STN--30p Data Structures

The global Simulated Topological Network at 30-minute spatial resolution
(STN--30p) represents rivers as a set of spatial and tabular data
layers derived from a 30-minute flow-direction grid. These data layers
are available as ARC/INFO coverages and ASCII interchange files.
The ARC/INFO coverages are located in the file stn30-5_12.tgz, while the
ASCII files are in stn30-5_12.zip.

 The ARC/INFO coverages are:

g_basin        -    Basin grid with basin attributes
g_celllength   -    Grid cell length [km] grid
g_cumularea    -    Upstream catchment area [km^2] grid
g_distmouth    -    Distance [km] to mouth of river defined as the
                    confluence with equal or higher order stream
g_distocean    -    Distance [km] to the outlet of river basins
g_network      -    Flow-direction grid
g_order        -    Strahler stream order grid
c_basin        -    Basin polygon coverage with the same
                    basin attributes as the basin grid
c_network      -    Arc/point coverage representing river segments and
                    basin mouthes


g_basin grid, c_basin polygons and c_network points have the following
STN--30p derived attributes additional to the default ARC/INFO attributes:

BASINNAME       -    Basin Name (GHAASBasin#### or
                     real basin name from GEMS/GLORI)
BASINORDER      -    Strahler stream order at mouth
COLOR           -    Optimized color (7 - 11) to display basins
BASINLENGTH     -    Mainstem length [km]
BASINAREA       -    Basin area [km^2]
CONTINENTNAME   -    Continent name
SEANAME         -    Name of the recipient sea
OCEANNAME       -    Name of the recipient ocean


The flow direction grid is given as the standard ARC/INFO representation
of the 8 flow direction grid using the following encoding scheme:

+---+----+-----+
|32 | 64 | 128 |
+---+----+-----+
|16 |    |  1  |
+---+----+-----+
|8  | 4  |  2  |
+---+----+-----+


c_network arc/line coverage has the following arc attributes besides
the point attributes listed before:

BASINNAME        -    Basin name
ORDER            -    Strahler stream order
BASINID          -    Integer basin identifier
BASINCELLS       -    Number of 30-minute cells upstream
TRAVEL           -    Number of cells downstream
CELLAREA         -    Cell area [km^2]
SUBBASINLENGTH   -    Mainstem length [km] upstream
SUBBASINAREA     -    Upstream area [km^2]
DISTTOMOUTH      -    Distance [km] to river mouth defined as
                      confluence with equal or higher order stream
DISTTOOCEAN      -    Distance [km] to the outlet of river basins
CELLLENGTH       -    Length [km] of 30 minute river segment


The ASCII data are organized in the ./ascii directory similarly to
the ARC/INFO coverages:

basin.grd        -   Basin grid with basin attributes
celllength.grd   -   Grid cell length [km] grid
cumularea.grd    -   Upstream catchment area [km^{2}] grid
distmouth.grd    -   Distance [km] to river mouth defined as
                     confluence with equal or higher order stream
distocean.grd    -   Distance [km] to the outlet of river basins
network.grd      -   Flow-direction grid
order.grd        -   Strahler stream order grid
basins.txt       -   Basin attribute table
cells.txt        -   Cell attribute table


The grids were exported as ARC/INFO ASCII grid, which has a six line
header followed by the actual cell values row by row:

ncols 720

nrows 300

xllcorner -180

yllcorner -60

cellsize 0.5

NODATA_value -9999

where

ncols          -   number of columns
nrows          -   number of rows
xllcorner      -   horizontal coordinate of the lower left corner
yllcorner      -   vertical coordinate of the lower left corner
cellsize       -   cell size
NODATA_value   -   missing data value


The attribute tables are tab-delimited, strings in quotes and the first
line contains field names.