Paper W 3

NEW SPACE TECHNOLOGY ADVANCES KNOWLEDGE OF THE REMOTE
POLAR REGIONS

William R. MacDonald, Chief, Branch of International Activities Topographic Division,
U.S. Geological Survey National Center, Reston, Virginia 22092

ABSTRACT

The application of ERTS-1 imagery is rapidly increasing man's
knowledge of polar regions. Products compiled from this imagery
relating to the experiments being conducted under proposal SR-149
at scales of 1:250,000, 1:500,000 and 1: 1,000,000 are already
providing valuable information to earth scientists working in
Antarctica. Significant finds detected by these "bench mark"
products were glaciological changes, advancement in ice fronts,
discovery of new geographic features, and the repositioning of
nunataks, islands, and ice tongues. In cooperation with the
American Geographical Society and funded by the National Science
Foundation, ERTS imagery has been used for the compilation of a
1:5,000,000-scale map of the Arctic.

Products such as single-scene pictorial images and photoimagery
mosaics have been compiled that often exceed the accuracy of
existing cartographic products in Antarctica. A graticule has
been fitted to the imagery based on a least-squares adjustment
of identifiable control points which were established by standard
surveying techniques as well as by satellite geodesy.

Tests conducted under proposal SR-149 in Antarctica have proven
the feasibility of tracking Navy navigation satellites to
establish ground control for positioning ERTS-1 imagery in remote
areas. ERTS imagery coupled with satellite geodesy shows great
promise and may prove to be the most practical and cost effective
way to meet the small-scale cartographic requirements of the
polar science community.

Prepared for presentation at the Third ERTS-1 Principal Investigator's Symposium - December 10-13, 1973, Washington, D. C.

INTRODUCTION

ERTS imagery perhaps has its most immediate application and benefit to the scientific community in the Antarctic region. Although millions of dollars have been expended over more than 25 years toward obtaining aerial photo coverage for small-scale mapping in the Antarctic, only about one third of the continent has been photographed or adequately mapped. In this regard ERTS offers the most practical means of obtaining cloud-free imagery over the millions of square miles yet to be mapped. ERTS appears to be the only way that the cartographic community has of meeting, in a relatively short period, the demands for small-scale imagery products by national and international polar scientists.

ERTS-1 MSS IMAGERY REQUIREMENTS

The nine experimental areas listed in proposal SR-149 aggregate areas from 60° to 82° latitude in both polar regions and add up to millions of square miles. The number of ERTS images of the areas of interest received from NASA on automatic distribution increased so rapidly that a system of indexing became necessary. To date about 500 scenes over Antarctica and about 3,500 scenes over the Arctic region have been received, amounting to 16,000 individual negatives (4 MSS bands) with cloud cover less than 14%.

Storage and retrieval of each ERTS-1 70-mm image and each 1:1,000,000-scale contact print were done manually, but it was too time consuming to search the files for the best imagery, and the cartographer could never be sure that all the available imagery had been reviewed. What was needed was an efficient system that would tell the cartographer the cloud-cover percentage of any particular ERTS image.

IMAGERY INDEXES

To meet these needs indexes were designed in graphic form (fig. 1). They have proved convenient to prepare and practical to use. A CalComp drum plotter was used to plot the individual scenes with identifying scene numbers. The original index plots were prepared on a stable transparent base and keyed to a 1:10,000,000-scale base map. Each 18-day cycle is depicted on two index sheets--odd days on one sheet and even days on another. Data used to plot these indexes were obtained from punched cards from the U.S. Geological Survey's EROS Data Center, Sioux Falls, S. Dak.

Separate indexes show imagery with percentages of cloud cover:
0 to 14, 15 to 34, and 35 to 54. A composite index showing all
available imagery, with cloud cover from 0 to 100 percent, was
prepared for each 18-day cycle.

Figure 1.--ERTS-1 Imagery Index Binders. The Arctic and Antarctic binders are prepared at 1: 10,000,000 scale for each 18-day cycle and depict percentages of cloud cover.

Transparent or paper copies can be produced by the diazo process.
Copies of the indexes of the polar regions can be purchased from the
USGS, Map Information Office, National Center, 12201 Sunrise Valley
Drive, Reston, Va. 22092. Transparent copies cost $3.50 each,
and paper copies cost 75 cents each.

As a spinoff benefit, copies of all ERTS Imagery Indexes are being made available to member nations of the Scientific Committee on Antarctica Research. Japan, Argentina, Australia, and South Africa are currently investigating the use of ERTS imagery over their areas of interest in Antarctica as a direct result of investigations carried out under this proposal.

IMAGERY PRODUCTS

Although we have a long way to go, ERTS has already disclosed a few of Antarctica's secrets. Products compiled in accordance with the objectives outlined under proposal SR-149 have demonstrated their value to the polar research community. Orthoimage products compiled include 1:1,000,000-scale imagery mosaics and single-scene 1:250,000and 1:500,000-scale gridded images. Imagery has also been used as a source for recompilation of small-scale maps in the Antarctic and Arctic regions. Significant finds resulting from analysis of these products include discovery of new geographic features, advances in the world's largest ice fronts, coastal glaciological changes, and repositioning of nunataks, islands, and ice tongues. Figures 2, 3, and 4 are examples of imagery application.

Our preliminary results, which have been published1, indicate that ERTS imagery has the potential for rapid compilation of orthoimage products that meet the small-scale map requirements of the cartographic and scientific communities. However, the usefulness of any ERTS imagery product is extremely limited unless the image data can be related to an Earth reference system. Therefore, ground control points must be used to maintain the relative and absolute relationship between image points and their earth positions. Thus, if ERTS imagery is to be fully utilized as a cartographic and scientific tool, a framework of geodetic control must be available to relate the image data to an Earth reference system.

MEETING ERTS POLAR REGIONS CONTROL REQUIREMENTS

Since control in the polar regions is very sparse and extremely expensive and difficult to establish, it was necessary to find an economical means of acquiring the amount of control needed to maintain the integrity of ERTS cartographic products.

1R. B. Southard and W. R. Mac Donald, The Cartographic and Scientific Application of ERTS-1 Imagery in Polar Regions (A.6.4.), presented at the Symposium on Approaches to Earth Survey Problems, Konstanz, FRG, May 1973.