanup
rm(dat,con,all.lines,startdate,enddate,filename,headerlines, headers,df,
urltotal)
} #end of if-else statement
} #end of mo for-loop
} #end of yr for-loop
###############################################################################
###############################################################################
cat("Finished\n\a")