QUOTE (Bill Harris @ Mar 29 2006, 01:34 PM)
Why not _slightly below right_ (ie, E 9.5deg S) since the angle is clockwise?
...
Not to be argumentative, but this has puzzled me for a long while.
I'm sorry, you're right -- and it is confusing
I think it's because the angles are relative to the
original image's coordinate system, not the map-projected image's coordinate system. North is obviously straight up in the latter.
Also, if you look at the full ancillary data table, there's this flag that isn't reflected on the website:
OBJECT = COLUMN
NAME = USAGE_NOTE
COLUMN_NUMBER = 40
DATA_TYPE = CHARACTER
START_BYTE = 346
BYTES = 1
FORMAT = "A1"
DESCRIPTION = "Because of the MOC's line-scan nature, depending on the
orientation and sense of rotation of the spacecraft and the optical
inversion properties of the camera system involved, MOC images can
either be normal or flipped left-for-right (independent of whether the
image is north up or south up.) This flag will be 'F' if the image
should be flipped left-to-right, and 'N' if it is already in normal
form."
END_OBJECT = COLUMN
OBJECT = COLUMN
NAME = NORTH_AZIMUTH
COLUMN_NUMBER = 41
DATA_TYPE = ASCII_REAL
START_BYTE = 349
BYTES = 6
FORMAT = "F6.2"
NOT_APPLICABLE_CONSTANT = 0.0
DESCRIPTION = "The angle in degrees clockwise from the reference axis
of the image (a line from the center to the right edge of the image)
to the direction to the north pole of the target body. If the
USAGE_NOTE described previously is 'F', the image should be flipped
prior to applying this angle."
END_OBJECT = COLUMN
After 1/1/1998 they started flying MGS "backwards"; prior to that there would be another flip required. I'm pretty sure that all mapping NAs are "N" though.