MASTER(1) TeraScan Command MASTER(1)
NAME
master, master2, master4 - generates a base map and projec-
tion for a user specified area.
SYNOPSIS
master [ _p_a_r_a_m_e_t_e_r=_v_a_l_u_e ... ] [ _o_u_t_p_u_t_f_i_l_e ]
master2 [ _p_a_r_a_m_e_t_e_r=_v_a_l_u_e ... ] [ _o_u_t_p_u_t_f_i_l_e ]
master4 [ _p_a_r_a_m_e_t_e_r=_v_a_l_u_e ... ] [ _o_u_t_p_u_t_f_i_l_e ]
Parameters for master are projection, center_lat,
center_lon, num_lines, num_samples, pixel_width,
pixel_height, standard_lat, rotate_angle, move_center,
new_center_lat, new_center_lon.
Parameters for master2 are projection, min_lat, max_lat,
min_lon, max_lon, square_aspect, num_lines, num_samples,
estim_center, center_lat, center_lon, standard_lat,
rotate_angle.
Parameters for master4 are projection, estim_center,
center_lat, center_lon, rotate_angle, standard_lat,
num_lines, num_samples, up_left_lat, up_left_lon,
low_left_lat, low_left_lon, up_right_lat, up_right_lon,
low_right_lat, low_right_lon.
DESCRIPTION
These functions generate a (master) dataset containing
attributes that parameterize an earth transform. This
transform relates line and sample coordinates to latitude
and longitude coordinates for a user defined geographical
region using a user specified map projection. master
defines the region by the center latitude and longitude, and
the pixel size at the center. master2 defines the region
using a bounding latitude/longitude box. master4 defines
the region using corner (lat/lon) coordinates.
Master datasets are used by a variety of ingest functions
such as hrptin and rtdin to limit data extraction to only
the rectangular subset of sensor data that intersects the
geographical area specified by a master dataset.
Master datasets are most often used to interpolate data in
sensor coordinates onto the region defined by the master
dataset. This is done by using registration functions such
as fastreg(1). fastreg takes all of the data within an
input dataset and interpolates that data onto the grid
defined by the master dataset. Data falling outside the
master dataset are discarded by fastreg.
Master datasets can also be used by passcover and catcover
to determine whether a satellite pass intersects a master
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MASTER(1) TeraScan Command MASTER(1)
dataset.
Master datasets contain two dimensions _l_i_n_e and _s_a_m_p_l_e, plus
attributes that describe the map projection. Master
datasets also contain a null (empty) variable called master
with line and sample dimensions. This variable can be
displayed to create and blank background overwhich various
overlays (geopolitical boundaries, lat/lon grids) can be
drawn.
PARAMETERS
projection
Name of the map projection. Valid responses are stere-
ographic, rectangular, orthographic, polarstereo,
equidist_azim, mercator, utm, polyconic, lambert_azim,
lambert_conic, and albers_conic. There is no default.
polarstereo is not supported by master2.
polarstereo, lambert_conic, and albers_conic projec-
tions are based on a geodetic (elliptic) earth. All
other projections are based on a spherical earth.
These map projections are defined in the publication
entitled Map Projections used by the U.S. Geological
Survey, Bulletin 1532 by John P. Snyder.
For minimal distortion, rectangular and mercator pro-
jections should not be used for maps centered near the
poles.
estim_center
Option to estimate the mathematical projection center
in master2 and master4. Valid responses are yes and
no. The default is yes.
center_lat, center_lon
Center (lat, lon) coordinates used for the mathematical
definition of the map projection. They may not appear
at the center of the master dataset, however, depending
on other parameters. See formats(7) for valid ways to
specify latitude and longitude. There is no default
value.
[ Exception. When projection=polarstereo, the
mathematical center latitude is taken to be the nearest
pole to the user specified center_lat. The master data
center is _m_o_v_e_d to the user specified center_lat and
center_lon by adjusting the master dataset's affine
transform attribute. ]
center_lat and center_lon are not used by master2 or
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MASTER(1) TeraScan Command MASTER(1)
master4 unless estim_center=no.
min_lat, max_lat
Latitude limits used by master2. See formats(7) for
valid ways to specify latitude. min_lat must be less
than max_lat. There is no default.
min_lon, max_lon
Longitude limits used by master2. See formats(7) for
valid ways to specify longitude. min_lat is the left-
most longitude; max_lon is the rightmost longitude.
There is no default.
up_left_lat, up_left_lon, up_right_lat, up_right_lon
Upper left corner and upper right corner (lat, lon)
coordinates used by master4. They apply to the center
of the corner pixels, not to the outer corner. See
formats(7) for valid ways to specify latitude and long-
itude. There are no defaults.
low_left_lat, low_left_lon, low_right_lat, low_right_lon
Lower left corner and lower right corner (lat, lon)
coordinates used by master4. They apply to the center
of the corner pixels, not to the outer corner. See
formats(7) for valid ways to specify latitude and long-
itude. There are no defaults.
square_aspect
Option in master2 to make pixel width the same as pixel
height. If square_aspect=yes, only num_samples is user
specified; num_lines is computed using the lat/lon lim-
its and num_samples. In the case, the pixel height and
width near the center of the master dataset will rarely
be a round number.
If square_aspect=no, chances are that the pixel aspect
near the center of the master dataset will not be one.
num_lines, num_samples
Height and width of the master dataset in pixels.
There is no default. In the case of master2, if
square_aspect=yes, only num_samples is user specified;
num_lines is computed.
pixel_width, pixel_height
Pixel width and height in kilometers, at the projection
center, before any rotation. Note, for projections
polarstereo, lambert_conic and albers_conic, pixel size
is enforced along the standard parallels, not at the
center.
The valid range for pixel_width and pixel_height is
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MASTER(1) TeraScan Command MASTER(1)
[.001, 1000.]. The default is 1.1132 km = 0.01*(degree
of latitude). These parameters are used only by mas-
ter.
standard_lat
If projection=polarstereo, then standard_lat is the
standard parallel of the projection, e.g., the latitude
at which the plane intersects the earth. The default
is 70.
If the projection is lamber_conic or albers_conic, then
standard_lat is the distance from the center_latitude
to the standard parallels, e.g., the latitudes where
the cone intersects the earth. The default is 5.
Otherwise, standard_lat does not apply. standard_lat
is not used by master2 or master4 unless
estim_center=no.
rotate_angle
This parameter allows the north end of the master
dataset to be rotated clockwise through this angle.
Normally, line 1 is the northern most line. The valid
range is [-180 to 180]. The default is 0.
rotate_angle is not used by master2 or master4 unless
estim_center=no.
move_center, new_center_lat, new_center_lon
Option in master to move the master dataset center away
from the mathematical projection center.
new_center_lat and new_center_lon are used only if
move_center=yes. See formats(7) for ways to specify
latitude and longitude.
When projection=polarstereo, move_center is not used.
The center of the master dataset is _m_o_v_e_d to the user
specified center_lat and center_lon. See the Exception
noted above.
EXAMPLES
This example illustrates the building of a base map located
in the vicinity of the Hawaiian Islands. The base map
defines an approximately square area, 1024x1.1132 kilometers
on a side.
[1] % master
output file : char(255) ? [Master]
projection : char( 13) ? rect
center_lat : char( 15) ? 21 N
center_lon : char( 15) ? 157 W
num_lines : int ? 1024
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MASTER(1) TeraScan Command MASTER(1)
num_samples : int ? 1024
pixel_width : real ? [1.1132]
pixel_height : real ? [1.1132]
rotate_angle : real ? [0]
move_center : char( 3) ? [yes]
The next two examples illustrate the usage of master2. The
master datasets are bounded by the rectangle [30n, 50n] X
[120w, 90w]. Both methods for controlling pixel
width/height aspect ratio are shown.
% master2
output file : char(255) ? [Master]
projection : char( 13) ? stereo
min_lat : char( 15) ? 30 n
max_lat : char( 15) ? 50 n
min_lon : char( 15) ? 120 w
max_lon : char( 15) ? 90 w
square_aspect : char( 3) ? [yes]
num_samples : int ? 1000
master2: 836 lines, 1000 samples,
2.91724 km pixel height, 2.91724 km pixel width
%
% master2
output file : char(255) ? [Master]
projection : char( 13) ? stereo
min_lat : char( 15) ? 30 n
max_lat : char( 15) ? 50 n
min_lon : char( 15) ? 120 w
max_lon : char( 15) ? 90 w
square_aspect : char( 3) ? [yes] n
num_lines : int ? 850
num_samples : int ? 1000
master2: 850 lines, 1000 samples,
2.86643 km pixel height, 2.91724 km pixel width
The last example illustrates the usage of master4. Note,
that because the projection is rectangular, and the corners
are _p_e_r_f_e_c_t, the pixel errors are extremely small. This
would not normally be the case with other projections.
% master4
output file : char(255) ? [Master]
projection : char( 13) ? [utm] rect
estim_center : char( 3) ? [yes]
num_lines : int ? 1024
num_samples : int ? 1024
up_left_lat : char( 15) ? 40n
up_left_lon : char( 15) ? 140w
low_left_lat : char( 15) ? 30n
low_left_lon : char( 15) ? 140w
up_right_lat : char( 15) ? 45n
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MASTER(1) TeraScan Command MASTER(1)
up_right_lon : char( 15) ? 120w
low_right_lat : char( 15) ? 35n
low_right_lon : char( 15) ? 120w
Pixel errors: max = 5.08423e-13, mean = 4.21531e-13, std dev = 1.97176e-13
%
SEE ALSO
etx(7), formats(7), fastreg(1).
NOTES
master4 uses least squares to determine the _b_e_s_t values for
the et_affine attribute. Pixel height, width, and the angle
of rotation are encoded within this attribute. The affine
transform is discussed in the etx(7) man page.
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