Level 2 Help for MAPTRAN

STRING-input datasets.
First input:
  The picture to be projected and placed into the output.
  This picture must have map projection labels compatible with those
  created by MAP3.
Second input:
  If the MOSAIC keyword is used then:
  This picture is used for its label,sizefield, and contents.
  The label defines the output projection type.
  The output will be a mosaic of this file AND the projected first input.
  otherwise:
  This picture is used merely for its label and for the NL and NS values.
  The image itself is ignored. The label defines the output projection type.
  This picture must have map projection labels compatible with those
  created by MAP3.

STRING-output dataset.
This is the projected version of the first input file. Its projection 
label will be copied from the second input file.

Output picture number of lines. If NL is not specified it defaults to
the size of the second input file.

Output picture number of samples. If NS is not specified it defaults to
the size of the second input file.

Output picture number of bands. If NB is not specified it defaults to
the size of the first input file.  (Note that this differs from the
defaults for NL and NS!)

Output picture starting band & number of bands. The default is to use
NB of the first input file.  

Grid spacing in pixels for the output file. 
A fine grid is overlayed on the output file and the exact mapping is 
computed at each grid intersection. Pixels within the grid are 
interpolated. INC specifies the smallest grid desired. If INC is too
small MAPTRAN will increase it until the grid can reside in memory.

In the case where individual pixels are being projected using the 
precise mapping projection equations (versus polynomial mapping)
the on-planet corners of the INC by INC area will fall either on or
off the input block of data lines. In case the points fall more than
RANGE pixels from the data block then this INC by INC area is bypassed
on the first pass through the input image. We hope to save time by
avoiding needless computations for pixels mapping outside the
input data block. If a second pass is needed this restriction is
lifted.

Used only in the MOSAIC mode.
Thresh specifies the dn value above which the projected image has
precedence over the second input file during mosaicking of the two files.
Default is zero, ie: any projected dn which is zero or less will be
ignored in favor of the dn in input number 2.

Specifies a DN threshold used only in interpolation mode. If, when
interpolating a dn value in the input file, one or more of the four
neighbors is less than or equal to DNINTER it will not be used
in the interpolation.
Several combinations of input dn values can occur.
Cases:
If 4 input neighbors are > dninter then bilinear interpolation is done.
If 3 input neighbors are > dninter the fourth is extrapolated and then
   interpolation is done.
If 2 input neighbors are > dninter the output pixel is determined from
   a linear weighting of the 2 good pixels.
If 1 input neighbor is > dninter it is copied to the output.
If all the input neighbors are <= dninter the output is determined from
   the nearest neighbor.

Specifies that no interpolation between pixels is desired.  
The output pixel will come from the nearest neighbor in the input.
Default is to interpolate.
See DNINTER keyword for interpolation modes.

This is a number that is used by Maptran to mark the location of output 
pixels whose DN values have not yet been determined. The default is -99999. 
If you have input DN's that happen to have this value (in the first input 
file) they will be reset to one dn higher. Thus -99999 would become -99998.
(Obviously, this could only happen if the input file were in REAL format.)
It is assumed that this change is insignificant, but if it should be, then
CODE should be set to some number outside of the range of the input data.

Normally Maptran checks for wraparound in the sample direction for three
projections. These are: Mercator, Normal Cylindrical, and Simple Cylindrical.
Nocheck deactivates this checking.