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Add ARCHIVE2 format definition, difficult to locate online

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Archived from NCAR:
https://github.com/NCAR/lrose-cedric/blob/master/sprint/source/wsr88d.tape-documentation
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[Image] NEXRAD DOCUMENTATION
----------------------------------------------------------------------------
LEVEL II TAPE DOCUMENTATION
WSR-88D BASE DATA
INTRODUCTION:
Weather Surveillance Radar - 1988 Doppler (WSR-88D), or NEXt Generation
RADar (NEXRAD), Level II data are the base digital data produced by the
signal processor (mean radial velocity, reflectivity, and spectrum width) at
the full spatial and temporal resolution of the radar. Level II data also
contain status messages, performance/maintenance data, volume scan strategy,
clutter filter bypass map, and wideband communication console messages.
These are the same data transmitted over high-speed, wideband communications
to the WSR-88D Radar Product Generator (RPG) for processing by the
meteorological analysis algorithms.
Initially it was thought that Level II recorders would be used at selected
sites, and only when significant weather events were taking place. As system
development progressed, it became evident that the Level II data would be of
vital importance to ensure proper calibration of the radars and for use by
researchers to investigate events in more detail than would be possible by
using the Level III products. The Level II data can also be used to test
revised algorithms that may later be applied to operational use.
The NEXRAD agencies (Departments of Commerce, Defense, and Transportation)
recognized the value of Level II data. In June 1994, the agencies agreed to
record Level II data throughout the WSR-88D network. The Level II recording
is not essential to the operational use of the WSR-88D system. The NEXRAD
agencies agreed to certain procedures to minimize the impact of Level II
data collection on the operations of base weather stations, forecast offices
and FAA control locations. The priority of Level II recorder maintenance,
reloading of tapes and continuous recording of data will be assigned by the
local site management.
RECORDING:
The vast amounts of data collected at the Radar Data Acquisition (RDA) site
made it mandatory that the most economical recording devices and media
available at that time be used. It was determined that EXABYTE tape drives
and 8mm tapes provided the most viable system. Depending on operation of the
radar, the recorder model used, and station requirements, one tape may be
filled every 1.8 days for each site. Data grade tapes are used for recording
and archiving. Initially, sites were equipped with EXABYTE 8200 recorders.
These tapes can contain up to 2.3 gigabytes per tape. Later, EXABYTE 8500
recorders were installed which record at higher density with up to 4.7
gigabytes per tape. Also available are 8500c (capable of recording in a
standard compressed mode), and 8505 which is a half height drive fully
downward compatible. The 8505 records up 4.7 gigabytes in an uncompressed
mode.
PROCESSING AND ARCHIVING:
The Level II recorder system consists of an 8mm reorder, 10-tape jukebox
(automated sequential loading of new tapes), an uninterruptable power supply
ans a controller board seated in the RDA computer. Under jukebox operation
the 10-tape supply will last 11 to 27 days depending on the radar scanning
strategies used. Tapes are received at the National Climatic Data Center
(NCDC) from the individual sites in 10-tape cases. Incoming tapes are
processed on a series of 8505 EXABYTE drives, reblocked, cataloged,
inventoried, and archived. The original tapes are sent to an off-site
storage facility for security back-up to the NCDC NEXRAD files.
SPECIAL NOTE:
The WSR-88D is a very complex system. Program modifications and engineering
changes are rather constant features during the phase-in process. Some early
pre-production models experienced considerable difficulties in the recording
of Level II data. Even today, tapes are received that contain spurious,
erroneous, or illegal configurations. We have attempted to recover as much
data as possible from these problem tapes. The user is cautioned that these
anomalies may be encountered while reading the archive tapes. Special care
must be taken to ensure that illegal configurations do not contaminate any
summaries or statistical studies.
NCDC will be glad to assist in solving problems encountered in reading the
tapes, but technical questions about the data themselves must be addressed
to the:
NWS/Operational Support Facility
Operations Branch
1200 Westheimer Dr.
Norman, OK 73069
Telephone: (405) 366-6530
FAX: (405) 366-6550
Definitive information about all aspects of the Doppler radar is contained
in Federal Meteorological Handbook No. 11 (FMH-11), Volumes A through D.
These may be ordered from the National Climatic Data Center.
DATA AVAILABILITY:
As stated previously, all NCDC archives are being generated on EXABYTE 8505
drives. Users must specify whether they require 8200 or 8500 mode tapes. If
copies are requested in the 8200 mode, two or more output tapes may be
required. A header record will appear on each output tape.
Each 8mm tape records approximately 10 hours of Volume Coverage Pattern 11
(VCP 11), 18 hours of VCP 21, or 40 hours of VCP 31 or 32 using the EXABYTE
8200 mode. Using the EXABYTE 8500 mode doubles both the storage capacity and
number of hours of data possible per 8mm tape.
FORMAT:
HEADER FILE: The first file on tape contains only one 31616 byte record.
This record is called the header record.
HEADER RECORD: This 31616 byte "physical record" is divided into 494
"logical records" of 64 bytes each with position 1 as the first byte.
POSITIONS FORMAT DESCRIPTION
1 - 8 C*8 Always ARCHIVE2
9 - 12 C*4 4-letter site ID. e.g. KLMB
13 - 18 C*6 NCDC tape number. e.g. N00001
19 Blank
20 - 28 C*9 Date tape written. dd-MMM-yy e.g. 19-FEB-93
29 Blank
30 - 37 C*8 Time tape written. hh:mm:ss. e.g. 10:22:59
(local time)
38 Blank
39 - 43 C*5 Data Center writing tape: RDASC or NCDC
(Left justified, blank filled)
44 - 48 C*5 WBAN Number of this NEXRAD site. (This is a unique
5-digit number assigned at NCDC. Numbers are
contained in the NCDC NEXRAD Station History file
(WSR-88D RDA LOCATIONS). The file also contains the
four letter site ID, Latitude, Longitude, Elevation,
and Standard location name.)
49 - 53 C*5 Tape output mode. Current values are 8200, 8500,
8500C
54 - 58 C*5 A volume number to be used for copies and extractions
of data from tapes. The form would be VOL01, VOL02,
VOL03 ....VOLnn.
59 - 64 Blank (Available for future use.)
65 - 31616 May be used for internal controls or other
information at each archive center. Information of
value to users will be documented at the time of tape
shipment.
During the process of copying archive tapes, positions 1-18 and 44-48 will
be duplicated. New values will be written in positions 19-43 and 49-58.
DATA FILES:
A new data file is created upon completion of a volume scan. A data file
contains a title, a complete radar volume scan (360 degree revolutions at
each specified elevation cut) of base data, digital radar data message, and
any control/response messages from the RDA to the RPG. The title is the
first record located in each data file and contains a file name, creation
date, and creation time. After the title record through the remainder of the
data file, variable length records containing base data intermixed with
control/response messages are recorded. Messages and base data are
distinguishable by a message header coded for either digital radar base data
or one of the thirteen types of messages. The message header uses a format
common to both data and messages and is included in each 2432 byte packet.
Depending on the predefined volume scan strategy (selected elevations, sweep
rate, pulse rate etc.) used during the collection period, each data file
could contain either five, six, or ten minutes of base data.
Control/response messages are used during actual operations and are of
limited use for post analyses.
DATA TYPES SUPPORTED WITHIN DATA FILES:
A Concurrent minicomputer serves as the host computer for generation of all
Archive Level II data. Depending on the computer used for reading the tapes,
the data types may be different from those used in the Concurrent system.
The Concurrent computer byte (8 bits) structure places bit 0 as the left
most bit and designates bit 0 as the Most Significant Bit (MSB). Bit 7 for a
byte, bit 15 for a halfword (2 bytes), bit 31 for a fullword (4 bytes) and
bit 63 for a double word (8 bytes) are all the Least Significant Bit (LSB)
for their respective data formats.
Level II is recorded using the following data types:
Unsigned byte (byte) - number ranging from 0-255
Character (C) - Standard ASCII characters
Signed Short Integer (I*2) - Most Significant Bit (MSB) is the sign bit
(bit 0). (1-Negative, 0-Positive).
Signed Long Integer (I*4) - MSB (bit 0) is the sign bit.
Single Precision Real (R*4) - MSB (bit 0) is the sign bit (positive),
bit 1-7 is the exponent in excess-64 notation format, and bit 8-31 is
the fraction field. An example may be helpful:
Starting with 4180 69E8 (hex), the sign bit = 0 (positive), the
exponent = +1 [e.g. 41 (hex) converted to 65 (dec) - 64 (excess 64
notation) = +1], and the fraction 8069E8 (hex) shifted by exponent of
+1 gives 8.069E8 (hex). To convert 8.069E8 (hex) to decimal, start with
the whole number 8 (hex) which in this case equals 8 (dec). Next, the
precision of the fraction .069E8 must be noted. This fraction has 5
digits of precision. Next, the fraction portion in hex (069E8) is
converted to decimal (27112) and divided by 16 raised to the power of
the precision of the fraction (5). In other words 27112/(16**5) =
.02585 plus the whole number 8, gives 8.02585 in decimal.
DATA RECORDS:
Within the data file, base data and control/response messages are stored
using a variable record-length structure. The convention here is to begin
with byte 0 as the first byte. Included as the first record of each data
file is a volume scan title containing the following information:
Bytes Format Description
0-8 C*9 Filename (root) - "ARCHIVE2."
9-11 C*3 Filename (extension) - "1", "2", etc.
12-15 I*4 Modified Julian Date referenced from 1/1/70
16-19 I*4 Time - Milliseconds from midnight (UTC) of the day
when the file was created.
20-23 Unused
All remaining records in the data file are composed of data and
command/response messages which are initially stored in separate 2432 byte
packets within an RDA memory buffer. During the archive process the packets
are copied from memory and grouped together to form a record. Record lengths
are variable and are always sized in multiples of the 2432 byte packets.
During the reblocking process, physical records are set to 31616 bytes (2432
x 13).
The following example shows a portion of one packet which includes
Concurrent computer Channel Terminal Manager (CTM) information, a message
header, and a digital radar data message containing reflectivity only.
0000 0000 0980 0000 0002 0000 04B8 0001
0060 1E9E 04B0 1841 0001 0001 0480 14A2
1E9E 1234 6530 0059 0001 0058 0001 0000
FE89 03E8 00FA 01CC 0000 0001 4180 69E8
0064 0000 0000 0000 0015 0000 0000 0000
0000 0064 0000 0000 0000 FFF4 0064 0000
0000 0000 0000 0000 0000 0000 0000 0000
0000 0000 0000 0000 0000 0000 0000 0000
005A 5A00 0070 6D51 6455 6060 4F54 0040
5C3F 4049 4900 4D42 4349 434E 4B3D 4430
4340 3F3D 4644 4443 3A3D 473F 3A3A 3D3D
3C45 3A43 433C 3E43 413C 393F 3F40 4038
(etc.)
Using the above example, each portion of the packet is described in detail.
Remember, this packet may be one of several contained in one record within
the data file.
Bytes 0-11 (halfwords 1-6) Channel Terminal Manager (CTM)
information:
0000 0000 0980 0000 0002 0000 04B8 0001
0060 1E9E 04B0 1841 0001 0001 0480 14A2 Archive II (the data tape) is a
1E9E 1234 6530 0059 0001 0058 0001 0000 copy of messages or data packets
FE89 03E8 00FA 01CC 0000 0001 4180 69E8 prepared for transmission from the
0064 0000 0000 0000 0015 0000 0000 0000 RDA to the RPG. CTM information is
0000 0064 0000 0000 0000 FFF4 0064 0000 attached to a message or data
0000 0000 0000 0000 0000 0000 0000 0000 packet for checking data integrity
0000 0000 0000 0000 0000 0000 0000 0000 during the transmission process
005A 5A00 0070 6D51 6455 6060 4F54 0040 and is of no importance to the base
5C3F 4049 4900 4D42 4349 434E 4B3D 4430 data (omit or read past these
4340 3F3D 4644 4443 3A3D 473F 3A3A 3D3D bytes).
3C45 3A43 433C 3E43 413C 393F 3F40 4038
(etc.)
Bytes 12-27 (halfwords 7-14) Message Header:
0000 0000 0980 0000 0002 0000 04B8 0001 This information is
0060 1E9E 04B0 1841 0001 0001 0480 14A2 used to identify
1E9E 1234 6530 0059 0001 0058 0001 0000 either base data or one of thirteen
FE89 03E8 00FA 01CC 0000 0001 4180 69E8 types of messages that may follow
0064 0000 0000 0000 0015 0000 0000 0000 in bytes 28 - 2431. This header
0000 0064 0000 0000 0000 FFF4 0064 0000 includes the information indicated
0000 0000 0000 0000 0000 0000 0000 0000 below:
0000 0000 0000 0000 0000 0000 0000 0000
005A 5A00 0070 6D51 6455 6060 4F54 0040
5C3F 4049 4900 4D42 4349 434E 4B3D 4430
4340 3F3D 4644 4443 3A3D 473F 3A3A 3D3D
3C45 3A43 433C 3E43 413C 393F 3F40 4038
(etc.)
Halfword Format Description
7 I*2 Message size in halfwords measured from this
halfword to the end of the record.
8 I*1 (Left Byte) Channel ID:
0 = Non-Redundant Site
1 = Redundant Site Channel 1
2 = Redundant Site Channel 2
8 I*1 (Right Byte) Message type, where:
1 = DIGITAL RADAR DATA (This message
may contain a combination of either
reflectivity, aliased velocity, or
spectrum width)
2 = RDA STATUS DATA.
3 = PERFORMANCE/MAINTENANCE DATA.
4 = CONSOLE MESSAGE - RDA TO RPG.
5 = MAINTENANCE LOG DATA.
6 = RDA CONTROL COMMANDS.
7 = VOLUME COVERAGE PATTERN.
8 = CLUTTER CENSOR ZONES.
9 = REQUEST FOR DATA.
10 = CONSOLE MESSAGE - RPG TO RDA.
11 = LOOP BACK TEST - RDA TO RPG.
12 = LOOP BACK TEST - RPG TO RDA.
13 = CLUTTER FILTER BYPASS MAP - RDA to RPG.
14 = EDITED CLUTTER FILTER BYPASS MAP - RPG to RDA.
9 I*2 I.D. Sequence = 0 to 7FFF, then roll over back to 0.
10 I*2 Modified Julian date starting from 1/1/70.
11-12 I*4 Generation time of messages in milliseconds of day past
midnight (UTC). This time may be different than time
listed in halfwords 15-16 defined below.
13 I*2 Number of message segments. Messages larger than message
size (halfword 7 defined above) are segmented and
recorded in separate data packets.
14 I*2 Message segment number.
Bytes 28-127 (halfwords 15-64) Digital Radar Data Header:
0000 0000 0980 0000 0002 0000 04B8 0001 This information describes the
0060 1E9E 04B0 1841 0001 0001 0480 14A2 date, time, azimuth,
1E9E 1234 6530 0059 0001 0058 0001 0000 elevation, and type
FE89 03E8 00FA 01CC 0000 0001 4180 69E8 of base data included
0064 0000 0000 0000 0015 0000 0000 0000 in the radial. This
0000 0064 0000 0000 0000 FFF4 0064 0000 header includes the
0000 0000 0000 0000 0000 0000 0000 0000 following
0000 0000 0000 0000 0000 0000 0000 0000 information:
005A 5A00 0070 6D51 6455 6060 4F54 0040
5C3F 4049 4900 4D42 4349 434E 4B3D 4430
4340 3F3D 4644 4443 3A3D 473F 3A3A 3D3D
3C45 3A43 433C 3E43 413C 393F 3F40 4038
(etc.)
Halfword Format Description
15-16 I*4 Collection time for this radial in
milliseconds of the day from midnight (UTC).
17 I*2 Modified Julian date referenced from 1/1/70.
18 I*2 Unambiguous range (scaled: Value/10. = KM).
19 I*2 Azimuth angle (coded: [Value/8.]*[180./4096.] = DEG).
An azimuth of "0 degrees" points to true north while "90
degrees" points east. Rotation is always clockwise as
viewed from above the radar.
20 I*2 Radial number within the elevation scan.
21 I*2 Radial status where:
0 = START OF NEW ELEVATION.
1 = INTERMEDIATE RADIAL.
2 = END OF ELEVATION.
3 = BEGINNING OF VOLUME SCAN.
4 = END OF VOLUME SCAN.
22 I*2 Elevation angle (coded:[Value/8.]*[180./4096.] = DEG).
An elevation of "0 degree" is parallel to the pedestal
base while "90 degrees" is perpendicular to the pedestal
base.
23 I*2 RDA elevation number within the volume scan.
24 I*2 Range to first gate of reflectivity data (METERS).
Range may be negative to account for system delays
in transmitter and/or receiver components.
25 I*2 Range to first gate of Doppler data.
Doppler data - velocity and spectrum width (METERS).
Range may be negative to account for system delays in
transmitter and/or receiver components.
26 I*2 Reflectivity data gate size (METERS).
27 I*2 Doppler data gate size (METERS).
28 I*2 Number of reflectivity gates.
29 I*2 Number of velocity and/or spectrum width data gates.
30 I*2 Sector number within cut.
31-32 R*4 System gain calibration constant (dB biased).
33 I*2 Reflectivity data pointer (byte # from the start of
digital radar data message header). This pointer
locates the beginning of reflectivity data.
34 I*2 Velocity data pointer (byte # from the start of digital
radar data message header). This pointer locates
beginning of velocity data.
35 I*2 Spectrum-width pointer (byte # from the start of
digital radar data message header). This pointer
locates beginning of spectrum-width data.
36 I*2 Doppler velocity resolution.
Value of: 2 = 0.5 m/s
4 = 1.0
37 I*2 Volume coverage pattern.
Value of: 11 = 16 elev. scans/ 5 mins.
21 = 11 elev. scans/ 6 mins.
31 = 8 elev. scans/ 10 mins.
32 = 7 elev. scans/ 10 mins.
38-41 Unused. Reserved for V&V Simulator.
42 I*2 Reflectivity data pointer for Archive II playback.
Archive II playback pointer used exclusively by RDA.
43 I*2 Velocity data pointer for Archive II playback.
Archive II playback pointer used exclusively by RDA.
44 I*2 Spectrum-width data pointer for Archive II playback.
Archive II playback pointer used exclusively by RDA.
45 I*2 Nyquist velocity (scaled: Value/100. = M/S).
46 I*2 Atmospheric attenuation factor (scaled:
[Value/1000. = dB/KM]).
47 I*2 Threshold parameter for minimum difference in echo
power between two resolution volumes for them not
to be labeled range ambiguous (i.e.,overlaid)
[Value/10. = Watts].
48-64 Unused.
Bytes 128-2431 (halfwords 65-1216) Base Data:
0000 0000 0980 0000 0002 0000 04B8 0001 This information includes the three
0060 1E9E 04B0 1841 0001 0001 0480 14A2 base data moments; reflectivity,
1E9E 1234 6530 0059 0001 0058 0001 0000 velocity and spectrum width.
FE89 03E8 00FA 01CC 0000 0001 4180 69E8 Depending on the collection method,
0064 0000 0000 0000 0015 0000 0000 0000 up to three base data moments may
0000 0064 0000 0000 0000 FFF4 0064 0000 exist in this section of the
0000 0000 0000 0000 0000 0000 0000 0000 packet. (For this example, only
0000 0000 0000 0000 0000 0000 0000 0000 reflectivity is present.) Base data
005A 5A00 0070 6D51 6455 6060 4F54 0040 is coded and placed
5C3F 4049 4900 4D42 4349 434E 4B3D 4430 in a single byte and
4340 3F3D 4644 4443 3A3D 473F 3A3A 3D3D is archived in the
3C45 3A43 433C 3E43 413C 393F 3F40 4038 following format:
(etc.)
Halfword Format Description
65-294 BYTE Reflectivity data (0 - 460 gates) (coded:
[((Value-2)/2.)-32. = dBZ], for Value of 0 or
1 see note below).
65-754 BYTE Doppler velocity data (coded: for doppler velocity
resolution of 0.5 M/S, [((Value-2)/2.)-63.5 = M/S];
for doppler resolution of 1.0 M/S, [(Value-2)-127.]
= M/S], for Value of 0 or 1 see note below), (0 - 92
gates). Starting data location depends on length of
the reflectivity field, stop location depends on length
of the velocity field. Velocity data is range unambiguous
out to 230 KM.
65-1214 BYTE Doppler spectrum width (coded: [((Value - 2)/2.)-63.5
= M/S], for Value of 0 or 1 see note below), (0 - 920
gates). Starting data location depends on length of
the reflectivity and velocity fields, stop location
depends on length of the spectrum width field. Spectrum
width is range unambiguous out to 230 KM.
Four bytes of trailer characters referred to the Frame
Check Sequence (FCS) follow the data. In cases where
the three moments are not all present or the number of
gates for each moment have been reduced, the record is
padded out to a constant size of 1216 halfwords (2432
bytes) following the trailer characters.
Note:
Any base data value of 0 is data below Signal to Noise Ratio(SNR) thresholds
set for that specific base data. Any base data value of 1 is data considered
range ambiguous (i.e., overlaid).
----------------------------------------------------------------------------
[Image] NEXRAD DOCUMENTATION
----------------------------------------------------------------------------
http://www.ncdc.noaa.gov/pub/data/nexrad/tapeii.html
Created by Dick Cram (dcram@ncdc.noaa.gov)
Last updated 18 April 96