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avhrrima.txt
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1997-09-23
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We have included for your enjoyment a Satellite Image Map of Antarctica
Using Advanced Very High Resolution Radiometer (AVHRR) Images that
was downloaded from a USGS web page.
This is the information contained on that web page for the image Antarctica.jpg
and Antarctica.pcx. These are Black and White data. The folder COLOR contains
a mosaic of a color image of Antarctica. The images are in .gif format.
The image ANTColor.jpg is a composite image of the mosaic of color images.
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[Black and White AVHRR Mosaic] A major advantage of remotely sensed
satellite images collected from space is the regional/synoptic view of the data.
The regional perspective view is
enhanced further by digitally mosaicking different images collected by the
same satellite to cover an even larger regional area. Another advantage is
the multitemporal aspect of satellite images, which can be used to monitor
changes on the Earth's surface or update an existing data set. In this
particular case an existing digital satellite image mosaic was updated with
newer and better images to replace cloud covered areas and digital image
processing techniques were used to improve the presentation of the data.
The United States Geological Survey's (USGS) Mini Image Processing System
(MIPS) was used to apply the geometric, radiometric, and spatial filtering
required to update and improve the existing digital mosaic, as well as the
merging of the AVHRR and topographic images. The digital image map results
shown here were published in hardcopy format as USGS Miscellaneous
Investigation Series Map I-2560. It is an image map at a scale of
1:5,000,000 with selected geographic names and contours printed on the
image base. The image map was prepared by the USGS with joint support from
the National Science Foundation Interagency Agreement OPP-9114787. The
following text, with slight modifications, was extracted from the published
hardcopy version.
The satellite images used in the mosaic were acquired by the Advanced Very
High Resolution Radiometer (AVHRR) sensors on the National Oceanic and
Atmospheric Administration (NOAA) satellites; the images used in the mosaic
were collected during the period 1980 to 1994. Although the AVHRR scans a
2400 km-wide swath and can image nearly half of the continent of Antarctica
on a single orbit, 63 sections of 38 scenes were needed to compile the
nearly cloud-free digital mosaic.
The digital image mosaic used as input was previously mosaicked,
controlled, and geometrically corrected into a Polar Stereographic
projection by the National Remote Sensing Center, United Kingdom. Details
of the processing they used to generate the original mosaic can be found in
the International Journal of Remote Sensing (1989, v. 10, nos. 4 and 5, p.
669-674). The USGS evaluated the geometric accuracy of the mosaic and
estimated a root-mean-square error of 2.5 km. The digital image processing
that created this modified image base was done at the USGS Flagstaff Field
Center, Flagstaff, Arizona. Replacement images were geometrically corrected
to the first image base, digitally inserted into the mosaic, and
radiometrically/tone matched to blend with the surrounding images. When the
entire mosaic was completed band 1 (visible, 0.58-0.68 micrometers) and
band 2 (near-infrared, 0.725-1.100 micrometers) were averaged, and the
entire digital mosaic was enhanced using a 91 by 91 pixel spatial filter;
the results were contrast stretched.
The published hardcopy version, USGS map I-2560 authored by:
Jane G. Ferrigno, Jerry L. Mullins, JoAnne Stapleton,
Pat S. Chavez, Jr., Miguel G. Velasco, Richard S. Williams, Jr.,
George F. Delinski, Jr., and D'Ann Lear
is for sale by the U.S. Geological Survey Information Services, Box 25286,
Federal Center, Denver, CO 80225.
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[Color Composite of the AVHRR Mosaic] The black and white image shown
above is equivalent to the image map published in hardcopy format. To show the
multispectral (color) information contained in the data, a color composite was made
using the processed and enhanced spectral bands 1, 2, and their sum; they were used
as blue, green, and red, respectively. In the visible and near-infrared
spectral regions snow and ice are relatively flat, however, enough color
differences exist that variations among snow, ice, blue ice, and exposed
rock can be seen.
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Antarctica DEM, Shaded Relief, and Stereoscopic AVHRR Images
The Antarctica Digital Elevation Model (DEM) was acquired from a USGS EROS
Data Center world wide web page, and are part of the global GTOPO30 data
available from the EDC. The DEM data, like the AVHRR mosaic, are in a polar
stereographic projection with 1 km resolution and only simple scaling and
translation were used to geometrically register the two images. The
documentation supplied with the DEMs state that they were generated from
contour and coastline data made available by the Antarctic Digital Database
(ADD), which was produced under the guidance of the Scientific Committee on
Antarctic Research (SCAR). These data were then used as input to the
Australian National University Digital Elevation Model (ANUDEM) computer
program developed by Michael Hutchinson. The absolute accuracy of the DEM
grid has not been measured or calculated. The original data and maps used
to compile the final DEM had better spatial resolution and height accuracy
along coastal areas; this data quality difference is visible in both the
compressed DEM and shaded relief images shown on the following page:
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Project Team:
Pat S. Chavez, Jr. Remote Sensing Scientist/ Team Leader
Jane G. Ferrigno Geologist (Remote Sensing)
Miguel G. Velasco Lead Image Processor on this project
Jo-Ann Bowell Image Processor
Stuart C. Sides Computer Scientist
Cheryl Hallam Geographer (GIS)
Rosendo R. Gonzalez Programmer
Deborah L. Soltesz Web Page Design
For more information about this project, contact:
Pat S. Chavez, Jr. Jane G. Ferrigno
Email: pchavez@ogre.wr.usgs.gov Email: jferrign@usgs.gov
U.S. Geological Survey U.S. Geological Survey
2255 N. Gemini Dr. 955 National Center
Flagstaff, AZ 86001 Reston, VA 20192
Tel: (520) 556-7221 Tel: 703-648-6360
FAX: (520) 556-7169 FAX: 703-648-6524
Send questions, comments, suggestions to webmistress@TerraWeb.wr.usgs.gov
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URL of the title page for this project:
http://TerraWeb.wr.usgs.gov/TRS/projects/Antarctica/AVHRR.html
Last Modified: 24 February 1997