Why do mappers need control and intelligence anyway ?
Dr. Donald R. Woodley, Dr. Tarek M. Elgarf
Intergraph Corporation (IW-17A6)
One Madison Industrial Park
Huntsville, Alabama 35807 USA
Abstract
In order to deal appropriately with the critical features of the continued growth in the population and infrastructure of developing countries, there is an apparent need to strengthen the capability of natural resource agencies to collect and manage spatial information. However, it is not just the existence of land-related information which will help decision making by government, business, industry and individual residents. Rather it is the timely access to reliable data that is important.
Generally it has been accepted that a geographic information system is a digital computer system which allows users to collect, manage and analyze large volumes of spatially referenced and associated attribute data. Seldom addressed during the early design stages of these systems for natural resource applications are the issues of appropriate attribution and the effects of positional control on the relative accuracy of the resultant information. It is recognized that the costs to capture the spatial data sets from remotely sensed information and existing maps and the associated intelligence for use in a resource management system can be expected to far exceed the cost of hardware and software: and often the standards of accuracy and minimum reliability of the information must be related to the local situation. However, in creating the data sets for resource management positional control, data encoding schemes, topological data structuring, attributing of information and selection of file structures must all be performed in a manner to support the users applications. This is a set of complex and time-consuming tasks, particularly for the inexperienced user. Failure to capture the correct data in positional correct form, with adequate associated attribution is likely to result in the management system being unable to support its intended users.
This paper will introduce the reader to various issues related to the potential and limitations of creating and maintaining modern digital maps and attribute information. These issues include aspects of map data collection, control accuracy, intelligence and utilization.
Why do mappers need control and intelligence anyway?
Introduction
Effective resource management is based upon the premise that the same land information regularly is needed by many different agencies, organizations, and individuals for a disparity of purpose. Historically the traditional maps and surveys were valuable tools for representing these data in space. However, the hard copy maps have the disadvantages of relatively low accuracy in terms of positional error, they are dated to the time of compilation, and the intelligence conveyed to the use is limited to the contents of the printed map. Initial creation and subsequent updating of printed maps by traditional cartographic techniques is a time-consuming, tedious process requiring manual drafting, scaling and transfer of information from one map source to another. Typically these processes periodically require significant investments of time and capital to minimize obsolescence of the cartographic products.
In contract with the methods employed to produce the traditional cartographic products, most state-of-the-art digital resource management systems (RMS) possess full functionality for entering, storing, updating, retrieving, and analyzing spatial information: many of these operations can be accomplished automatically. The resultant data sets are unique in providing the geographic positions of features which are related to known coordinate systems, and which describe the spatial and topological relationships among features in the digital information. The essence of RMS is the ability to link a multitude of resource related attributes, often from many different sources and maintained by different organizations, to a unique geographical location or area.
However, these digital systems also have shortcomings which must be considered by potential users. The manual cartographer nearly always works with the entire map sheet, whereas in the computer environment, operators typically work with only a portion of a data base. The production map generally presents marginal information regarding accuracy, scale, and data sources: in the computer environment, the user may not have access to information on the data sources, accuracy, or even the compilation scale of the origin map data. As a result of these constraints the digital cartographer may loose perspective on fundamental issues regarding the sources and compilation of the map information.
It is likely that future RMS will reside in digital computer systems which have been programmed to manage resource data and to allow many different methods of analysis. Common throughout much of the contemporary cartographic literature are the basic requirements for this kinds of systems: to have cartographic, geodetic and cadastral data bases as the common thread which links ownership parcel data and administrative/political information to all resource-related information.
