12. Apprendix D: Unavailable Optional Arguments

There are a number of "unavailable" optional arguments. These are in the optional argument table, but the validation routine returns a NOT_IMPLEMENTED error. They are:

• NLINES: input, integer
  Indicates the number of lines to be accessed in a single operation. Defaults to 1.
• SLICE1: input, integer
  Indicates the starting pixel in the first dimension of the image. Thus this argument may refer to the LINE, SAMP, or BAND dimension depending on the file organization. It defaults to a starting value of 1and increments per read by 1. (NOT YET AVAILABLE)
• SLICE2: input, integer
  As in SLICE1 but for the second file dimension. It defaults to 1 and remains at 1 unless explicitly changed. (NOT YET AVAILABLE)
• SLICE3: input, integer
  As in SLICE2 but for the third file dimension. (NOT YET AVAILABLE)
• NSLICE1: input, integer
  Indicates the number of pixels to be accessed in the first dimension of the file. Defaults to the length of the first file dimension. (NOT YET AVAILABLE)
• NSLICE2: input, integer
  As in NSLICE1 except for the second file dimension. Defaults, however, to 1. (NOT YET AVAILABLE)
• NSLICE3: input, integer
  As in NSLICE2 except for the third file dimension. (NOT YET AVAILABLE)
• U_N4: input, integer
  Indicate that the Executive is to ensure that the output file will have its fourth dimension specified by this value This argument is useful for the program which does not care about the file organization, and simply wants to deal with records and pixels.
• N4: output, integer
  The number of pixels in the fourth dimension of the image. The value returned refers to the physical dimensions of the file and is independent of file organization.

See the table in $V2TOP/rtl/source/global.c for details.

There are more of these arguments that were (are?) planned for but were never implemented. The SLICE things should give you access to dimensions 1,2,3,(4) regardless of the order (BSQ/BIL/BIP). Right now, you have to jump through some hoops for order-independent reading. And there were apparently plans to have 4-dimensional files, but they were never realized. NLINES was for multi-line reads (e.g. read a tile), which would be quite useful but has not been implemented either.