Level 2 Help for GTLIST

A standalone GeoTIFF label does not have to have a VICAR image.
So, to help the user work with the mapping, a hypothetical image
is generated.   This parameter can give the size of the hypothetical
image.  If a VICAR image is present, this parameter is ignored.

A standalone GeoTIFF label does not have to have a VICAR image.
So, to help the user work with the mapping, a hypothetical image
is generated.   This parameter can give the size of the hypothetical
image.  If a VICAR image is present, this parameter is ignored.

Inputting this value allows the list program to calculate the
map scale fraction.  Also needed is the number of inches subtended
by the map on paper or screen.  Use the horizontal direction if
there is a difference with the vertical.  Also, use the middle of
the map to determine this value.  

Note that the map unit may be "meters", but in the middle of a map,
a map unit meter may be something like .978 meters.  Mapping
software is a good source of this value if exactness is desired.

Inputting this value allows the list program to calculate the
map scale fraction.  Also needed is the size of the map unit in
meters (see MAPUNITM parameter).  Use the horizontal direction if
there is a difference with the vertical.

GTLIST reads the GeoTIFF label and the VICAR NL,NS parameters.  The
printout is based on these.  Note that the GeoTIFF image coordinate
system will differ systematically from the VICAR image coordinate
(line,sample) system by a half a pixel or a whole pixel (depending 
on whether the GeoTIFF file is "area" format or "post" format.  An
example of a "post" formatted file is DMA DTED -- there is an
elevation reading exactly at the initial lon-lat.

In addition, rotation is explained.  Rotation refers to the order
of pixels in the file.  The eight possible rotation are (here, pixel
value represents the order of data in the file):

   369    123    741    987
0: 258 1: 456 2: 852 3: 654
   147    789    963    321

   963    789    147    321
4: 852 5: 456 6: 258 7: 654
   741    123    369    987

Rotation 1 is the VICAR standard rotation.  It is used also by
systems such as LAS, IDIMS, LARSYS, ERDAS, I2S, etc. and was
adopted by LANDSAT, SPOT, and all of the planetary probes.
It is also produced by frame grabbers since it is the
ordering of a TV scan.  Rotation 0 is the USGS standard and is
used, for example, for DMA DTED.

The fact that an image is "rotated" is due to the different ways
that line-sample ordering can represent a geographic east-north
coordinate system.


The transitions among these rotations are given by the
following table:

	   no flip              flip

rotate->0  90 180 270      0  90 180 270

   0)   0   3   2   1      4   5   6   7
   1)   1   0   3   2      5   6   7   4
   2)   2   1   0   3      6   7   4   5
   3)   3   2   1   0      7   4   5   6
   4)   4   5   6   7      0   3   2   1
   5)   5   6   7   4      1   0   3   2
   6)   6   7   4   5      2   1   0   3
   7)   7   4   5   6      3   2   1   0


VICAR can process images with any rotation (basically by ignoring
the fact that rotation means anything).  The exception would be
for programs that combine images such as F2, OVERLAY, APPEND, MSS,
FASTMOS, etc.  These correctly operate only when the images have
the same rotation.