GEODAS Documentation Headers provide documentation for data files in the various GEODAS Data Exchange Formats.
The Record type in GEODAS Headers is always set to 4, meaning Header Record.
Identifier supplied by the contributing organization, else given by NGDC in a manner which represents the survey data. It consists of 1 to 8 Uppercase Alphanumeric characters with - or / allowed.
GEODAS covers several geophysical database types. Each database
has a digital exchange format which includes both Survey Documentation
(the Header) and data records. For Hydrograpic Survey data:
HYD93 - Hydrographic Surveys Data Format 1993
A unique 8-character identifier assigned by NGDC to each survey in the
database. The scheme for numbering is as follows:
The first 2 characters identify the source (for MGD77 or HYD93)
The first 4 characters identify the platform or project
The last 4 digits are assigned consecutively
The hydrographic parameters collected during this survey. The 2
codes for HYD93 Headers are as follows (in order in the field):
S - Bathymetric Soundings
F - Hydrographic Features
This is the date (YYYYMMDD) when the digital data records were last altered.
Institution, agency or other group which collected the data, or occasionally the group which contributed the data to NGDC.
Each GEODAS Header is made up of 24 80-character records. The last 2 characters of each record is the sequence number, 01 through 24.
The country which originally collected the survey data.
Name(s) of the ship, aircraft, etc. which collected the survey data.
The Platform Type Code, followed by a plain language description,
details the type of platform which collected the data:
0 - Unspecified
1 - Surface ship
2 - Submersible ship
3 - Aircraft
4 - Buoy
5 - Mobile land
6 - Fixed land
7 - Deep tow
8 - Anchored seafloor instrument
9 - Other, specify in platform type field
The Chief Scientist or Hydrogapher is often the final source for information about the survey.
The descriptive name for a survey or set of surveys, as given by the collecting organization. This may contain abbreviations and/or plain language descriptions.
Type of survey operation. (e.g. Basic Hydrographic Survey or Wire-Drag Field Examination)
Year in which field work was started on this survey.
Year in which field work was completed for this survey.
Scale the survey was done in, usually a ratio. If not a ration, assume 1:number. (i.e. 20,000 means 1:20,000)
General area survey is in. (e.g. Gulf of Mexico)
Specific location of this survey. (e.g. Missippi to Texas, Continental Shelf)
Description of quality of survey work. (e.g. Adequate, complete)
Status of survey work when this data was supplied. (e.g. Evaluated, inspected, approved)
Navigation methods used, as well as navigation instrumentation. (e.g. Satellite, NAVSTAR GPS System)
For the records in this file, the horizontal datum to which the
associated geographic positions are referenced.
NOS01 - Bessel Spheroid 1841-80
NOS02 - Clarke Spheroid of 1866
NOS03 - Astronomic Datum (General)
NOS04 - United States Standard Datum 1901
NOS05 - North American Datum 1913
NOS06 - North American Datum 1927
NOS07 - Old Hawaiian Datum
NOS08 - Kauai Datum
NOS09 - Lisanski 1931 (Field)
NOS10 - Laysan 1930 (Field)
NOS11 - Gardners Pinnacles 1929 (Field)
NOS12 - French Frigate Shoal 1928 (Field)
NOS13 - Necker 1928 Datum
NOS14 - Nihoa 1928 Datum
NOS15 - Vigan Datum
NOS16 - Luzon Datum 1911
NOS17 - San Juan Astro Datum 1901
NOS18 - Puerto Rico Datum
NOS19 - Limon Bay - Colon 1877
NOS20 - Panama Harbor Panama Cathedrl 1877
NOS21 - Panama - Colon Datum 1911
NOS22 - Valdez Datum
NOS23 - Unalaska Datum
NOS24 - Southeast Alaska Datum
NOS25 - Aleutian Islands Datum
NOS26 - Nushagak Bay Datum
NOS27 - Cape Newenham Datum
NOS28 - Norton Sound Datum
NOS29 - Port Clarence and Pribilof Islands
NOS30 - North American Datum of 1902
NOS31 - North American Datum of 1983
NOS32 - Guam 1963 Datum
NOS33 - World Geodetic System (WGS) 1972
NOS34 - World Geodetic System (WGS) 1984
NOS35 - Johnston Island 1961 Astro Datum
NOS36 - Maro Reef Astro Datum 1930 (Field)
NOS37 - Bosun Astronomic Datum 1941 Field
NOS38 - Preliminary North American 1927
NOS39 - Palmyra Atoll - Astro Datum 1944
The horizontal datum to which the geographic positions of the orignal survey data were referenced. (see codes above)
Identifies the vertical datum to which the HYD93 sounding data
is referenced.
00 - Undetermined vertical datum
01 - Mean Sea Level
02 - Mean Low Water
03 - Mean Low Water Springs
04 - Mean Lower Low Water
05 - Mean Lower Water Springs
06 - Lowest Normal Low Water
07 - Lowest Low Water
08 - Indian Spring Low Water
09 - Great Lakes Low Water
10 - Low Lake Level - Lake Champlain
11 - Normal Pool Level - Cayuga & Seneca Lakes
12 - Hudson River Datum
13 - Normal Lake Level - Franklin D. Roosevelt Lake
14 - Sacramento River - Sacramento to Old Ferry
15 - Columbia River Datum
16 - Local Low Water
17 - Gulf Coast Low Water
18 - Low Water Datum 600.0 ft IGLD-1955 Lake Superior
19 - Low Water Datum 576.8 ft IGLD-1955 L Michigan,Huron
20 - Low Water Datum 571.7 ft IGLD-1955 Lake St. Clair
21 - Low Water Datum 568.6 ft IGLD-1955 Lake Erie
22 - Low Water Datum 242.8 ft IGLD-1955 Lake Ontario
23 - Mystic River Datum
24 - Mean High Water
25 - Low Water Datum 601.1 ft IGLD-1985 Lake Superior
26 - Low Water Datum 577.5 ft IGLD-1985 L Michigan,Huron
27 - Low Water Datum 572.3 ft IGLD-1985 Lake St. Clair
28 - Low Water Datum 569.2 ft IGLD-1985 Lake Erie
29 - Low Water Datum 243.3 ft IGLD-1985 Lake Ontario
Tide range over the survey area, in meters (explicit decimal).
Units used for soundings during original field work. (e.g. fathoms and feet)
Methods used to determine soundings. (e.g. Digital Echo Sounder)
Identifies sound correction procedures used. (e.g. 1Corrected,
Carter's Tables)
0 - Undetermined
1 - Corrected, method follows
2 - Uncorrected, 1463 meters/sec
3 - Uncorrected, 1500 meters/sec
4 - Uncorrected, unknown velocity
5 - Non-acoustic depth measurement
Methods used to process this survey. (e.g. Smooth sheets digitized by N.O.S.)
The format of the HYD93 Standard data records, as described using standard Fortran edit descriptors. (Truncated HYD93 records formats use the same descriptors, but contain only those fields chosen by the user.)
The confines of the survey are represented by 4 values: top latitude, bottom latitude, left longitude, and right longitude. In the HYD93 Headers, these boundaries expand to the next hundredth of a degree (explicit decimal).
Information about the survey not found in the Header fields, or where Header fields are inadequate.