Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [WP-5 LARGE SHARED DATABASES]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: PIXELS AND CENSELS: PUTTING PEOPLE IN THE PICTURE. Robert W. Marx

Document type:: Multivolume work

Structure type:: Chapter

494 driven plotters, and new host minicomputers that the staff needed to conduct the numerous activities asso ciated with building and using the TIGER data base. • To build a computer file containing every known street and road in the United States (see Notes 1 and 3), the name (or names) of each, and the range of address numbers located along each segment of every street in the 345 largest urban areas of the United States; all the railroads in the United States; all significant hydro- graphic features and their associated names; named landmark areas such as major parks and military bases; and essential “key geographic locations” such as named apartment buildings, shopping centers, fac tories, and office buildings that are important as alternate ways to address mail. • To enter and verify the boundaries, names, and numeric codes for all the geographic entities used by the Census Bureau to collect and tabulate the results of both the 1980 and 1990 decennial censuses of the United States. In doing this, the TIGER data base also includes most of the more limited set of geographic entities used for the economic and agriculture censuses of the United States (U.S. Bureau of the Census, 1985a). (See Figure 1) The Process The Census Bureau derived the initial set of information this data base contains from three primary sources: 1. The 1980 census GBF/DIME-Files — covering less than 2 percent of the land area but 60 percent of the people in the United States -- were the primary source for the Nation’s major urban areas. The GBF/DIME- Files contained the features, feature names, and ad dress ranges compiled by the local officials who helped the Census Bureau create those files over the course of 12 years and two decennial censuses — information presumed to be basically correct except for changes since the last update of the GBF/DIME-Files in 1976. 2. A cooperative program with the U. S. Geological Survey (USGS) -- “the national mapping agency” for the United States -- provided the primary source for most of the remaining 98-plus percent of the Nation’s territory (McKenzie and LaMacchia, 1987). The features in the USGS files were compiled to National Map Accuracy Standards using aerial photography that was no more than 3 years old at the time a particular map was prepared — and most were prepared during the 1983-1987 project period. This was in contrast to the 1980 census when the maps used for the 98-plus percent of the Nation outside GBF/DIME-File areas were “the best the Census Bureau could find” — often state and local maps with compilation dates 10, 20, or more years earlier. 3. For Alaska, Hawaii, Puerto Rico, and the other areas for which the Census Bureau created the TIGER data base (see Note 1), the Census Bureau digitized available maps — typically published USGS quadrangles ranging in scale from 1:20,000 for Puerto Rico to 1:250,000 for the remote areas of Alaska. These maps varied widely in age. To make the information in the initial TIGER data base more current for 1990 census operations, the geographic staff in the Census Bureau’s 12 regional offices collected the latest available maps from local officials across the United States. The geographic staff then compared the information shown on those local maps with the information contained in the developing TIGER data base. Where there were differences, they inserted new streets and roads, and appended street and road names to those new features when the local maps showed names for them. The geographic staff also used those locally collected source maps to append names to all the streets and roads that entered the TIGER data base from the USGS files; those files came to the Census Bureau with no names. This work was done over a period of 4 years, using quality control checks designed to keep the number of clerically induced errors at “normal” levels (Marx and Saalfeld, 1987). This development task is complete; the goal of supporting the 1990 census, nearly met. The resulting computer file contains a latitude and longitude coordinate value for each of the more than 28 million feature intersection and end points that define the nearly 40 million feature segments that outline the approx imately 12 million polygons in this giant "connect-the- dots" map of the United States. The foregoing leads, more logically at this point, to a discussion about geographic information systems (GIS). GIS APPLICATIONS What is a GIS? The debate goes on endlessly. Some argue that the only “true” GIS is a computer system that processes “overlays” of information. Others contend that a GIS must include natural resources data. Still others debate the level of accuracy one needs in the coordinates that define the features and data polygon boundaries comprising the GIS. Without endorsing or excluding any of these definitions, providing a more generic defini tion may help the average citizen understand the value of a GIS. The more generic definition is: A computer system that helps people discover relationships between and among sets of geographi cally-referenced data that they could not see or understand easily without the aid of this technology. Whichever definition one accepts, the facts show that GIS technology is helping the United States and many other countries around the world study the numerous environments and changes that surround us. These enormous amounts of money and energy are being spent under the rubric of “global change.” In the more generic context suggested above, it seems that the users of most GIS products available thus far have focused on physical features and natural resources data. In doing so, they typically have ignored one other important factor that surrounds us — people! People in a GIS People inhabit almost every part of the earth. They either affect what is going on or are affected by what is going on. This is especially relevant if one accepts the predictions of many demographic experts who project that in the next 50 years, the earth’s population will double (Torrey, et al., 1989). They also project that this growth will continue the dramatic shift from rural settlement to urban settlement with the urban pop ulation likely to triple in the same 50 years. Certainly these shifts are having — and will continue to have — a significant effect on the world in which we live. For this reason, it is desirable that people be a “layer” in a GIS. Perhaps the omission of “people” information from most GIS studies has resulted because this “people” infor mation traditionally has not been in a form that com puters could process conveniently in a GIS context. With natural resources data from satellite imagery, the opposite has been true. It streams down from the sky with, as Carl Sagan would say, its "billions and billions” of pixels. The pixels in a satellite image basically portray little polygons or rectangular sections of the earth’s surface. The resolution of those pixels varies from “coarse” to “fine,” depending on the sensitivity of the instruments in the satellite transmitting them.

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