Mapping geomorphology: A journey from paper maps, through computer mapping to GIS and Virtual Reality

ET-SEVIER

Geomorphology 16 (1996) 233-249

Mapping geomorphology: A journey from paper maps, through computer mapping to GIS and Virtual Reality John D. Vitek a, John R. Giardino b, Jeffrey W. Fitzgerald ’ a School of Geology, Oklahoma State University, Stillwater, OK 74078, USA b Departments of Geography and Geology, Texas A&M University, College Station, TX 77843, USA ’ Department of Geography, University of North Texas, Denton, TX 76203, USA Received 27 April 1994; accepted 4 March 1995

Abstract Maps are integral components of research in geomorphology and Quaternary geology. Visual presentation of the spatial and temporal distribution of a phenomenon often provides clues to the process(es) that generated the phenomenon. Compiling information on maps, interpreting spatial patterns, and using standard topographic maps were fundamental parts of the undergraduate experience. Why have such experiences been slowly disappearing from undergraduate curricula? How are geology majors taught map scale, map projections, and the pitfalls associated with the display of spatial information? Neglect in preserving the mapping tradition places the geology major at a disadvantage. The use of maps and mapping is undergoing a renaissance; use in the classroom has a bright future because of digital scanning, computer cartography, geographic information systems (GIS), and virtual reality. Pen and ink techniques should be relegated to museums. Pencil sketches can be scanned and perfect products generated every time. These techniques, however, do not eliminate the need for basic map knowledge such as scale, projections, and generalization. What assumptions about map projections have been built into the software? How are spatial data and attribute data integrated into the resultant map in a geographic information system (GIS)? Because the application of virtual reality to geomorphic processes looms on the horizon, geologists must recognize how the current spatial revolution can help with the assessment of geologic phenomena and teach students to function with the new technology.

1. Introduction

The value of a map in the study of the spatial distribution of phenomena was recognized long ago in the saying “a map is worth a thousand words”. As the data displayed on a map have increased in complexity, the saying remains true because of the difficulty of describing any spatial pattern with words or numbers. But as the techniques to produce a map have changed from pen and ink to computer graphits, it has become easier to create attractive maps

that attempt to transmit spatial data from map makers to map users. The complexity of a map is no longer constrained by the ability to create a final product. No longer must students, as map makers, be subjected to the “joy” associated with mastering a ruling pen, a “Rapidograph”, “zip-a-tone”, or LeRoy lettering. In contrast with hand production, any map can be produced and modified rapidly using computer graphics with minimal frustration. Modem techniques are changing the production, use, and storage

0169-555X/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDZ 0169-555X(95)00131-X

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of maps. Because the amount of data and the rate of data acquisition are increasing exponentially, both producers and users of geologic data must be intimately knowledgeable about the basic precepts of cartography and be familiar with modern technology. Thus, our objective is to review fundamental concepts of cartography and to discuss the technological progression of cartography from traditional pen and ink to computer applications. Because we think the future of geologic mapping is linked to geographic information systems and scientific visualization, we devote the second half of this paper to providing an overview of these technologies. The constraints on map use today result from the inability of a map user to interpret the map. This paper alerts map makers and map users that awareness and knowledge of basic spatial concepts must be taught to students to insure that maps are both correctly produced and interpreted during the analysis of geologic phenomena such as landforms and geomorphic processes. How do we know that a problem exists? One does not have to look far to find examples of the misuse of maps. The depiction of boundaries associated with the plate tectonic theory on a Mercator projection indicates that some map makers are not aware of the limitations of map projections. Because the map user may lack knowledge of projections, a false impression of the spatial relationships of any data displayed on such a projection may be acquired. With advances in automation in map-making, awareness of basic mapping concepts, including symbolization, projections, scale, and generalization, must be re-introduced into the curriculum rather than left to chance. Specialization in maps and mapping require as much attention in the curriculum as new advances in geochemistry, geophysics, dating techniques, or computer programming. Students must be prepared for these advances before they enter the job market.

2. Definition of map Maps are commonly used in most geology classes to display the spatial distribution of phenomena. Textbooks contain many examples of spatial data on maps for instructional purposes. Too often, however, the concepts of map creation and map use are not

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presented in class or in the text. An assumption has been made for years that all geology students are knowledgeable about maps. Laboratory exercises in Introductory Physical Geology focus primarily on how to read a map. To overcome the lack of map knowledge, we have elected to begin this presentation on mapping at the beginning by defining a map as the symbolization of reality (Robinson et al., 1984). The map maker uses symbols, specifically points, lines, and areas, to create an impression of reality for the map user (Fig. 1). The objective of a map is to transmit temporal-spatial information from the real world to a user and to have the user gain a perspective of reality. The goal is to provide the user with as much knowledge of the real world as the limitations of the process of making the map will permit. In the example (Fig. I), the map user should be able to comprehend where the study area is located in southern Colorado and where the specific site is located. This knowledge was gained by observing the unique combination of points, lines, and areas that contributed to the specific purpose of the map (Nelson, 1980). Whereas complete knowledge of the study site (i.e., reality) can never be accomplished with this map or any map, the user will have at least some knowledge of where the research was performed. Every map, no matter how complex or simple, is the spatial arrangement of symbols representing reality.

3. Map projection To display Earth or portions of it on a map requires transforming a three dimensional object (i.e., Earth) into two dimensions (i.e., the sheet of paper or a computer screen>. Because a sphere cannot be transformed into a two dimensional object without distortion (i.e., stretching, tearing, and compression), maps contain a variety of errors even when special care is taken during the process of transformation to retain some special relationships on the map. For example, map projections exist that preserve shape, size, or distance. However, preserving one of these characteristics results in greater distortion in one or both of the other characteristics (Robinson et al., 1984). As a result, each map projection has been

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designed for a specific purpose which then makes it unsuitable for other purposes. A review of the maps in many geology textbooks, in professional journals, and some used at presentations confirm that maps are often used incorrectly. As a result, any conclusions about the distribution of spatial data from the pattern on an incorrect projection may be flawed. Students in an introductory cartography class learn that map projections are designed as cylindrical, conic, or planar because these objects can be easily displayed in two dimensions (Robinson et al., 1984). They also learn that each projection has special properties to accurately display information on the map. Numerous sources, such as Dyer and Snyder (1989) and Wikle (19911, are available to assist map makers with the selection of the best map projection

for the purpose of the map. The most comprehensive review of map projections and associated characteristics, however, is a recent U.S. Geological Survey publication by Synder (1987). Clearly, the most frequently misused map projection is a cylindrical projection called the Mercator projection in honor of its creator Gerardus Mercator. Because of simplicity of construction, it is frequently used to display every global pattern imaginable. A quick perusal of 15 introductory geology textbooks shows 100 percent employ the Mercator projection to show global patterns of various phenomena (Fig. 2). But the only purpose for a Mercator map projection is to permit rapid determination of the direction to navigate from point to point. Because of the great area1 distortion on this projection, it has absolutely

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enhance lands.”

Fig. 2. The Ring of Fire when displayed on a Mercator Projection gives a distorted view of the tectonic activity in the polar regions (adapted from Press and Siever, 1986 and Ernst, 1990).

no value for displaying any spatial information. In most instances, only the equator on the map is identical with the equator on Earth. At 60”N or 60”s latitude, for example, the map has been stretched to twice normal size in comparison to the length of these latitudes on the globe. The rate of stretching increases at an even greater rate toward the poles, which never can appear on the projection if the equator is the line about which the projection is constructed. The use of this map in introductory geology texts continues to propagate a distorted view of the size of continents. Strahler and Strahler, 1983, p. 15) clearly make the point about the pitfalls of the Mercator projection:

“Although indispensable for navigational uses, the Mercator projection has serious shortcomings for use as a world map to show geographic information dealing with areas of distribution. Except for the equatorial region (for which it provides an excellent grid), distortions of scale are very serious. Because of infinite stretching toward the poles, this map fails completely to show how land areas of North America, Asia, and Europe are grouped around the polar sea. In the mind of an inexperienced user, it may

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Misuse of the Mercator projection has caused inexperienced students to develop an incorrect perception of geographic distribution of geologic phenomena. For example, an introductory class student examining a map showing plate boundaries in any geology textbook will receive the incorrect impression that the Pacific Plate appears to be as extensive at its northern extent as along the equator. This perception is incorrect. A comparison of the area1 extent of the Pacific Plate shown on a Mercator projection with the same area on a globe clearly reveals the distortion. Map projections cannot be used effectively without knowledge of the basic qualities imparted to the map during the transformation process. Using a map projection because it happens to be convenient demonstrates an ignorance about the importance of the spatial relationships created by the projection. With greater reliance upon spatial data as input to geographic information systems (discussed in detail later in the paper), the special properties of each map projection acquire greater importance. In which class or classes taken by geology majors are these basic cartographic concepts introduced? If students are not being trained relative to map projections and mapping concepts, the basic question that a program must answer is why not? How are students supposed to acquire knowledge pertaining to the spatial display and assessment of data on a map? Recently, the U.S. Geological Survey published a poster with an image of Gerardus Mercator on one side and a summary of the types of map projections and associated special characteristics on the reverse side (U.S. Geological Survey, 1990). Displaying this poster in labs would alert students and faculty to the importance of map projections. Other sources of information about map projections include Synder (1987), Muehrcke (1986), and Greenhood (1964). As more and more mapping activities are accomplished on computers, special attention must be given to map projections and the properties of each projection that helps the map user gain accurate information about reality. One may ask why is it so important to use the correct projection? Who really cares? The answer is simple! As more and more decisions are being

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made based upon composite maps generated with a computer, it is imperative that the data be correct. An old adage remains applicable “garbage in, garbage out.”

4. Scale Scale is one of the most confusing aspects of maps. This confusion is caused by a misunderstanding of the arithmetic property of fractions as well as the misunderstanding of spatial resolution. At the center of the confusion is the comparison of large scale versus small scale maps. We believe that the confusion arises because map users forget elementary arithmetic concepts when they look at map scale. Instead of looking at the scale as a fraction or ratio, they look at the denominator only. One must always look at map scale as a ratio. The concept of map scale is simply the relationship of a known distance between two points on a map to the distance between the same two points on Earth. “Large” scale means that the map covers a relatively small area, but contains more detail than would be shown on a “small” scale map. Generally, a “small” scale map shows a large area with few details whereas a “large” scale map shows a small area in great detail. The level of detail created by the visual impression of points, lines, and areas is usually a function of the purpose of the map, the area mapped, and the final production size. On a map with a scale of 1: l,OOO,OOO(one centimeter on the map is equivalent to l,OOO,OOO centimeters or 10 kilometers on Earth) every feature on Earth cannot be displayed on the map. The cartographer (map maker) performs the process of generalization by consciously selecting what information in 10 km will appear on the map in 1 cm. Scale, therefore, restricts what can be displayed and controls the amount of information transmitted about reality to the map user. In general, the larger the map scale, the greater the amount of information the map can display. Reality can be displayed on a map but map scale influences how the map can be used. For example, in producing a geologic map of surficial rock type, a solid line symbol (--_) is used if the contact between different units is visible whereas a dashed line (- - -) is used if the contact is hidden from view.

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If either line has a width of 0.15 mm on the map and the scale of the map is 1:24,000, the line width actually represents a strip 3.6 meters wide on Earth in which the sharp contact one observes on the map between the different types of rock occurs. The map helps a user get into the general locality of a specific point. Whereas great care must be taken in field mapping, once data are displayed at any particular map scale, the details mapped in reality have been generalized.

5. Generalization We were once asked by a student: “With aerial photographs so easy to take and obtain, why do we need maps?” Clearly a major difference between the aerial photograph and the map is that the photograph shows all; a map is selective and can focus attention on specific areas or themes. In addition, aerial photographs have distortion along the margins, whereas maps are planimetrically correct. The cartographer who produces the map employs generalization to achieve a specific purpose. After selection of map projection and establishment of the scale of a map, a map maker employs the concept of generalization. Because everything in reality cannot be shown on a map with a special purpose at a specific scale, information is selectively left off the map. For example, a map may display the distribution of alluvium but ignore lacustrine deposits. The map user would have no knowledge that the map maker elected not to map lacustrine deposits Reduce

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Fig. 3. The process of generalization can eliminate detail but detail cannot be recreated simply by enlarging the scale if C’ is the only information available (from Vitek et al., 1984).

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unless he/she was familiar with reality in the area covered by the map. On Fig. 1, other rock glaciers and talus deposits could have been displayed but were left off the map because the only purpose for the map was to show the location of the rock glacier that was studied. The amount of generalization is usually only known to the map maker. Once the level of generalization has been established for a particular map, it cannot be improved by simply enlarging the scale. Too often an incorrect assumption is made that changing map scale enhances the quality of the map. As shown on Fig. 3, information from reality can be generalized to smaller and smaller scales. If the small-scale map is the only one available, it cannot be used to develop the level of detail possible at a larger scale (Vitek et al., 1984). Students must be informed that the rapid scale changes that can be made on copy machines are useful for creating small scale maps but enlarging the map does not add detail to match the new scale. The important take-home message here is that scale imparts a certain confidence level to the fidelity of data. One assumes geology mapped at a scale of 1:24,000 will be much more accurate and detailed than geology mapped at 1: 100,000. When an individual enlarges a 1: 100,000 map to a 1:24,000 map, a certain level of confidence (false in this instance) is given to the map. Details related to the creation of map projections and the design and making of a map influence how the map can be used. As techniques change and improve the rapidity of map production, the map user must become knowledgeable about the assumptions related to map construction and data display to insure correct utilization of the map. Map projections, scale, and generalization are basic concepts that must be learned whether the final maps have been hand-drawn or generated by a computer.

provide the map user with an excellent image of reality, including elevation. An impression of the third dimension, elevation or the height above mean sea level, is provided to the user through the pattern of contour lines. Because each line connects points of the same elevation, the spatial arrangement of lines permits the map user to form an image of the surface and to draw inferences about the landforms and processes that have shaped it. Many excellent books and articles describe how to interpret topographic maps, including Dake and Brown (192.51, Dury (19521, and Bart (1991). Interestingly, a topographic map has no special properties that result from the projection that creates the map but the large scale permits the map to be used as if it has true direction, equal area, correct distance, and correct angles. Techniques related to the use of topographic maps must be taught to students rather than left to chance. As specialized courses were introduced into the geology curricula, basic courses in maps and mapping were relegated to elective status or dropped all together. Benefits can only be derived from topographic maps if the students understand the assumptions involved in map construction and learn how to “see” the real world through map use. In our opinion, the brief exposure to classic landforms as displayed on maps in an introductory course and a few map reading questions do not provide students with sufficient training in the use of topographic maps. Many human activities require maps with scales larger than topographic maps. Geologists must be adequately trained in map construction and use to be able to make knowledgeable decisions that translate into the safe utilization of the surface.

6. The topographic map

The history of map production dates from crude implements sketching images in the soil to direct others to a location. As the need to know more about other locations increased, people perfected techniques to produce images. Slowly the production of maps changed from labor intensive to the present in which technology minimizes the need for any manual artistry to produce a quality product.

In terms of map use, the topographic map probably is the most important tool in geomorphology and Quatemary geology. These maps, produced at a large-scale of 1:24,000, are also known as 7 l/2 minute series maps because each map generally displays 7 l/2 minutes of longitude and latitude. They

7. Map production

J.D. Vitek et al. / Geomorphology

7.1. Pen and ink techniques For generations students were instructed in a variety of classes on the use of pen and ink to produce a “quality” image. The ease of production evolved as the pens changed from ruling pens, to PelicanGraphos pens, and to reservoir pens, such as the until today when all lines and let‘‘Rapidograph”, tering can be totally produced by a printer driven by computer software. Rationale that pen and ink techniques should not be abandoned include price and the thinking and planning by the student prior to creation of a final product. Pen, ink, and paper are relatively inexpensive compared to the costs associated with hardware and software for computer graphics. Unfortunately, computer graphics are so fast that ‘‘trial and error’ ’ procedures are utilized too often to get something to look good rather than the careful planning in design and data analysis that were required before inking. But students should not be subjected to the frustration of learning pen and ink techniques given the quality that can be obtained with printers compared to images produced by hand. When faculty state that students must have proficiency to produce field sketches in pen and ink, one can counter that scanners can take any pencil sketch and produce perfect final results. Students, therefore, can devote more time to knowledge acquisition rather than preparation of visual displays. Finally, for most classroom activity, pencil sketches should be acceptable. Just because we, the older generation, had to learn pen and ink techniques does not justify its importance. Most of us now rely on computers to generate graphics for publications and presentations, and, therefore, we must be certain that students use modern techniques to fulfill degree requirements. 7.2. Computer graphics Computer mapping began at the end of the 1950s as known values associated with given points or areas were printed on a teletype or a line printer (Nordbeck and Rystedt, 1972). As one can imagine, the output was crude compared to hand-drafted maps. Many different computer programs were written during the 1960s in an effort to generate maps before SYMAP (synographic mapping system) was created

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by Northwestern University and Harvard University (Fisher, 1970). The software could manipulate spatial data but output via a line printer produced a poor visual product. Various shades of gray were created in areas by overstriking different combinations of symbols. Computers could produce maps quickly but the quality associated with manual drafting techniques was missing. Rapid production, however, permitted visual evaluation of numerous data manipulations displayed in map form. The SYMAP technique had limitations such as the number of points used to define the area being mapped and the number of data points within the mapped area. But most limitations were often linked to the size and speed of the computer manipulating the spatial data. From these early efforts, technological advances in hardware and software have completely replaced any need, and we mean any need, for hand-produced maps. Hardware exists that can generate the finest lines and patterns at affordable prices. With scanners, any visual image can be converted into numeric values that can be manipulated by software into a final product of exceptional quality. Recognize a mistake or wish to make a change in the final product-no problem; enter the correction into the computer and print another first-class product in minimal time. Through the 1970s ’80s and into the ’90s as the next generation of hardware and software became available, high prices and associated costs rapidly dropped in response to competition from new, and better, products. Whereas cartography once focused on the creation of accurate and attractive products to transmit spatial ideas, almost anyone can now produce visually pleasing products. Although the important cartographic elements necessary for a good map are included in software routines, the need for cartographic knowledge is essential with respect to the type of map projection on which the data are displayed, the nature of data manipulation, and the best way to portray the data. Default options in the software may not provide the best product for the intended purpose. Too often the older generation refers to some aspect of the past as being “the good old days”. In cartography, be thankful the “good old days” are gone forever because the computer hardware and software revolution has eliminated the frustration of

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making errors in ink that detracted from the quality of the final product. The hardware and software revolution in computer cartography shows no signs of slowing down. Prices continue to decrease on hardware and software while the consumer becomes more sophisticated and better products continue to emerge. What is the best hardware and software depends upon individual needs. Discuss such topics with people producing a range of mapping products before you purchase equipment. As mapping applications, such as the geographic information system, continue to be developed, involvement of computer mapping in decision-making processes will increase in importance. Be certain that your students are prepared to comprehend the vast, exciting realm that awaits their involvement with spatial data.

8. Geographic information systems 8.1. What is a GIS? A logical extension of computerized mapping has been the development of the geographic information system (GIS) (Marble, 1984; Burrough, 1986; Star and Estes, 1990; Laurini and Thompson, 1992). A GIS is a collection of computer-based tools for working with data about phenomena on, above, or below the surface of Earth (Laurini and Thompson, 1992). More specific definitions emphasize various aspects of the computing tools. Burrough (1986) described a GIS as a computing environment consisting of five components: (a) data input; (b) data storage and management; (c) data visualization and output; (d) data manipulation and analysis; and (e) user interface. Recently, D. Sui (pers. commun., November

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1993) expanded on Burrough’s (1986) tool-based definition by explicitly including trained personnel and geographically referenced data as components of a GIS. Thus, D. Sui (pers. commun., November 1993) described a GIS as: “an organized collection of computer hardware, software, geographical data, and trained personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.” The components of a GIS are shown in Fig. 4.

9. Historical

development

resolving power of devices to capture data. Development of relational, and now object-oriented, software for database management have allowed the storage of spatial objects (i.e., geographically referenced points, lines, and polygons) and for linkage of spatial to non-spatial information. Also, research in geographic and information science has effected improved algorithms for analysis of spatial relationships.

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Beginning in the 196Os, rudimentary computerbased geographical information systems began to appear. Because of cost and technical difficulties, early GISs were tailored to solve the specific problems of national and state agencies or large energy companies. One of the first systems was the Canada Geographical Information System, which stored data regarding soils, forestry, wildlife, recreation, and landuse. This system helped analyze the agricultural and recreational suitability of land-use for Canada (Tomlinson, 1988). The first GIS in the United States was developed by the US Forest Service during the early 1960s. Known as MIADS, this system analyzed forest recreation alternatives and hydrology (Parent, 1988). Also during the 1960s oil exploration and production companies began to utilize computer systems for storage and analysis of geological and geophysical data (R. Clemons, pers. commun., June 1992). Contemporaneous with these developments, pioneering computer mapping research was underway in university labs. For example, the Laboratory of Computer Graphics at Harvard developed an automated map analysis system (Parent, 1988). Methodological developments in the 1960s and 1970s laid a foundation of geographic computing techniques for the commercial marketing of GIS. During the last fifteen years, GIS has been transformed from the realm of customized systems designed for specific problems to commercial systems that are general purpose “toolboxes” for acquisition, manipulation, analysis and display of spatial information. This transformation, in part, can be traced to improvements in the computing hardware and software technologies. Significant advances occurred in micro-circuitry of central processor units and in the

The equipment needed for GIS is a computer platform (i.e., central processing unit, visual display unit, magnetic disk drives) and input-output devices (i.e., digitizer, scanner, and plotter). Computer platforms with ample processing speed and data storage space are critical to the success of a GIS. Because of decreased cost and performance improvements in the central processing unit and disk storage, centralized mainframe computing has been replaced by distributed computing systems that usually are a combination workstations, PCs, and graphic terminals. GIS functions (data entry, storage, manipulation, analysis, and display, and output) are automated with software. Software provides an ordered list of instructions that tell the various hardware components how to handle data. Both private and public domain GIS software packages are available (e.g., Arc/Info’, SPANS @, Intergraph”, IDRISI @, GRASS, MAP II”, TIGRIS@). Geographic Information Systems have historically been divided into two categories depending upon the way data are stored, manipulated, and/or analyzed. These categories are raster-based and vector-based (Figs. 5 and 6). R ecent improvements in commercial designs have merged both raster and vector data structures into one system. However, when one considers data structure, an independent discussion of vector and raster formats remains appropriate. Imagine a map over which a grid is placed with each grid cell representing a specific location. The information contained within each cell is referenced by its geographic coordinates when stored and manipulated by the computer. The information in a grid cell represents an average or the dominant character-

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Fig. 7. Conversion Link#

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istic is used to represent the cell (Fig. 7). Also, a presence/absence and mid-point selection criteria can be used to determine the value of a cell. For example, if we placed a grid over a geologic map, and we had a grid cell which consists of l/4 granite and 3/4 sandstone, the cell would be represented and stored as sandstone. This example also illustrates columns 12345678 L 2 3 4 5 6 7 8

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of spatial data from vector to raster format.

the importance of scale in the GIS. If we used a grid with a smaller cell size, the previously mentioned cell might be divided into four cells and provide a more precise representation of reality. In the rasterbased system, a point is represented by a single cell, a line is represented by a series of adjacent cells, and a polygon is presented by a series of contiguous cells. A hybrid of the grid process described above is the quadtree data structure. A quadtree represents spatially distributed “real world” objects using a hierarchical raster structure (Fig. 8). An image or map is progressively subdivided into four quadrants until the desired level of detail in obtained. In this process, areas on the map or image are subdivided until they are composed of a homogeneous class. For example, steep-gradient elevation data will be represented with small cells, referred to as quads, whereas flat terrain will be captured with higher level quads.

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10.2. Data The term geographical data refers to the process of referencing data to a particular location or address. The distinctive characteristic of a GIS is the ability of the system to provide a unique reference address for all data. All locations on Earth, whether land or water, have a unique location and consequently a unique address. These locations are addressed or referenced to a spherical grid system (for example, latitude and longitude). The process of linking data to a geographical location is known as georeferencing. Thus, data can be captured, stored, updated, manipulated, analyzed, and displayed relative to geographical locations. Information associated with a specific location is known as attribute data. For example, we could enter geology as an area data layer in a GIS. Through lab testing, we could determine physical properties (i.e., specific gravity, color, hardness, bearing strength, rip ability, etc.) for different lithologies. These values could be entered into

10.3. Capture and storage process Data can be entered into the GIS program through a variety of methods. Alpha/Numerical data can be entered through the use of a standard keyboard or a tape drive, a CD-ROM, or via an electronic network. Data from maps can be entered by digitizing or scanning. Digitizing is accomplished by placing a map or photographic image on a special tracing table that has an electronic sensitive grid embedded in its surface. The “tracing pen” is sensitive to the electronic grid. Points, lines and areas are “traced” from the map, converted to electronic signals, and transmitted to the computer. Visual data, both maps and photographs, can be entered by scanning. This pro-

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the GIS and referenced to a specific location as attribute data. A GIS can use a wide variety of data types as input. Data are stored and manipulated in a GIS by location (x, y), attribute (z), and time (t) (Fig. 9). Typically data sources might include maps, remotely sensed images, and survey data. For example, elevations, reflectance values from a LANDSAT image, rock type, coastal processes, weathering rates, glacial deposits, faults, slope and aspect are a few types of data which have been used in a GIS (Soiler and Stone, 1987; Mills, 1989; Yassin et al., 1992). Additional data themes could be tectonic structures, geomorphic phenomena, and soils.

In the vector-based system, spatial data are represented by a series of x, y coordinate pairs. A point is represented by a single x,y pair or a node, a line is composed of a series of x, y coordinate pairs, and an area is represented by a series of lines connected to form a polygon. The vector-based system represents mappable features such as points, lines, and area boundaries precisely.

Spatial Objects

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Fig. 9. Geomorphic applications needed for a four dimensional GIS. Knowledge associated with time are essential elements of geomorphic research.

of spatial coordinates

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cess involves passing the map, image, or photograph through a machine which uses a light-sensitive head to capture the image. This sensitive head can detect differences in color or gray tones. The location of every difference is recorded relative to an x-y coordinate system. One of the major strengths of a GIS is the ease with which data can be updated. Data layers can be added, removed, and/or changed. The updating of spatial data can be accomplished through scanning or digitizing, whereas updating of attribute data can be accomplished with the computer keyboard or with a database manager. Data which are entered into the GIS are converted and stored as digital data. These data can be stored on floppy disks, hard drives, magnetic tapes, and CDs. 10.4. Manipulation

and analysis functions

The strength and future potential of the GIS exists in its analytical functionality. The data manipulation and analysis components provide a “toolbox” of functions to transform thematic map data. The ma-

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nipulation and analysis either add value to the spatial database or solve spatial problems. The added value may come from the creation of new thematic maps or visualizing spatial distributions. Spatial problems are solved using measurements of objects in space, by determining spatial relationships, and by creating predictive spatial models. Data within the GIS can be manipulated in a variety of ways. The storage of data in digital form in the GIS facilitates the use of arithmetic operators to manipulate georeferenced data. Data can be grouped; data on one layer can be added, subtracted, multiplied, or divided by data on another layer to produce new layers. For example, a layer showing geology can be combined with a slope map to produce a resultant map showing potential foundation problems. In the geology layer, more competent lithologies could be represented with a low value, whereas claystone and mudstone could be represented with high values. Values on the slope map could be directly related to steepness; the steeper the slope the higher the value; the flatter the slope, the lower the value. Thus, by combining the geology

Map Overlay Map Generalization / Simplification

Spatial Query / Browsing

Measurement

Summary

1

Spatial Reasoning

Spatial Statistics

P [ Al [AZ, A31 = 0.85

L

Analysis of Spatial Relationships

Fig. 10. Typical spatial data manipulation

and analysis functions possible using a GIS.

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layer with slope will produce a map showing the addition of the two layers. High numbers will show areas susceptible to slope movement. Areas with low values would indicate areas of stability. Georeferenced data can be analyzed in various ways with a GIS. As just discussed, manipulation is, in a sense, an analysis of data. Many GIS packages provide for the modeling of data. The analysis process allows the researcher to pose questions that can by querying. For example, a rebe “answered” searcher might want to know “do springs exist within a certain distance from faults?” By overlaying the tectonic layer with surface hydrology, the spatial relationship between faults and springs can be analyzed. Whereas this is a rather simplistic example, the GIS offers the opportunity for high level spatial modeling, one of the fastest expanding areas of GIS research.

relationships that exist between and within thematic maps. The spatial relationship between objects can be analyzed by measuring such parameters as proximity, distance, and trend. Spatial reasoning in some systems provides for decision-making, incorporating both spatial information and heuristic knowledge. Human deductive reasoning can be imitated using expert systems techniques. The simplest systems use rule-based reasoning to interpret within and among geological data themes. GIS technology has improved dramatically in recent years. The suite of analytical tools has been broadened considerably. Further development in statistics for spatial analysis and modeling, however, are needed.

10.5. Display and output

Today, GIS is being used by many disciplines, ranging from geography to geology, geophysics, business, forestry, planning, ecology, wildlife, oceanography, and health. Probably the least appreciated component of a GIS is the personnel. Without appropriately trained and sufficient numbers of people and time, GIS analysis is doomed to fail. Software has become so user friendly that virtually anyone can use and/or misuse it. To acquire appropriate training in GIS, degree programs, primarily offered by geography departments, include B.S., MS., Ph.D. and short courses. As the technique continues to be applied to a variety of disciplines, the number of sources for training will increase.

The typical output from a GIS is a map that can be produced in black-and-white and/or color. The size of the map is dependent upon the type of output device. Maps can be printed with a dot-matrix printer, a laser printer, an ink-pen plotter, or a dye sublimation printer. Map layers can also be displayed via a monitor, either black-and-white or color. Typical spatial manipulation and analysis functions provided by a GIS are: (1) map generalization and simplification; (2) map overlay; (3) query and browse; (4) spatial statistics; (5) analysis of spatial relationships; and (6) spatial reasoning (Burrough, 1986; Laurini and Thompson, 1992) (Fig. IO). These functions are briefly described in the following section. Map generalization and simplification permit reclassification of spatial objects. The procedures allow the user to isolate the specific variables needed for analysis. Map overlay techniques can be used to combine thematic maps. These procedures allow for the synthesis of maps consisting of novel data themes. Whereas the query functions facilitate extraction of information from a spatial database, browse functions permit exploring the contents of a spatial database. With regard to spatial statistics, usually a GIS can provide descriptive statistics and histograms for attributes of spatial objects. Also, a GIS usually provides for correlation analysis to compare spatial

11. Personnel

12. Applications 12.1. Geomorphic

GIS

The use of GIS in geomorphological education and research is expanding. For example, Walsh (1988) described how the GIS can be used by earth scientists and in earth science education. The essence of what a GIS can offer geomorphology is depicted in Fig. Il. The Geomorphic GIS (i.e., Measuring, Mapping, Monitoring, and Modeling) has direct application to both process and Quaternary geomorphology. Giardino and McGrath (1981a, Giardino

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and McGrath (1981b) demonstrated the potential of a primitive raster-based GIS to measure and map geomorphology and natural hazards in the Aspen, Colorado, area. An application of measuring and mapping using a GIS was carried out by Walker et al. (1987). They attempted to assess the impact of oil fields on the northern Alaskan landscape. They mapped general geomorphology, thermokarst, permafrost, and wetlands. Walsh and Butler (1989) used a GIS to map and measure the geomorphic patterns of snow avalanche paths in Glacier National Park, Montana. Through the use of data layers they compared slope aspect with lithology, tectonics, and avalanche morphometry to map spatial patterns of avalanche paths. The GIS is extremely versatile with regards to monitoring. Mills (1989) used a GIS to monitor post-eruption erosion and deposition in the Mount St. Helens’ crater. Chen et al. (1987) used a GIS to monitor changing patterns of soil erosion in a loess dominated drainage basin. We are using GIS in an ongoing study of coastal erosion of Galveston Island, Texas. We have been comparing the temporal and spatial patterns of erosion for the Gulf side and back side of the Island. By querying the data base we can obtain the volume of sediment transported for a specific time period.

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Modeling is undoubtedly the most important process of the GIS. Grunblatt et al. (1992) used a GIS to model desertification processes in East Africa. Gunawan et al. (1994) combined the Land Erodibility Assessment Methodology (LEAM) with a Geographic Information System (GIS) to model land erodibility/soil erosion potential in the tropical rain forests of Sumatra, Indonesia (Fig. 12). Land erodibility was assessed using three major characteristics: (1) slope hazards, (2) rainfall erosivity risk, and (3) soil erodibility. Indices, based on the topography, rainfall, and soil type, have spatial distributions represented on various GIS layers. In Fig. 12A, the raster is placed over the drainage basin and data are entered into the GIS; in Fig. 12B the modeling of the flow of water from cell to cell is shown visually; in Fig. 12C the result of the modeling is shown. The understanding of geomorphic processes from a graded or cyclic perspectives will be enhanced with future developments in scientific visualization.

13. Virtual reality One of the most significant developments in scientific visualization is Virtual Reality (VR). Virtual Reality is a revolutionary modernistic technology

Landscape & Process Modeling

cess

toring

Fig. 11. A Geomorphic

GIS can automate mapping, monitoring,

measurement

and modeling of spatial phenomena.

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A. Thematic Mapping of Watershed

B. Raster-based Model of Material Now

C. Upper Seblat Watershed Modeling Prediction Map

Erosion Potential

Fig. 12. Geomorphic modeling of soil erosion potential in Sumatra, Indonesia, using a GIS implementation of LEAM (from Gunawan et al., 1994).

that creates a three-dimensional, visual-simulationcomputer environment, which is enhanced through the impression of movement. Rheingold (1991, p. 16) described the VR experience as “a wrap-around television with three-dimensional programs, including three-dimensional sound, and solid objects that you can pick up and manipulate, even feel with your fingers and hands.” The field of Virtual Reality is expanding exponentially (Fisher, 1990; Rheingold, 1991; Pollack, 1989). Just as maps can visually enhance the spatial and temporal understanding of phenomena, Virtual Reality can add a holographic perception to data comprehension. Today, with much discussion about the application of Virtual Reality to video games, one wonders about the unlimited potential that can be achieved by combining Virtual Reality with GIS. If VR can be used to enhance video games, its use in education and research cannot be far behind. Experiencing VR today is limited to head-mounted displays (HMDs), either electronic-shutter glasses or a “high-tech” helmet. The HMDs are linked to a drive/direction mechanism such as a “joy stick” or a distinctive glove which provides one with the

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ability to move and manage the three-dimensional objectives that are seen. This apparatus allows one to view and examine any phenomenon from different angles, to move the phenomenon, or to move inside the phenomenon to gain a perspective from the inside out. One might ask how can viewing phenomena from the inside out improve GIS? A GIS stores and manipulates data that are stored in the computer numerically and can be manipulated to produce either a two- or three-dimensional map or the phenomenon being studied image. Although might be dynamic in nature, its representation on a map or in an image is static but GIS packages do permit a “fly over” of a digital terrain model or a “walk-through” of a house via a series of images of the floor plans. In order to model change, the GIS must produce a series of maps to compute the rate of change. Visual appreciation and understanding of the rate of change is gained by viewing the series of maps. Unfortunately, this procedure does not give a true three-dimensional feeling for the rate of change. A first approximation of VR has been attempted by Hilde et al. (1991) and Anderson (1992) who used three-dimensional video visualization techniques to picture ocean bottom topography obtained via seismic profiling. They combined individual seismic profiles to produce a three-dimensional model, which facilitated viewing of the model from above or along one of the sides. Although their presentations were very effective in providing a three-dimensional tour through the image, they were not Virtual Reality. Anderson (1994) has refined the first approximation approach of Hilde et al. (1991) to produce three-dimensional models of Mars using Viking Orbiter images. These models produced evidence of an extended period of glaciation in the Elysium Region of Mars. Recently, Giardino and Hoskins (1993) suggested a GIS-VR application to model the dynamic aspects of shoreline erosion associated with rising sea level. They proposed using a GIS to map spatial-temporal changes in shoreline position and then produce three-dimensional models by overlaying the temporal data over digital elevation models. These temporal models could be linked in VR to provide an individual the opportunity to observe and study spatial patterns of erosion and deposition over time. Because geomorphic phenomena are dynamic, they are

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ideally suited to the application of GIS-VR. GIS-VR will become a standard tool for geomorphological teaching and research in the future.

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helped improve the quality of this paper. In addition, we thank Mark V. Vitek of Texas A&M University for drafting many of the diagrams via computer cartography.

14. Conclusions References Solutions to many geomorphic and Quaternary geology research problems are often gained through map analysis. The gradual loss of training about maps and map use in the curriculum of geology majors places current students at a disadvantage in being prepared to function with the spatial manipulation tools of the twenty-first century-computer graphics, GIS, and virtual reality. The ability to input vast quantities of spatial data and related attributes into personal computers has drastically expanded avenues of research on surficial geology. But these tools can only be used effectively if students are knowledgeable of basic mapping concepts: scale, map projections, and generalization. As the knowledge of chemistry and physics took on greater importance in various aspects of geology, numerous courses were added to educate students in these areas. Whereas the spatial distribution of data has always been important to geomorphologists and Quaternary geologists, a revolution has occurred in the treatment of spatial data with very little response in geology curricula to educate students about these techniques. In some instances, pen and ink remain as the important tools for visual display despite the ability of scanners and computer software to convert pencil sketches into first-class illustrations. Because students have been raised with Nintendo@, Sega’, and a host of other video games, geology departments need to recognize that the future in data analysis is GIS and virtual reality before students are lost to disciplines actively incorporating new techniques and technology into the curricula. Access to data and the ability to maximize data analysis are keys to success in the twentyfirst century.

Acknowledgements We would like to thank Dan Sui of Texas A&M University, Mark S. Gregory and David A. Waits of Oklahoma State University for their comments which

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