West Coast/Alaska Tsunami Warning Center

Operations Manual

NOAA/NWS/WCATWC

910 South Felton Street

Palmer, Alaska 99645

http://wcatwc.arh.noaa.gov

Section 4.1.3.1: WC/ATWC Data Format

Last Updated: 5/2006

Figure 1 illustrates the byte stream of a typical WC/ATWC data file. The WC/ATWC file structure includes a disk header, a channel header block, and a data block. As shown in table 1, the disk header consists of the first 24 bytes of the file. This data is immediately followed by a series of N 200-byte channel headers. The specific information contained in the channel header is listed in table 2. The data block follows the last channel header and the exact number of bytes in each sequential data channel is determined from the information provided in the corresponding channel header.

A quick way to obtain disk and channel header information is to simply perform a hexadecimal data dump of the file. This is illustrated in figure 2. The bytes are in little endian format and should be read from right to left. For example, the hexadecimal value for the year is found in bytes 1-2 of the disk header. When converting the hexadecimal value to a decimal number, the value D5 07 should be read as 07 D5.

Figure 1 - Byte stream structure for a WC/ATWC data file.

Table 1 - The disk header format used at the West Coast and Alaska Tsunami Warning Center.

DISK HEADER
Byte	Data Type	# Bytes	Parameter	C Structure	Example
1-2	2 byte integer	2	wYear	SYSTEMTIME	1980-2099
3-4	2 byte integer	2	wMonth	SYSTEMTIME	1-12
5-6	2 byte integer	2	wDayOfWeek	SYSTEMTIME	0-6
7-8	2 byte integer	2	wDay	SYSTEMTIME	1-31
9-10	2 byte integer	2	wHour	SYSTEMTIME	0-23
11-12	2 byte integer	2	wMinute	SYSTEMTIME	0-59
13-14	2 byte integer	2	wSecond	SYSTEMTIME	0-60
15-16	2 byte integer	2	wMilliseconds	SYSTEMTIME	0-999
17-20	4 byte integer	4	iNumChans	DISKHEADER	currently set at 200
21-24	4 byte integer	4	iChanSize	DISKHEADER	currently set at 200

Table 2 - The channel header format used at the West Coast and Alaska Tsunami Warning Center

CHANNEL HEADER
Byte	Data Type	# Bytes	Parameter	C Structure	Example
1-6	char	6	szStation[6]	CHNLHEADER	BILL
7-12	char	6	szChannel[6]	CHNLHEADER	BHZ
13-16	char	4	szNetID[4]	CHNLHEADER	IU
17-32	SYSTEMTIME	16	stStartTime	CHNLHEADER	As in disk header
33-40	double	8	dSampRate	CHNLHEADER	20
41-44	long	4	INumSamps	CHNLHEADER	2400
45-48	int	4	iBytePerSamp	CHNLHEADER	4
49-52	int	4	iTrigger	CHNLHEADER	0 or 1
53-56	int	4	iSignalToNoise	CHNLHEADER	5
57-60	int	4	iPickStatus	CHNLHEADER	1
61-64	int	4	iStationType	CHNLHEADER	1
65-72	double	8	dLat	CHNLHEADER	68.0651
73-80	double	8	dLong	CHNLHEADER	166.4524
81-88	double	8	dElevation	CHNLHEADER	299.0
89-96	double	8	dGain	CHNLHEADER	1027600000.0
97-104	double	8	dGainCalibration	CHNLHEADER	0
105-112	double	8	dClipLevel	CHNLHEADER	4194304.0
113-120	double	8	dTimeCorrection	CHNLHEADER	0.0
121-128	double	8	dScaleFactor	CHNLHEADER	0.03
129-132	long	4	IUnused1	CHNLHEADER	NA
133-136	int	4	iUnused1	CHNLHEADER	NA
137-140	int	4	iUnused2	CHNLHEADER	NA
141-148	double	8	dUnused1	CHNLHEADER	NA
149-156	double	8	dUnused2	CHNLHEADER	NA
157-164	double	8	dUnused3