US NOAA PTWC, UNESCO-IOC/NOAA ITIC
TSUNAMI WARNING OPERATIONS: SEA LEVEL MONITORING
TIDE TOOL: DISPLAY AND DECODE OF SEA LEVEL DATA TRANSMITTED OVER
THE WMO GLOBAL TELECOMMUNICATIONS SYSTEM
(vers 7.0, April 2009)
Pacific Tsunami Warning Center (NOAA)
International Tsunami Information Center (NOAA-UNESCO/IOC)
Tide Tool is a software application that provides end users with the ability to decode, display, and manipulate
sea level data broadcast over the Global Telecommunications System (GTS) of the World Meteorological
Organization (WMO). Data download through the internet is also available, but is not recommended because
timely, complete delivery of all data packets cannot be guaranteed. Tide Tool is enabled by the Tide.tcl
script and region-specific map clients that provide simple-to-use graphical user interfaces to the
continuously-incoming sea level data streams; the tool uses the Tcl/Tk software package and its BLT
extension. Tcl/Tk is an open source, platform-independent software package offering a powerful shell
programming language and graphical toolkit. getTide, also included with Tide Tool, is a BLT script that can
be used to read and analyze archived sea-level data log files.
The software application was developed and is supported by the US NOAA NWS Pacific Tsunami Warning
Center (PTWC) as an operational tool for the real-time continuous tsunami monitoring in the Caribbean,
Indian and Pacific Oceans. Its primary users are National Tsunami Warning Centres, such as the National
Meteorological and Hydrological Service (NMHS), or other agencies acting in this capacity, and with a
downlink from the GTS or to a data file containing those data formatted in a similar manner. It has been
tested under Unix/Linux, Windows 2000/XP environments since 2005 (and Windows Vista in 2009), and
implemented using a non-GTS ‘ftp’ data transmission protocol in Linux and Windows XP/Vista for tsunami
centers without GTS links. The ‘ftp’ method should be considered non-operational if commercial internet
service is utilized since connection reliability and timeliness, especially during tsunami emergencies, cannot
be guaranteed. A Tide Tool Manual is available providing information on its installation and use.
The primary use of this software is as an operational programme run by tsunami warning centres, or other
operational centres, which need to continuously monitor sea levels. Features of the tool include time series
display, wave arrival time, height and amplitude measurement, tide prediction removal, de-spiking, and
station state-of-health and metadata. Users are able to select which stations to receive and display through
edits to input files or by mouse-selection from a station map. Mouse-clickable functions include the
expansion of the time series to enable easy measurement and logging of the arrival time, wave height and
wave period from the incoming signal. Station and data transmission information, raw data packets, and
station health reports can be viewed from within Tide Tool.
Requirements:
In order to decode and display the data, the following are required:
• Computer running Tcl/Tk software with BLT extension
• Sea level data that are continuously archived into a data file
• Tide.tcl and associated map client software.
Computer and Tcl/Tk software with BLT extension
The software requires the installation of the Tcl/Tk software package and the BLT extension, both of which
are freely available for download and easy to install. The software is able to run under Unix/Linux,
Windows 2000/XP/Vista, and Macintosh OSX (under BSD Unix) operating systems; the preferred platform
is Unix or Linux because of its stability. Use on other platforms is possible as it only depends on the Tcl/Tk
and BLT softwares being available. The software does not require substantial computing power, and can
thus run easily on a Pentium III or higher PC system.
US NOAA PTWC, UNESCO-IOC/NOAA ITIC
Sea level data
The input is assumed to be a continuously-appended, ascii text file containing transmissions of data from
different sea level stations. Each station and its data transmission is described by a unique set of parameters,
including a Satellite Product Headers, Station Platform ID, method of transmission and transmission time,
and file formats (Figure 1).
Figure 1. Sample of transmissions from field station Data Collection Platform (DCP) in formats used by the University
of Hawaii Sea Level Center, Australia National Tidal Centre, and US National Ocean Service, respectively.
SWIO40 RJTD 250015
:ENB 1 #1 M 3908 3908 3910 3909 3911 3909 3912 3910 3913 3913 3917 3917
3917 3917 3915 3918 3914 3917 3912 3913 3913 3913 3912 3913 3911 3908 3908
3905 3909 :ENC 1 #2 3409 3410 3411 3411 3413 3419 3419 3420 3419 3415 3414
3418 3411 3408 3410 3409 3409 3408 3409 3409 3414 3413 3409 3414 3414 3410
3412 3409 3410 3413 :BATTLOAD 0 12.83 :NAME=
91642 46/// /1205 10296 40080 22200 00287
555 77744 A0102 516`3 60029 6315B 03024 83030 00A07 02548 02901 29631 6B090
24520 2400A 13025 90036 00297 317B1 50240 60310 0A190 26230 38002 96317
B2102 37103 100A2 50266 50330 02973 18B27 02331 02800 A3102 70103 10029
8318B 33022 92026 00A37 02736 03401 29831 8B390 22570 2801A 43027 66028
00299 319B4 50222 50230 0A490 27960 34002 98319 B5102 19202 901A5 50282
20380 02983 19B57 02163 03200 BV289 134S1 41249 C0501 22080 00070 23677 44777=
^^33487552
206011307M94168411DZpQ^@@rI}0uW@1[Am@~@BsBYB\AG@BrBYBzAM@BqBZCUAB@BoBZCmA@@BmBZDMAI@BlBZDrAG@BlBZD?A
D@BkBZETAL@BjBZEwAGABhBZ"@qv@oL3@[DvAI4B[5Ad6a`=OE0uVW>ZAnA|BYBkCRCqCsDWDnER"@us@so0uVV>YCqC?DBCtDSD
[DnDxEGEa"@wh@wB
_OLAoP 50+1NN 116W
In general, sea level data is digitized and sampled at the field station. Ideally, the data transmitted for
tsunami monitoring will be 1-minute (or better) averaged data values that are transmitted at least every 15
minutes, or more frequently for stations in tsunami source zones; currently, stations transmit every 3-60
minutes and data averages are at 1-15 minute sampling intervals. The data are transmitted over a number of
different satellites to regional telecommunications hubs of the WMO, and onwards to customers such as the
Pacific Tsunami Warning Center, the Japan Meteorological Agency (JMA), and to any requesting National
Meteorological and Hydrological Service (Figure 2).
Figure 2.
Transmission from the
Data Collection Platform
at the field station to
the warning centres.
In the Indian Ocean, the primary satellites used for transmission from the field station are the Japanese
MTSAT for the eastern Indian Ocean and the EUMETSAT operational satellite system for the central and
western Indian Ocean. In the Pacific, the US GOES and Japan MTSAT satellite systems are used. The
PTWC receives its data through the USA GOES satellite system and the US National Weather Service
US NOAA PTWC, UNESCO-IOC/NOAA ITIC
Telecommunications Gateway (NWSTG) and other dedicated communications links. The satellites are part
of the GTS. The GTS is a semi-private, reliable communications system supported by the 187-member
WMO for the transmission of environmental data, and information messages and / warnings. The GTS is the
primary means by the PTWC and JMA receive sea level data and issue tsunami advisories and warnings.
Tide.tcl
The program is started by typing bltwish Tide.tcl The program decodes the received sea level data that are
found in a single data logging file, creates individual station files containing the decoded data, and starts a
graphical user interface display that allows each station to be displayed as a plot (Figures 3-5). Map clients
for the Caribbean, Indian, and Pacific Oceans display a map from which the user may select one or several
stations to show their time series or other information.
Figure 3a. Caribbean, Indian, and Pacific Map clients showing the coastal and DART stations, with color indicating
when data last received (green = data received within last 7 hrs). Sea level records can be plotted by mouse-selecting
the station and choosing the sensor to plot, or by enabling a ‘zoom’ client to choose and automatically plot several
close-by stations.
US NOAA PTWC, UNESCO-IOC/NOAA ITIC
Figure 3b. Tide.tcl GUI showing all stations that were decoded, arranged by region. Station sensor types, station
metadata, and the raw data packet can also be viewed.
Each time series can be displayed with or
without the tidal signal removed, can be
manipulated using a mouse in order to
zoom/enlarge the time series and to pick an
amplitude or wave period (Figure 4a), and
can be ‘despiked’ to remove spurious ‘bad’
points (Figure 4b).
Figure 4a. Sea level time series showing observed and tide-removed time series. A mouse is used to select the part that
should be enlarged to pick the arrival time.
Figure 4b. De-spike feature.
US NOAA PTWC, UNESCO-IOC/NOAA ITIC
Figure 5. Station metadata, as well as recent raw data
transmissions of the sea level messages and a station
transmission report, are available. A location map and
tsunami travel times near the station are also provided
for reference.
Tide.tcl operates continuously once started. It will check every 20 seconds to see if any new data has
arrived, and if so, it will decode and update the station time series that is plotted. When Tide.tcl is started it
will read data from the current day data log. Tide.tcl will keep up to 24 hours of data. As more data arrives
beyond what Tide.tcl is supposed to hold, it will discard the older data to make room for the new. For each
station, multiple sensors are often available and decoded. The sensor code is given by three letters, where
prs stands for pressure sensor, bub indicates bubbler, rad indicates radar.
For viewing older or archived data log files, getTide is provided with the same features of Tide Tool.
Another tool for viewing the current status of the sea level network and station metadata received by the
PTWC is through the download of a .kml file from http://www.sealevelstations.org/ and viewing by the
Google Earth viewer.
To obtain the software, and for further information and questions, please contact Stuart Weinstein, Asst
Director, NOAA Pacific Tsunami Warning Center (stuart.weinstein@noaa.gov), or Laura Kong, Director,
UNESCO/IOC-NOAA International Tsunami Information Center (l.kong@unesco.org).