Alfred McEwen's notes on the original mosaics....
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		NEW CONTROLLED MAP OF IO

     A new global mosaic of Io has been completed, tied to the
control net derived by Robert Gaskell of JPL (Gaskell et al.,
1989; Gaskell and Synnott, 1989).  The self-consistency of the
solution is excellent, as shown by the agreement of the overlap
regions of reprojected images.  The fact that Gaskell et al.'s
triaxial solution matches the equilibrium prediction is also
encouraging.  The lat-lon positions of features on previous Io
maps, both USGS map sheets and the color mosaic (McEwen, 1988),
are off by up to at least 5 degrees; such errors may matter to
some of the recent Earth-based observations. (Thanks to John
Spencer for bringing this to my attention.)  I'm sure the new map
is accurate to within less than 1 degree everywhere except the
polar regions (very oblique or no data) and the lowest-resolution
coverage near long 50 degrees (probably good to within 2
degrees).  Examples of how far off features are on USGS Map
I-1491: Loki is 0.5 deg too far west and south, Masubi is 1 deg
too far north and 3 deg too far west, Babbar Patera is 0.5 deg
too far south, and a lava flow that may correspond to
"Kanehekili" is 0.5 deg too far north and 5 deg too far west.

     This new map is available in digital format, and can be
copied to your default directory (VAX/VMS) by
	COPY ASTROG::WORK3:[AMCEWEN]IOBASE.PIC *
IOBASE is in Simple Cylindrical projection, 0.1 degrees/pixel,
lat. -90 to 90, long -180 to 180.  The data is 8-bit (byte) and
has been given a large-scale high-pass filter to normalize
limb-darkening variations and differences due to bandpass.  The
mosaic consists of narrow-angle clear and blue filter and
wide-angle clear filter images, providing the best global
resolution up to 3.4 km/pixel from Voyager 1 images.  A separate
Voyager 2 mosaic will follow some day.  Higher-res Voyager 1
images over the sub-Jove/southern latitudes have been tied to
this base and will be mosaicked separately.)
     Also available on ASTROG::WORK3:[AMCEWEN] are:
IOBASEG.PIC  IOBASE with a 10 x 10 deg lat-lon grid overlay.
IO0.PIC  Orthographoc projection, 3 km/pixel, center lat 0, lon 0
IO90.PIC  Orth, centered on lat 0, lon 90
IO180.PIC  Orth, centered on lat 0, lon 180
IO270.PIC  Orth, centered on lat 0, lon 270
IOORTH.PIC  Mosaic of 4 Orth views, with 10 x 10 lat-lon
	    overlays.
     I will send prints of the above if requested.
						Alfred McEwen
						USGS/Flagstaff
						(602) 556-7194


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John Spencer's notes on the FITS versions of the mosaics:

iobase.jpg            Compressed FITS-format Voyager image mosaic of Io, 
                      using the latest Io control network (accurate to
                      < 1 degree).  Not photometric: good for positions
                      only.  Courtesy Alfred McEwen.
                      3600 x 1800 byte array with 0.1 x 0.1 degree resolution,
                      x value goes from 179.95 to -179.95 degrees longitude,
                      y value from 89.95 to -89.95 degrees in latitude.

iobasesmall.jpg       Like iobase.jpg    but 1800 x 900 with 0.2 x 0.2 degree
                      resolution, from 179.9 to -179.9 in longitude, 89.9
                      to -89.9 in latitude.

iobasetiny.jpg        Like iobase.jpg    but 720 x 360 with 0.5 x 0.5 degree
                      resolution, from 179.75 to -179.75 in longitude, 89.75
                      to -89.75 in latitude.

iobaseg.jpg           Like iobase.jpg    but with a 10 x 10 degree latitude/
                      longitude grid superimposed.

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