| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This digital image map of Mars is a cartographic extension of a
previously released set of CD volumes containing individual
Viking Orbiter Images (PDS volumes VO_1001, VO_1002, etc.).
The data in the latter are pristine, in the sense that they
were processed only to the extent required to view them as
images. They contain the artifacts and the radiometric,
geometric, and photometric characteristics of the raw data
transmitted by the spacecraft. This new volume set, on the
other hand, contains cartographic compilations made by
processing the raw images to reduce radiometric and geometric
distortions and to form geodetically controlled Mosaicked
Digital Image Models (MDIMs). (Because the photometric
processing used in this MDIM was oversimplified, quantitative
radiometric analysis on this data is not possible.) It also
contains digitized versions of an airbrushed map of Mars as
well as a listing of all IAU-approved feature names.
The MDIM CD collection serves two purposes. First, the image
collection serves as a data base for interactive map browser
applications. Secondly, the CD volume set provides a dense
delivery medium to build higher-derived cartographic image
products such as special map series and planning charts for
future Mars exploration missions.
This set contains twenty-two volumes with the following
contents:
Volume 1
--------
Vastitas Borealis Region of Mars (VO_2001): MDIMs in 373
image files covering the entire north polar region of Mars
southward from the pole to a latitude of 42.5 deg. North.
Polar Stereographic projection images of the North pole area
from 80 to 90 degrees are located in the POLAR directory on
this disk
Volume 2
--------
Xanthe Terra Region of Mars (VO_2002): MDIMs in 412 image
files covering the region of Mars from 47.5 deg. North
latitude to 47.5 deg. South latitude, and 0 deg. longitude
to 90 deg. West longitude.
Volume 3
--------
Amazonis Planitia Region of Mars (VO_2003): MDIMs in 412
image files covering the region of Mars from 47.5 deg. North
latitude to 47.5 deg. South latitude, and 90 deg. West
longitude to 180 deg. West longitude.
Volume 4
--------
Elysium Planitia Region of Mars (VO_2004): MDIMs in 412 image
files covering the region of Mars from 47.5 deg. North
latitude to 47.5 deg. South latitude, and 180 deg. West
longitude to 270 deg. West longitude.
Volume 5
--------
Arabia Terra Region of Mars (VO_2005): MDIMs in 412 image
files covering the region of Mars from 47.5 deg. North
latitude to 47.5 deg. South latitude, and 270 deg. West
longitude to 0 deg. West longitude.
Volume 6
--------
Planum Australe Region of Mars (VO_2006): MDIMs in 373 image
files covering the entire South polar region of Mars
northward from the pole to a latitude of 42.5 South latitude.
Polar Stereographic projection images of the south pole area
from 80 to 90 degrees are located in the POLAR directory on
this disk.
Volume 7
--------
Digital Topographic Map of Mars (VO_2007): MDIMs of the
entire planet at 1/64, 1/16, DTMs of the entire planet at
1/64, 1/16, and the digitized airbrush map of Mars at 1/16
and 1/4 deg./pixel.
Each of the first six volumes contains MDIMs of the areas
specified at resolutions of 1/256 deg./pixel (231m) and at
1/64 deg./pixel (943m). Volumes 1 and 6 also contain MDIM
coverage of the entire planet at 1/16deg./pixel (3.69 km).
The six volumes also include a digitized airbrush map of the
entire planet at 1/16 deg./pixel (3.69 km) and at 1/4
deg./pixel. The Sinusoidal Equal-Area Projection, is used as
the map projection for this image collection. For a detailed
description of the Sinusoidal projection and use of the
cartographic keywords found in the image labels, refer to
Appendix E of this document.
The tiling layout of the 1/64 deg./pixel digital models is
the same on the first six volumes. Note that the 1/64
deg./pixel MDIM, segments of which appear in Volumes 1
through 6, is duplicated in its entirety on Volume 7. All of
the resolution compressions were done by averaging, not by
subsampling. A gazetteer of IAU-approved feature names,
referenced by latitude/longitude coordinates is included as a
table file on each of the seven volumes. The digital
Multi-look Color MDIMs are stored on seven CD volumes as
shown in the listing below:
Volume 8
--------
Vastitas Borealis Region of Mars (VO_2008): Color MDIM image
files covering the entire north polar region of Mars
southward from the pole to a latitude of 37.5 deg North.
Polar Stereographic projection images of the north pole area
from 80 to 90 degrees are located in the POLAR directory on
this disk.
Volume 9
--------
Xanthe Terra Region of Mars (VO_2009): Color MDIM image files
covering the region of Mars from 37.5 deg North latitude to
52.5 deg South latitude, and 0 deg longitude to 90 deg West
longitude.
Volume 10
---------
Amazonis Planitia Region of Mars (VO_2010): Color MDIM image
files covering the region of Mars from 37.5 deg North
latitude to 52.5 deg South latitude, and 90 deg West
longitude to 180 deg West longitude.
Volume 11
---------
Elysium Planitia Region of Mars (VO_2011): Color MDIM image
files covering the region of Mars from 37.5 deg North
latitude to 52.5 deg South latitude, and 180 deg West
longitude to 270 deg West longitude.
Volume 12
---------
Arabia Terra Region of Mars (VO_2012): Color MDIM image files
covering the region of Mars from 37.5 deg North latitude to
52.5 deg South latitude, and 270 deg West longitude to 0 deg
West longitude.
Volume 13
---------
Planum Australe Region of Mars (VO_2013): Color MDIM image
files covering the entire South polar region of Mars
northward from the pole to a latitude of 52.5 South latitude.
Polar Stereographic projection images of the south pole area
from 80 to 90 degrees are located in the POLAR directory on
this disk.
Volume 14
---------
Global Mars Coverage (VO_2014): Color MDIM image files stored
in 8-bit color CompuServe GIF format. Images files from
volumes 8-13 stored in a compressed format on this volume.
(see section 5.6)
Each of the volumes 8-14 contains Multi-look Color MDIMs of
the areas specified at resolutions of 1/64 deg/pixel (925m).
Each volume also contains black-white MDIM coverage of the
entire planet at 1/16 deg/pixel (3.70 km). The volumes
include a digitized airbrush map of the entire planet at 1/16
deg/pixel (3.70 km) and at 1/4 deg/pixel. Special color data
products exist in the SPECIAL directory. These image files
contain orthographic, point-perspective, and oblique views of
the planet. A gazetteer of IAU-approved feature names,
referenced by latitude and longitude coordinates is included
as a table file on each of the volumes.
The tiling layout for the Multi-look Color MDIM collection is
the same layout as found on volume 7. The image data are
projected to a Sinusoidal Equal-area Projection. Each tile
contains approximately 1000 lines and samples, and contains
15 degrees of latitude and longitude at the central
latitudes. The high resolution MDIMs are stored on eight CD
volumes as shown in the listing below. The directory and
file naming schemes are described ahead in Chapter 8 'Files,
Directories, and Disk Contents', of this document.
Volume 15
---------
VO_2015 contains quadrangles within the range of 0.0 to 60.0
degrees longitude. These include image data for the Acidalia
Planitia, Argyre Planitia, Ganges Chasma, and Kasei Valles
regions. South pole quadrangles are also included on this
volume.
Volume 16
---------
VO_2016 contains quadrangles within the range of 60.0 to 90.0
degrees longitude. These include image data for the Valles
Marineris, Kasei Valles, Mariotis Tempe, Tempe Fossae
regions. South pole quadrangles are also included on this
volume.
Volume 17
---------
VO_2017 contains quadrangles within the range of 90.0 to
120.0 degrees longitude. These include image data for the
Claritas Fossae, Tharsis Montes, Mariotis Tempe, and Alba
Patera regions.
Volume 18
---------
VO_2018 contains quadrangles within the range of 120.0 to
150.0 degrees. These include image data for the Tharsis
Montes, Olympus Mons, and Acheron Fossae regions.
Volume 19
---------
VO_2019 contains quadrangles within the range of 150.0 to
210.0 degrees longitude. These include image data for the
Arcadia Planitia, Ma'adim Valles, Apollinaris Patera, and
Orcus Patera. North pole quadrangles are also included on
this volume.
Volume 20
---------
VO_2020 contains quadrangles within the range of 210.0 to
300.0 degrees longitude. These include image data for the
Borealis Planitia, Tyrrhena Patera, Isidis Basin, and
Nilosyrtis Mensae regions.
Volume 21
---------
VO_2021 contains quadrangles within the range of 300.0 to
330.0 degrees longitude. These include image data for the
West Hellas Planitia and Arabia North regions.
Volume 22
---------
VO_2022 contains quadrangles within the range of 330.0 to
360.0 degrees longitude. These include image data for the
Arabia West and Acidalia Planitia regions.
Each of the volumes 15-22 contains MDIMs of the areas
specified at 1/1024 degree/pixel (58 meters/pixel)
resolution. This image collection is presented in the
Sinusoidal Equal-Area Projection. For this high resolution
data set, each MDIM 1:500,000 quad for which high resolution
coverage was available has been divided into sixteen tiles
each approximately 1.25 x 1.25 degrees square. Each set of
sixteen tiles exist in a single directory on the CD. See
Chapters 7 and 8 of this document for further discussions
regarding the MDIM tiling schemes and file and directory
naming structure.
Processing Level Id : 5
Software Flag : N
Processing Start Time : 1990
Processing Stop Time : 1991
Parameters
==========
Description
-----------
Data Number is an integer expressing the digital value of an
experiment's telemetry data.
Sampling Parameter Name : PIXEL
Data Set Parameter Name : DATA NUMBER
Data Set Parameter Unit : DIMENSIONLESS
Source Instrument Parameters
============================
Instrument Host ID : VO1
Data Set Parameter Name : DATA NUMBER
Instrument Parameter Name : RADIANCE
Important Instrument Parameters : 1
Instrument Host ID : VO2
Data Set Parameter Name : DATA NUMBER
Instrument Parameter Name : RADIANCE
Important Instrument Parameters : 1
Processing
==========
Processing History
------------------
Source Data Set ID : VO1/VO2-M-VIS-2-EDR-V2.0
Software : PICS
Product Data Set ID : VO1/VO2-M-VIS-5-DIM-V1.0
Software 'PICS'
---------------
The Planetary Image Cartography System (PICS) is an
integrated computerized image processing and cartographic
system for the systematic reduction, display, mapping, and
analysis of planetary image data.
A design goal in PICS was to develop a single set of generic
software, simple to use, that would process any of the
150,000 planetary images from the Voyager, Viking, and
Mariner Missions. This required standards to be developed so
that formats for the image files, calibration files,
geometric pointing and empherides files for all the missions,
cameras, and targets be identical.
Normally the PICS software modules are executed on images in
groups called procedures. Provided in the PICS software set
are the procedures that are used in the USGS Planetary
Cartography effort. They are referred to as Levels 0 through
4. These five procedures are; Level 0 - data preparation,
read raw planetary image from magnetic tape or CD-ROM to
create a PICS image file, place geometry and camera
instrument mode information in the image file labels for
automatic processing; Level 1 - radiometric correction,
bit-error suppression, reseaux processing, coherent noise
suppression, and various cosmetic processes; Level 2 -
geometric transformation including geometric distortion
removal and projecting an image to a standard map projection
and scale; Level 3 - image mosaicking, and Level 4 -
photometric function processing (both characterizing the
function as well as removing model functions.)
The PICS manual describing more than 130 image processing
programs can be obtained by contacting the Branch of
Astrogeology, United States Geological Survey, 2255 North
Gemini Drive, Flagstaff, AZ, 86001.
Software Name : PICS
Software Type : N/A
Software Release Date : 1988-02-01
Node ID : RAD
Cognizant Engineer : ERIC M. ELIASON
Software Access Description : NOT ACCESSIBLE THROUGH PDS
CATALOG - CONTACT NODE.
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
COMPILATION OF DIMs
-------------------
Digital image models are compiled and archived in four stages
or 'levels', beginning with raw images. All of the
corrections made during these stages have some level of
uncertainty, so the processing sequence is designed to
progress from corrections with the highest probability of
accuracy to the lowest, and intermediate stages are preserved
for future analytical use. Image processing software exists
to perform the various stages of image correction and
enhancement [PETTENGILLETAL1980C; SODERBLOM1978].
LEVEL 1: RADIOMETRIC CORRECTION
-------------------------------
Level 1 processing includes removal of electronic shading,
which is inherent in the imaging system, and artifacts such
as minute dust specks on the vidicon tube, microphonic noise
introduced by operation of other instruments on the
spacecraft during imaging sequences, and data drop-outs and
spikes [WU&DOYLE1990]. Reseau marks are also located and
removed during this stage; their precise locations are
recorded for use during later geometric processing. A
digital image label is created, containing the reseau-mark
locations, geodetic control point and image tie-point
locations, and a computed camera orientation matrix that will
project the frame to a best-fit shape and position in a
mosaic.
Level 1 images have better resolution than those produced at
any subsequent processing level. This is because they have
not been resampled for geometric correction and projection;
some loss of information is inevitable in any resampling,
because the density values of multiple pixels and/or
fractional pixels must be averaged to form new pixels in the
output array. Photographic copies of Level 1 images, with
spatial filter enhancement, are therefore the more useful
photographic materials for visual interpretation. Plans for
publication and distribution of Level 1 images on CDROM have
been cancelled, however, because the processing has become so
efficient that it is less expensive to reprocess images on
demand than to archive previous processing. The control
information and projection matrices contained in Level 1
image labels are preserved as text files, and can be easily
recovered if reprocessing is needed.
LEVEL 2: GEOMETRIC CORRECTION
-----------------------------
Level 2 processing includes removal of camera distortions and
transformation from image to map coordinates in DM format
according to parameters derived at the end of the Level 1
processing phase [BATSON1990A]. The resolution of each frame
is preserved to some extent by oversampling in the output
array; that is, by selecting a resolution step that results
in an image with more lines and samples than the original
image. Distortion corrections are based on preflight
calibration of the reseau. Image transformation is based on
camera orientation matrices derived by photogrammetric
triangulation [25] modified as required for a best fit with
adjacent images. On those images where matrices are not
available, they are derived by matching corresponding points
with images that have matrices.
LEVEL 3: PHOTOMETRIC CORRECTION
-------------------------------
At level 3 processing apparent inconsistencies in surface
brightness caused by variation in illumination geometry and
by atmospheric effects are treated. Atmospheric scattering
is a significant consideration on Mars. Different materials
on any planet have different light-reflecting properties.
Other photometric corrections are effective only to the
extent that all geometric parameters can be modeled. In
general, local topography is not included in the model (i.e.,
the surface model used is flat). Illumination geometry at
each pixel, however, certainly depends on local topography;
unless the topographic slope within a pixel is accurately
known and compensated, the photometric correction cannot be
perfect. All of these conditions are so complex that
photometric correction of planetary images is likely to be
only approximate for some time into the foreseeable future,
although research into the effects and prototype examples of
full three-dimensional treatment are now being pursued. An
obvious example of the complexity of the problem would
consist of a pair of images of the same landform illuminated
from opposite directions. Only an extremely complex
algorithm could accurately modify the shading in one of the
images to match that of the other. No algorithm could
restore detail lost in shadow.
The photometric processing used in this MDIM was necessarily
oversimplified, and incorporates spatial filtration that has
the effect of subduing regional albedo markings.
LEVEL 4: CONTROLLED MOSAICKING
------------------------------
Compilation of an accurate digital mosaic (MDIM) of the
entire surface of a planet is the final stage in the
construction of a DIM. The MDIM is a digital image of the
planet, with uniform resolution throughout. The resolution
of level 2 images used in the compilation is compressed or
expanded to match that of the MDIM.
|
.png)
.png)
