The following is a listing of the first file provided on the
magnetic tape distributed by CDIAC. This file provides variable
descriptions, formats, units, and other pertinent information about
each file associated with this coastal hazards data base.

Title of the Data Base

A Coastal Hazards Data Base for the U.S. Gulf Coast
Contributors

Vivien M. Gornitz
National Aeronautics and Space Administration
Goddard Institute for Space Studies
2880 Broadway
New York, NY 10025

Tammy W. White
Oak Ridge National Laboratory
Carbon Dioxide Information Analysis Center
Oak Ridge, TN 37831-6335


Scope of the Data

The 29 data variables within A Coastal Hazards Data Base for the
U.S. Gulf Coast, and the corresponding coastal vulnerability
indices that may be derived, may be used by coastal planning,
research, and management agencies to identify shorelines at risk
from coastal erosion and inundation. This data base should be used
to identify areas where further study is necessary. In addition,
these data may be used in combination with appropriate
climatological data (e.g., Birdwell and Daniels, 1991) to identify
coastal areas that are vulnerable to coastal erosion and inundation
from sea level rise or storm surge.

This data base is comprised of the following data sets: elevation,
bedrock geology, geomorphology, sea level trends, horizontal
shoreline movements (erosion/accretion), tidal ranges, and wave
heights. For several of these data sets minimum, mean, and maximum
data values are available. These data variables may be divided into
two basic classes, one that measures erosion potential and one that
is related to inundation risk. The erosion risk of each coastal
grid cell or line segment may be determined based on geology,
geomorphology, shoreline displacement, tidal ranges and wave
heights, while the inundation risk may be estimated based on sea
level trends and elevations.

Seven of the 29 data variables in this data base are classified
versions of other variables within this data base. The seven
classified risk variables contain "risk values" of one to five for
each coastal grid cell in the data base. These risk variables may
be used to calculate a Coastal Vulnerability Index (CVI) that may
be used to identify areas on the U.S. Gulf Coast that are
vulnerable to sea level rise or coastal erosion.

Data Formats

For ease of use, this data base has been divided into five data
groups or coverages. Each of these five data groups are provided in
two different data formats. The first format is designed for use by
the ARC/INFOTM Geographic Information System (GIS). This format
stores the data as polygons (e.g., GCGRID and GCRISK), as arcs
(e.g., GCLINE and GCOAST), or as points (e.g., GCPOINT). The second
format contains comparable data that has been converted into flat
ASCII data files for use by raster GISs or non-GIS data base
systems.

The first two data groups are registered to a 0.25 degree latitude by
0.25 degree longitude grid. The first, GCGRID (Files 4 and 5) provides
the 22 original data variables, while the second data group, GCRISK
(Files 8 and 9) provides the seven relative risk variables.

The third data group is registered to a 1:2,000,000 digitized U.S.
Gulf coastline, GCLINE (Files 12 and 13), and provides 29 data
variables (i.e., the 22 original and the seven relative risk data
variables).

The fourth data group, GCPOINT (Files 16 and 17), was originally
obtained as point data. This data group provides the source
information used in the development of the tidal range and sea-
level-trends data sets. Data variables included in this data group
are station names/numbers, record lengths, and longitude/latitude
locations of the actual data point. These data represent the
physical location of the occurring data point, and will allow the
precise location of each station used in calculating the gridded
tidal range and sea-level-rise data variables within the 0.25 degree grid
cells of data groups GCGRID and GCRISK.

Finally, the last group contains an auxiliary file, a 1:2,000,000
digitized coastline of the U.S. Gulf Coast, GCOAST (files 20 and 21). 
These line segments are identical to those found in data group GCLINE, 
however no data values are provided.

A description of the contents of each of the data groups and files
included with this data base follows:
 
(1) GCGRID: Gridded polygon data for the 22 original data
variables. Data sets contained in this group include
elevation, geology, geomorphology, sea level trend, shoreline 
displacement (erosion/accretion), tide range, and wave
heights.

(2) GCRISK: Gridded polygon data for the seven classified risk
variables. The risk variables are classified versions of the
following original variables: mean coastal elevation, geology,
geomorphology, local subsidence trend, mean shoreline
displacement, mean tidal range, and maximum significant wave
height.

(3) GCLINE: 1:2,000,000 digitized line segment data for the U.S.
Gulf Coast containing the 29 data variables (i.e., the 22
original data variables and the seven classified risk
variables). Data contained within this group include
elevation, geology, geomorphology, sea level trend, horizontal
shoreline displacement, tide range and wave heights. The seven
risk variables are classified versions of the following
original data variables: mean coastal elevation, geology,
geomorphology, local subsidence trend, mean shoreline
displacement, mean tidal range, and the maximum significant
wave height.

(4) GCPOINT: Point data for the stations used in calculating the
sea-level-trend and tide-range data sets. Data include station
names/numbers, record length, latitude/longitude location, and
mean and maximum data values (when available).

(5) GCOAST: 1:2,000,000 digitized coastline of the U.S. Gulf
Coast. The coastline was extracted from a digitized map of the
United States compiled by the U.S. Geological Survey.

To improve the portability of the information in the data files,
FORTRAN 77 and SASTM input/output routines have been included with
this data base for each of the flat ASCII data files.

These input/output routines are intended to be used to read/write
the data values contained in the flat ASCII data files [containing
the gridded data base, the original point data (for the sea level
trend and tide range variables), and the digitized U.S. Gulf
coastline].

The data groups in this data base are available as compressed and 
uncompressed exported ARC/INFO coverages (Version 6.0.1).  Both
sets of export files contain identical data and must be read into 
ARC/INFO or ARCVIEW using the COVER OPTION of the IMPORT
command.  The compressed export coverages are located in the 
pub/ndp043b subdirectory and were generated using the FULL option
of the ARC/INFO EXPORT command.  These coverages contain ASCII 
compression characters that do not have equivalent EBCDIC  
characters on an IBM computer.  The uncompressed ARC/INFO 
export coverages are IBM compatible and are located in the
pub/ndp043b/asciiexp subdirectory.  These files were generated 
using the NONE option of the ARC/INFO EXPORT command.  Both 
the compressed and uncompressed sets of export files contain
identical data and differ only in file format.  These files
are in a GEOGRAPHIC projection, which means that the coverages
are projected in a spherical reference grid using latitude and
longitude coordinates that are stored in decimal degrees (DD).

The flat ASCII files contain an identical version of this data base.
The gridding method used in this data base consists of  0.25 degree
latitude by 0.25 degree longitude grid cells.  These cells cover the
area defined by the following coordinates: 100 degrees W, 24 degrees N;
100 degrees W, 32 degrees N; 80 degrees W, 32 degrees N; and 80 degrees W,
24 degrees N. The origin of the grid is at 100 degrees W, 24 degrees N, 
and grid identifiers increase from left to right, bottom to top. The data 
contained within each grid cell are an average for the entire grid cell.
The grid cell identification number is located in the center of each
cell and although it is not the physical location of each data
value, it represents averages for all data points located within
the cell.

The flat ASCII versions of the files have been provided to allow
use of these data by users who do not have access to ARC/INFOTM. The
format and contents of each of the flat ASCII files are described in
the following section (the ARC/INFOTM coverages have the same
variables and general format as described herein for the ASCII files).


Data Group GCGRID:

This data group contains gridded data for the 22 original data
variables. These data variables are from the seven data sets and
are as follows: mean, maximum, and minimum elevation, and the
number of 5' grid cells used in deriving the data values; geology;
geomorphology; relative sea level trend, global-trend, corrected
sea level trend, local subsidence trend, and the years of record of
the gauge stations used in calculating these values; mean, maximum,
and minimum shoreline displacement, and the number of 3', 7.5', or
15' grid cells used in deriving the data values; mean and maximum
tidal range, mean tide level, and the number of tidal stations used
in calculating these values; 20 year mean wave height, maximum
significant wave height, and the 20 year mean wave height standard
deviation.

The names of the ARC/INFOTM coverage and flat ASCII files providing
these data are GCGRID.E00 (File 4) and GCGRID.ASC (File 5),
respectively. File 5 is formatted as follows:

  10 READ(5,100,END=999) ID,ELAVG,ELMAX,ELMIN,
     1  ELNUM,GL,GM,SLR,SLG,SLC,SLYR
      READ(5,110) ERAVG,ERMAX,ERMIN,ERNUM,TRAVG,
     1  TRMAX,TRLVL,TRNUM,WHAVG,WHMAX,WHSD
 100 FORMAT(I5,4F8.2,2I4,3F8.2,I4)
 110 FORMAT(3F8.2,I4,3F8.2,I4,3F8.2)

The variables in data group GCGRID (File 5) are shown in Table 8
and are listed as they appear in the file.

Table 8. Variable formats for GCGRID.ASC (File 5).

                 Column
Variable name Start   End  Variable type  Variable description

ID               1      5     Integer     System variable -
                                          grid cell identifier.

ELAVG            6     13     Real        Data variable - mean
                                          elevation of all
                                          positive 5' by 5'
                                          grid cells within a
                                          given 0.25 degree grid
                                          cell; values in
                                          meters.

ELMAX           14     21     Real        Data variable -
                                          maximum elevation of
                                          all positive 5' by
                                          5' grid cells within
                                          a given 0.25 degree grid
                                          cell; values in
                                          meters.

ELMIN          22      29     Real        Data variable -
                                          minimum elevation of
                                          all positive 5' by
                                          5' grid cells within
                                          a given 0.25 degree grid
                                          cell; values in
                                          meters.

ELNUM          30      33     Integer     Data variable -
                                          number of 5' by 5'
                                          grid cells used in
                                          calculating ELAVG,
                                          ELMIN, and ELMAX for
                                          a given 0.25 degree grid
                                          cell.

GL             34      37     Integer     Data variable -
                                          ordinal value
                                          indicative of the
                                          type and resistance
                                          of the rocks within
                                          a given 0.25 degree grid
                                          cell to erosion.

GM             38      41     Integer     Data variable -
                                          ordinal value
                                          indicative of the
                                          type and
                                          susceptibility of
                                          the landforms within
                                          a given 0.25 degree grid
                                          cell to inundation
                                          and erosion.

SLR            42      49     Real        Data variable -
                                          relative sea-level
                                          trend within a given
                                          0.25 degree grid cell;
                                          values in mm/year.

SLG            50      57     Real        Data variable - 
                                          long-term geologic
                                          trend derived from
                                          14C data for each
                                          0.25 degree grid cell;
                                          values in mm/year.
 
SLC            58      65     Real        Data variable -
                                          corrected sea-level
                                          trend. Tide-gauge
                                          data (i.e., SLR)
                                          corrected for
                                          geologic trends
                                          (i.e., SLG) for each
                                          0.25 degree grid cell.

SLS            66      73     Real        Data variable - the
                                          local subsidence
                                          trend. Tide-gauge
                                          data (i.e., SLR)
                                          corrected for the
                                          regional eustatic
                                          rate of sea level
                                          rise (i.e., 1.25
                                          mm/year).

SLYR           74      77     Integer     Data variable -
                                          years of record used
                                          in estimating the
                                          sea level trend for
                                          each 0.25 degree grid cell.


--------------- SECOND LINE READS AS FOLLOWS -----------------


ERAVG           1       8     Real        Data variable - mean
                                          long-term erosion
                                          trend for a given
                                          0.25 degree grid cell;
                                          values in meters.

ERMAX           9      16     Real        Data variable -
                                          maximum long-term
                                          erosion trend for a
                                          given 0.25 degree grid
                                          cell; values in
                                          meters.

ERMIN          17      24     Real        Data variable -
                                          minimum long-term
                                          erosion trend for a
                                          given 0.25 degree grid
                                          cell; values in
                                          meters.

ERNUM          25      28     Integer     Data variable -
                                          number of 3', 7.5',
                                          or 15' grid cells
                                          used in calculating
                                          ERAVG, ERMIN, and
                                          ERMAX for a given
                                          0.25 degree grid cell.

TRAVG          29      36     Real        Data variable -
                                          average of the mean
                                          tide range for all
                                          the gauge stations
                                          that occur within a
                                          given 0.25 degree grid cell
                                          (mean tide range is
                                          the difference in
                                          height between mean
                                          high water and mean
                                          low water in 1988);
                                          values in meters.

TRMAX          37      44     Real        Data variable -
                                          maximum tide range
                                          measured for all
                                          gauge stations that
                                          occurred within a
                                          given 0.25 degree grid cell
                                          in 1988 (this value
                                          may be the "spring"
                                          or "diurnal" tide
                                          range, depending on
                                          geographic
                                          location); values in
                                          meters.

TRLVL          45      52     Real        Data variable - the
                                          average of the mean
                                          tide levels of all
                                          the gauge stations
                                          that occur within a
                                          given 0.25 degree grid cell
                                          (mean tide level is
                                          a plane midway
                                          between mean low
                                          water and mean high
                                          water in 1988).
                                          Values were reckoned
                                          from chart datums
                                          (i.e., the Gulf
                                          Coast Mean Low Water
                                          Datum).

TRNUM          53      56     Integer     Data variable -
                                          number of tide gauge
                                          stations used in
                                          calculating TRAVG,
                                          TRMAX, and TRLVL for
                                          a given 0.25 degree grid
                                          cell.

WHAVG          57      64     Real        Data variable - 20-
                                          year mean wave
                                          height experienced
                                          within each 0.25 degree
                                          grid cell; values in
                                          meters.

WHMAX          65      72     Real        Data variable -
                                          maximum significant
                                          wave height for
                                          each 0.25 degree grid
                                          cell; values in
                                          meters.

WHSD           73      80     Real        Data variable -
                                          standard deviation
                                          of the 20-year mean
                                          wave height
                                          experienced within
                                          each 0.25 degree grid
                                          cell; values in
                                          meters.

Within GCGRID missing data values are identified as follows:

9999.99  -   A grid cell with real data values that is missing
data for a given data variable.

9999  -   A grid cell with integer data values that is missing
data for a given data variable.

A value of 0.0 is a valid value for all variables. For the
elevation variables 0.0 m indicates that land occurs within the
given grid cell, but the mean elevation of this land is < 1.0 m.
If the data variables in a given data set, such as elevation,
contain data and the "number" variable is set to zero (i.e.,
ELNUM, ERNUM, TRNUM, or SLYR), then the data variables for the
given 0.25 degree grid cell have been estimated.

Data Group GCRISK:

This data group contains gridded data for the seven classified
risk variables. These risk variables are classified versions of
the following original variables: mean coastal elevation,
geology, geomorphology, local subsidence trend, mean shoreline
displacement, mean tidal range, and maximum significant wave
height.

The names of the ARC/INFOTM coverage and flat ASCII files are
GCRISK.E00 (File 8) and GCRISK.ASC (File 9), respectively. A
summary of the format used in File 9 follows:

   10 READ(5,100,END=999) ID,
     1  ELR,GLR,GMR,LSR,ERR,TRR,WHR
 100 FORMAT(I5,7I4)

The variables in data group GCRISK, listed in Table 9, 
are shown as they appear in File 13.

Table 9. Variable formats for GCRISK.ASC (File 9).

                 Column
Variable name Start   End  Variable type  Variable description

ID               1     5     Integer      System variable - grid cell
                                          identifier. 

ELR              6     9     Integer      Data variable - classified
                                          version of the mean elevation
                                          variable (i.e., ELAVG). 

GLR             10    13     Integer      Data variable - classified
                                          version of the geology
                                          variable (i.e., GL).

GMR             14    17     Integer      Data variable - classified
                                          version of the
                                          geomorphology variable (i.e.,
                                          GM).

LSR             18    21     Integer      Data variable - classified
                                          version of the local
                                          subsidence trend variable
                                          (i.e., SLS).

ERR             22    25     Integer      Data variable - classified
                                          version of the mean
                                          erosion/accretion variable
                                          (i.e., ERAVG).

TRR             26    29     Integer      Data variable - classified
                                          version of the mean tide
                                          range variable (i.e.,
                                          TRAVG).

WHR             30    33     Integer      Data variable - classified
                                          version of the maximum
                                          significant wave - height
                                          variable (i.e., WHMAX).

A value of zero is used to identify missing data values within the 
grid cell for the risk variables. If several "no data" values occur 
within the same grid cell, then any calculated coastal vulnerability
index that uses these relative risk factors may not accurately 
represent the risk of the given coastal area to sea level rise or 
coastal erosion (unless some type of corrective action is taken).
Grid cells that are not in the coastal zone, or are totally ocean 
bound, have values of zero for all seven derived risk variables.

Data Group GCLINE:

This data group contains 1:2,000,000 digitized line segment for  
the 29 data variables contained within this data base 
(i.e., the 22 original and the seven relative risk data 
variables). These data variables are from the seven data sets 
and are as follows: mean, maximum, and minimum elevation, the 
number of 5' grid cells used in deriving the data values, and 
the elevation risk (i.e., the classified version of the mean 
elevation variable); geology and the geology risk (i.e., the
classified version of the geology variable; geomorphology 
and geomorphology risk (i.e., the classified version of the 
geomorphology variable); relative sea level trend, global-
trend, corrected sea level trend, local subsidence trend, 
the years of record of the gauge stations used in
calculating these values, and the local subsidence trend risk 
(i.e., the classified version of the local subsidence trend 
variable); mean, maximum, and minimum shoreline displacement, 
the number of 3', 7.5', or 15' grid cells used in deriving 
the data values, and erosion risk (i.e., the classified
version of the mean erosion/accretion variable); mean and 
maximum tidal range, mean tide level, the number of tidal 
stations used in calculating these values, and the 
tidal-range risk (i.e., the classified version of the mean 
tidal range); 20 year mean wave height, maximum significant 
wave height, the 20 year mean wave height standard deviation, 
and the wave-height risk (i.e., classified version of the 
maximum significant wave-height variable).

The names of the ARC/INFOTM coverage and flat ASCII file 
that provide these data variables are GCLINE.E00 (File 12) 
and GCLINE.ASC (File 13), respectively. File 13 is formatted 
as follows:

   10 read(5,100,end=999) id,elavg,elmax,elmin,elnum,
     1  elr,gl,glr,gm,gmr,slr,slg,slc,sls, 
     1  slyr,lsr 
      read(5,110) eravg,ermax,ermin,ernum,err,travg,
     1  trmax,trlvl,trnum,trr,whavg,whmax, 
     1  whsd,whr
 100 format(i5,3f8.2,6i4,4f8.2,2i4)
  110 format(3f8.2,2i4,3f8.2,2i4,3f8.2,i4)

The variables in data group GCLINE (File 13) are shown in 
Table 10 and are listed as they appear in the file.


Table 10. Variable formats for GCLINE.ASC (File 13).

                 Column
Variable name Start   End  Variable type  Variable description

ID               1      5     Integer     System variable - grid cell
                                          identifier.

ELAVG            6     13     Real        Data variable - mean
                                          elevation of all positive 5' by
                                          5' grid cells within a given
                                          0.25 degree grid cell; values in
                                          meters. 

ELMAX           14     21     Real        Data variable - maximum
                                          elevation of all positive 5' by
                                          5' grid cells within a given
                                          0.25 degree grid cell; values in
                                          meters.

ELMIN           22     29     Real        Data variable - minimum
                                          elevation of all positive 5' by
                                          5' grid cells within a given
                                          0.25 degree grid cell; values in
                                          meters.

ELNUM           30     33     Integer     Data variable - number of 5'
                                          by 5' grid cells used in
                                          calculating ELAVG, ELMIN,
                                          and ELMAX for a given
                                          0.25 degree grid cell.

ELR             34     37     Integer     Data variable - classified
                                          version of the mean elevation
                                          variable (i.e., ELAVG).

GL              38     41     Integer     Data variable - ordinal value 
                                          indicative of the type and
                                          resistance of the rocks within
                                          a given 0.25 degree grid cell to
                                          erosion.

GLR             42     45     Integer     Data variable - classified
                                          version of the geology 
                                          variable (i.e., GL).

GM              46     49     Integer     Data variable - ordinal value
                                          indicative of the type and
                                          susceptibility of the
                                          landforms within a given
                                          0.25 degree grid cell to inundation
                                          and erosion.

GMR             50     53     Integer     Data variable - classified
                                          version of the
                                          geomorphology variable (i.e.,
                                          GM).

SLR             54     61     Real        Data variable - relative sea
                                          level trend within a given
                                          0.25 degree grid cell; values in
                                          mm/year.

SLG             62     69     Real        Data variable - long-term
                                          geologic trend derived from
                                          14C data for each 0.25 degree grid
                                          cell; values in mm/year.

SLC             70     77     Real        Data variable - corrected sea
                                          level trend. Tide-gauge data
                                          (i.e., SLR) corrected for
                                          geologic trends (i.e., SLG)
                                          for each 0.25 degree grid cell.


----------------------------- SECOND LINE READS AS FOLLOWS -----------------


SLS              1      8     Real        Data variable - the local
                                          subsidence trend. Tide-gauge
                                          data (i.e., SLR) corrected for
                                          the regional eustatic rate of
                                          sea level rise (i.e., 1.25 
                                          mm/year).

SLYR             9     12     Integer     Data variable - years of
                                          record used in estimating the
                                          sea level trend for each 0.25 degree
                                          grid cell.

LSR             13     16     Integer     Data variable - classified
                                          version of the local
                                          subsidence trend variable
                                          (i.e., SLS).

ERAVG           17     24     Real        Data variable - mean long-
                                          term erosion trend for given
                                          0.25 degree grid cell; values in
                                          meters.

ERMAX           25     32     Real        Data variable - maximum
                                          long-term erosion trend for a
                                          given 0.25 degree grid cell; values in
                                          meters.

ERMIN           33     40     Real        Data variable - minimum
                                          long-term erosion trend for a
                                          given 0.25 degree grid cell; values in
                                          meters.

ERNUM           41     44     Integer     Data variable - number of
                                          3', 7.5', or 15' grid cells
                                          used in calculating ERAVG,
                                          ERMIN, and ERMAX for a
                                          given 0.25 degree grid cell.

ERR             45     48     Integer     Data variable - classified
                                          version of the mean
                                          erosion/accretion variable
                                          (i.e., ERAVG).

TRAVG           49     55     Real        Data variable - average of
                                          the mean tide range for all
                                          the gauge stations that occur
                                          within a given 0.25 degree grid cell
                                          (mean tide range is the
                                          difference in height between
                                          mean high water and mean
                                          low water in 1988); values in
                                          meters.

TRMAX          56      64     Real        Data variable - maximum tide
                                          range measured for all gauge
                                          stations that occurred within
                                          a given 0.25 degree grid cell in 1988
                                          (this value may be the
                                          "spring" or "diurnal" tide
                                          range, depending on
                                          geographic location); values
                                          in meters.

TRLVL          65      72     Real        Data variable - the average
                                          of the mean tide levels of all
                                          the gauge stations that occur
                                          within a given 0.25 degree grid cell
                                          (mean tide level is a plane
                                          midway between mean low
                                          water and mean high water
                                          in 1988). Values were
                                          reckoned from chart datums
                                          (i.e., the Gulf Coast Mean
                                          Low Water Datum).

TRNUM          73      76     Integer     Data variable - number of
                                          tide gauge stations used in
                                          calculating TRAVG,
                                          TRMAX, and TRLVL for a
                                          given 0.25 degree grid cell.

TRR            77      80     Integer     Data variable - classified
                                          version of the mean tide
                                          range variable (i.e.,
                                          TRAVG).


----------------------------- THIRD LINE READS AS FOLLOWS -----------------


WHAVG           1       8     Real        Data variable - 20-year mean
                                          wave height experienced
                                          within each 0.25 degree grid cell;
                                          values in meters.

WHMAX          9       16     Real        Data variable - maximum
                                          significant wave height for
                                          each 0.25 degree grid cell; values in
                                          meters.

WHSD          17       24     Real        Data variable - standard
                                          deviation of the 20-year
                                          mean wave height
                                          experienced within each 0.25 degree
                                          grid cell; values in meters.

WHR           25       28     Integer     Data variable - classified
                                          version of the maximum
                                          significant wave-height
                                          variable (i.e., WHMAX).


Within GCLINE missing data values are indicated as follows:

9999.99  -  A line segment with real data values that is missing 
            data for a given data variable.

9999  -   A line segment with integer data values that is missing data 
          for a given data variable.

0 -   A line segment with missing data values for the risk variables.

A value of 0.0 is a valid value for all variables. For the elevation 
variables 0.0 m indicates that land occurs within the given grid cell, 
but the maximum elevation of this land is < 1.0 m. If the
data variables in a given data set, such as elevation, contain data 
and the "number" variable is set to zero (i.e., ELNUM, ERNUM, TRNUM, 
or SLYR), then the data variables for the given 0.25 degree
grid cell have been estimated. 

Data Group GCPOINT:

This data group contains the point data for the stations used in 
calculating the relative sea level trend, long-term geologic-trend, 
corrected sea level trend, local subsidence trend, mean tide range,
maximum tide range, and mean tide level variables contained within 
data group GCGRID. Data include station names, station number, 
record length, latitude/longitude location, and data variable
values.

The names of the ARC/INFOTM coverage and flat ASCII file are 
GCPOINT.E00 (File 16 and GCPOINT.ASC (File 17), respectively. 
A summary of the format used for File 17 follows:

   10 READ(5,100,END=999) ID,SLLONG,SLLAT,SLR,SLG,
     1  SLC,SLS,SLYR,SLNAME
      READ(5,110) TRLONG,TRLAT,TRAVG,TRMAX,TRLVL,
     1  TRID,TRNAME
 100 FORMAT(I5,6F8.2,I4,A38)
 110 FORMAT(5F8.2,I5,A45)

The variables listed in Table 11 are listed as they appear in 
data group GCPOINT (File 17).

Table 11. Variable formats for GCPOINT.ASC (File 17).

                 Column
Variable name Start   End  Variable type  Variable description

ID               1      5    Integer      System variable - Point
                                          identification number.

SLLONG           6     13    Real         Data variable - longitude of
                                          the tide- gauge station used
                                          in determining the sea level
                                          trends.

SLLAT           14     21    Real         Data variable - latitude of
                                          the tide- gauge station used
                                          in determining the sea level
                                          trends.

SLR             22     29    Real         Data variable - relative sea
                                          level trend measured for each
                                          tide-gauge station; values are
                                          expressed in mm/year.

SLG             30     37    Real         Data variable - long-term
                                          geologic trend derived from
                                          C14 data; values are expressed
                                          in mm/year.

SLC             38     45    Real         Data variable - corrected sea
                                          level trend. Tide-gauge data
                                          (i.e., SLR) corrected for
                                          long-term geologic-trends
                                          (i.e., SLG); values are
                                          expressed in mm/year.

SLS             46     53    Real         Data variable - local
                                          subsidence trend. Relative
                                          sea level trend corrected for
                                          the regional eustatic rate of
                                          sea level rise (i.e., 1.25
                                          mm/year).

SLYR            54     57    Integer      Data variable - years of
                                          record of the tide gauge
                                          station used in determining
                                          the sea level trends.

SLNAME          58     81    Char         Data variable - name of the
                                          tide gauge used for
                                          determining the sea level
                                          trends.


----------------- SECOND LINE READS AS FOLLOWS --------------------


TRLONG          1       8    Real         Data variable - longitude of a
                                          tide-gauge station used for
                                          determining the tide range
                                          ariables.

TRLAT           9      16    Real         Data variable - latitude of a
                                          tide-gauge station used for
                                          determining the tide range
                                          variables.

TRAVG          17      24    Real         Data variable - difference
                                          between mean high water
                                          and mean low water for
                                          1988; values in meters.

TRMAX          25      32    Real         Data variable - maximum tide
                                          range, maximum measured
                                          range for the gauge station in
                                          1988 (this value may be the
                                          "spring" or "diurnal" tide
                                          range, depending on
                                          geographic location); values
                                          in meters.

TRLVL          33      40    Real         Data variable - mean tide
                                          level, a plane midway
                                          between mean low water and
                                          mean high water in 1988.
                                          Values are reckoned from
                                          chart datums (i.e., the Gulf
                                          Coast Mean Low Water
                                          Datum).

TRID           41      44    Integer      Data variable - station
                                          number (used in the 1988
                                          Tide Tables) of a tide-gauge
                                          station.

TRNAME         45      81    Char         Data variable - name of a
                                          tide-gauge station (from the
                                          1992 Tide Tables).


Within this data file, GCPOINT, missing data values are indicated 
with one of the following values:

   0.0 or 0 - A tide range or sea-level station that has not been
              assigned data for the variable in question.

In this data group the sea level variables and tide range variables 
are mutually exclusive (i.e., if tide-range data are present, then the 
sea-level data are missing or vice versa).

Data Group GCOAST:

Auxiliary data group GCOAST (Files 20 and 21) contains a 1:2,000,000 
digitized coastline of the U.S. Gulf Coast. Data in this coverage were 
extracted from a digitized map of the United States (originally compiled 
by the U.S. Geological Survey). This coastline may be overlaid onto any of
the three data groups previously discussed to provide locational 
information when plotting any or all of the data variables.

Unlike the other data groups within this data base, this coverage 
contains line segments (or arcs) that describe the Gulf Coast. The 
coastline provided has no attribute values associated with the
line segments. However, such overlay commands as UNION, INTERSECT, and 
IDENTITY in ARC/INFOTM (or other GISs) may be used to transfer the 
gridded data values to the coastal segments, thus simplifying the 
interpretation of any derived indices.

The name of the ARC/INFOTM coverage where the coastline resides is 
GCOAST.E00 (File 20), and the flat ASCII data file with this same 
information is in GCOAST.ASC (File 21). Since this file is line based, 
the data values in GCOAST.ASC contain the line segment name, and a listing
of the points that describe each line, for all 934 line segments that 
define the Gulf Coast.

The flat ASCII version of this file contains a listing of the line 
segments (or arcs) that describe the coast. An example of the format for 
this file is shown in Table 12.

Table 12. Sample of the vector format used for GCOAST.ASC (File 21).

   Name, Number of points
   - Data points           Data interpretation

   "   1", -14             -Vector 1 uses 14 points to describe the line
   -88.0000,30.7848        -Start at -88.00 W. Longitude, 30.78  N. Latitude
   -87.9967,30.7839
   -87.9915,30.7806
   -87.9883,30.7806
   -87.9856,30.7806
   -87.9825,30.7755
   -87.9821,30.7705
   -87.9821,30.7677
   -87.9827,30.7645
   -87.9843,30.7627
   -87.9876,30.7605
   -87.9898,30.7573
   -87.9946,30.7551
   -88.0000,30.7529
   "  2", -35              -Vector 2 uses 35 points to describe the line
   -87.9361,30.7515        -Start at 87.94 W Longitude, 30.75 N Latitude
   -87.9355,30.7556
   ...                     -Continued