Where lft, rgt, top, bot refer to the left, right, top and bottom. arc is obviously the ARChive format. siz= is the "Size" in megabytes of the file mdf = metadata format key =??? RC = Some kind of UID? Can be left blank, but must be submitted zun = Z Units (must be meters?) csx= X grid spacing csy = Y grid spacing bnd = ? bndnum = ?
All fields seem to be required, but have some flexibility as far as the input data (don't know if this changes the output data)