help project

PROJECT <COVER | GRID | FILE> <input> <output> {projection_file}
        {NEAREST | BILINEAR | CUBIC}
 
projects coordinates between two map projections.
 
arguments
 
<COVER | GRID | FILE> - specifies the source for coordinate input:
 
COVER - projects coordinates in a coverage.
 
GRID - projects coordinates in a grid.
 
FILE - projects coordinates in a file.
 
<input> - the coverage, file, or grid whose coordinates are to be projected.
 
<output> - the output coverage, file, or grid whose coordinates have been
projected into the new coordinate system.  This file or grid cannot already
exist.
 
{projection_file} - the name of a text file defining the input and output
projections.  If no {projection_file} is entered, then you will be prompted by
PROJECT to enter the input and output projections using subcommands.
 
{NEAREST | BILINEAR | CUBIC} - the resampling algorithm to be used when
projecting a grid.
 
NEAREST - nearest neighbor assignment.  This is the default.
 
BILINEAR - bilinear interpolation.
 
CUBIC - cubic convolution.
 
notes
 
A coverage can contain an explicit definition of the coordinate system
in which it is stored.  This can be created using PROJECTDEFINE or added from
another data set using PROJECTCOPY.  If not defined, the projection will be
listed as UNKNOWN.
 
Output projection information can be specified using PROJECT subcommands, a
{projection_file}, or read from an empty output coverage.  The
{projection_file} must contain both input and output projection definitions.
Use of a projection {projection_file} will override any projection information
stored in the PRJ file.
 
When projecting a coverage, the <output> can be an existing, empty coverage.
The coordinates of the <input> will then be projected into the coordinate
system defined by the PRJ file of the <output>.
 
If any error is made while you are interactively entering subcommands following
INPUT or OUTPUT, you must reenter all of the INPUT or OUTPUT commands.
Interactive entry of INPUT projection information is not necessary, nor
possible, if the projection is already defined by the input PRJ file or the
input data set.
 
The NEAREST option, which performs a nearest neighbor assignment, is the
fastest of the three interpolation methods.  It is primarily used for
categorical data such as a land use classification, since it will not change
the values of the cells.
 
The BILINEAR and CUBIC option (bilinear interpolation and cubic convolution,
respectively) determine the new value of a cell based upon a weighted distance
average of surrounding cells.  These are most appropriate for continuous data
and may cause some smoothing.  It is not recommended that BILINEAR or CUBIC be
used with categorical data, since the cell values may be altered.
 
Depending on the input and output projection definitions, an arc in the input
coverage may have to be clipped into more than one segment when the output
coverage is being generated.  This will occur whenever an arc encounters the
horizon line or crosses the line of longitude opposite the central meridian.
You will receive the following message:
 
Some coverage features were clipped or deleted.
 
Whenever a vertex is encountered that cannot be projected, it will be
interpreted as the end of an arc, and the partially projected arc will be
written to the output.  It is possible for an arc to be split into several arcs
if subsequent vertices are encountered that can be projected.  In this case,
the output retains the original IDs so that attributes can be relinked.
 
PROJECT only copies feature attribute tables from the input coverage to the
output coverage.  Note that due to the clipping that may occur, PROJECT may not
maintain feature topology.  For example, polygons located along an edge may no
longer close if an entire feature has been clipped.  After PROJECT has finished
processing, you may need to relink attributes, and use existing ARC/INFO tools
to rebuild topology and close boundary polygons.  A feature can be deleted from
a coverage but its attributes will remain in the cover.PAT until you BUILD or
CLEAN.  (The PROJECT command does not rebuild topology.)
 
If a coverage is stored in latitude-longitude coordinates, you may wish to
densify two-point arcs before projecting them into a planar coordinate system.
Adding vertices allows features to be curvilinear.  Vertices can be added to
any coverage using the ARC command DENSIFYARC or the ARCEDIT command DENSIFY.
Alternatively, vertices can be added as part of the input projection definition
using the DENSIFY subcommand before the arcs are projected.
 
Annotation placement is projected but cannot be properly scaled or rotated.
 
CLARKE 1866 is used as the default spheroid if it is not inherent to the
projection such as NEWZEALAND_GRID, unless another is specified using the
SPHEROID subcommand.
 
Coverage tolerance values are scaled by PROJECT.  However, processing a
coverage using the new, scaled tolerances in the new projection may cause
widely varying results since the shape and size of features will change between
projections.
 
The cells of a grid will always be square and of equal area, in map coordinate
space, although the shape and area a cell represents on the surface of the
Earth will never be constant across a grid.  This is because no map projection
can preserve both shape and area simultaneously.
 
The area represented by the cells will vary across the grid.  Therefore, the
output cell size and the number of rows and columns may change.
 
The cell size of the output grid is determined by the projected cell size at
the center of the output grid.  This is usually also the intersection of the
central meridian and latitude of true scale, and is therefore the area of least
distortion.
 
At Rev. 6.1 two new projections were added.  They are the Rectified Skewed
Orthomorphic and Cassini.
