types of map generalization
Many formulas have been developed for automatically ranking the regional importance of features, for example by balancing the raw size with the distance to the nearest feature of significantly greater size, similar to measures of Topographic prominence, but this is much more difficult for line features than points, and sometimes produces undesirable results (such as the "Baltimore Problem," in which cities that seem important get left out). The Ramer–Douglas–Peucker algorithm (1972/1973) is one of the earliest and still most common techniques for line simplification.  Most of these algorithms, especially the early ones, placed a higher priority on reducing the size of datasets in the days of limited digital storage, than on quality appearance on maps, and often produce lines that look excessively angular, especially on curves such as rivers. As such, it is the essential basis of all valid deductive inference. , The Baltimore phenomenon is the tendency for a city (or other object) to be omitted from maps due to space constraints while smaller cities are included on the same map simply because space is available to display them. Thus, there is always a need to develop new algorithms, particularly those that can take into account the context in which they operate. The grouping of objects has to be logical. A common example is the addition of a bridge symbol to emphasize that a road crossing is not at grade, but an overpass. These conflicts can be reduced to a basic conflict between the need for more data on the map, and the need for less, with generalization as the tool for balancing them. For line features (and area boundaries), Smoothing seems similar to simplification, and in the past, was sometimes combined with simplification. And so the point is to find design strategies that reveal detail and complexity--rather than to fault the data for an excess of complication. There are many cartographic techniques that are used to adjust the amount of geographic data on the map. A conceptual framework … For discrete fields (also known as categorical coverages or area-class maps) represented as vector polygons, such as land cover, climate type, soil type, city zoning, or surface geology, reclassification often results in adjacent polygons with the same category, necessitating a subsequent dissolve operation to merge them. inheritance (object-oriented programming). For example, a multitude of "buildings" can be turned into a single region representing an "urban area" (not a "building"), or a cluster of "trees" into a "forest". Today's cartographers "end up compiling two things: the geographic database, and maps derived from this database" (Morehouse). Hyponyms such as maple and oak are subcategories of the tree hypernym while cruiser and steamer are types of the hypernym ship. Whether done manually by a cartographer or by a computer or set of algorithms, generalization seeks to abstract spatial information at a high level of detail to information that can be rendered on a map at a lower level of detail. Behavioral Contrast and Promoting the Generality of Behavior Change. Lonergan, M., & Jones, C. B. At least three types of features are displayed on large or intermediate scale (including 1:5K, 1:10K, 1:25K, 1:50K, 1:100K, 1:250K, and 1:500K) maps in the form of linear networks, i.e. Roads are human-made structures, and they are generally arranged in order, intersect with each other, and form networks. For example, tree is a hypernym for peach and oak, while ship is the hypernym for cruiser and steamer. (1991). As GIS came up in the last century and the demand for producing maps automatically increased, automated generalization became an important issue for National Mapping Agencies (NMAs) and other data providers. , Although the Baltimore phenomenon occurs more frequently on automated mapping sites, it does not occur at every scale. An iterative displacement method for conflict resolution in map generalization. A political map shows the state and national boundaries of a place. For example, unambiguously discussing the distance between two cities implies a point conceptualization of a city, and using phrases like "up the road" or "along the road" or even street addresses implies a line conceptualization of a road. Match. Generalization in GIS is no longer merely a cartographic task. TYPES OF TOPOGRAPHIC MAP GENERALIZATION...287 of some built and surface relief elements, depending on the size and width of the given objects. Flow map generalization methods aim to obtain a higher degree of abstraction and can be classified into two types: (1) spatial unit-based aggregation, and (2) flow-based aggregation. Buttenfield, B. P., & McMaster, R. B. Simplification tends to make a curved line look angular, while Smoothing tends to do the opposite. The difference is that smoothing is designed to make the overall shape of the line look simpler by removing small details; which may actually require more vertices than the original. Collapse Dual Lines To Centerline. , Also called dissolve, amalgamation, agglomeration, or combine. Combines polygons within a specified distance of each other into new polygons. Generalization was probably the most thoroughly studied aspect of cartography from the 1970s to the 1990s. This operator is different from aggregation because there is no change in dimensionality (i.e. The latter view focuses on the process of generalization. Jiang B., Liu X. and Jia T. (2013), Scaling of geographic space as a universal rule for map generalization.  One could conceive of a map being quantified by its map information density, the average number of "bits" of information per unit area on the map (or its corollary, information resolution, the average distance between bits), and by its ground information density or resolution, the same measures per unit area on the Earth. 1. In the context of creating databases on different scales, two common strategies are the ladder approach and the star approach. Cartographic generalization, or map generalization, includes all changes in a map that are made when one derives a smaller-scale map from a larger-scale map or map data, or vice versa. (2014), Ht-index for quantifying the fractal or scaling structure of geographic features. A common place where this would occur is the cities Brazzaville and Kinshasa on either side of the Congo river in Africa. However, although generalisation is fundamental, … As GIS developed from about the late 1960s onward, the need for automatic, algorithmic generalization techniques became clear. It is a core part of cartographic design. Chrobak T., Szombara S., Kozioł K., Lupa M. (2017), A method for assessing generalized data accuracy with linear object resolution verification, This page was last edited on 30 November 2020, at 23:52. At a large scale, such a symbol may not be necessary because of the different symbology and the increased space to show the actual relationship. Response Generalization is the extent to which the learner can issue a behavior that is functionally equal to the behavior that was taught. Plotting time is often a bottleneck in many GIS applications. This loss of detail should be taken into account when taking measurements such as length, perimeter, or area as these measurements will now contain some amount of error.  Dissolve is a common GIS tool that is used for this generalization operation, but additional tools GIS tools have been developed for specific situations, such as finding very small polygons and merging them into neighboring larger polygons. This is done by taking a detailed database and reducing its complexity depending on the scale size.. Map generalization: Making rules for knowledge representation. Different researchers invented conceptual models for automated generalization: Besides these established models, different views on automated generalization have been established. lines are dissolved into lines and polygons into polygons), and the original and final objects are of the same conceptual type (e.g., building becomes building). This is probably because it fit within both of the major two research trends of the era: cartographic communication (especially signal processing algorithms based on Information theory), and the opportunities afforded by technological advance (because of its potential for automation). For example, a mountain chain may consist of several isolated ridges in the natural environment, but shown as a continuous chain on a small scale the map. Aggregate Polygons. Hence, simplification may reduce a data set by 70% without changing the perceptual characteristics of some features. Exaggeration often necessitates a subsequent displacement operation because the exaggerated feature overlaps the actual location of nearby features, necessitating their adjustment. As larger cities near Baltimore appear on maps, smaller and lesser known cities may also appear at the same scale simply because there is enough space for them on the map. In recent years, the generalization community has seen a resurgence, fueled in part by the renewed opportunities of AI. The generalization process increases the processing speed. A hyponym is a word that is more specific than a than a general term that is related to it. Description; Aggregate Points. In specific cases, that is not difficult, such as counting the total number of features on the map, or the number of vertices in a single line (possibly reduced to the number of salient vertices); such straightforwardness explains why these were early targets for generalization research. 526.028 ISBN 0-582-08062-2 Library of Congress Cataloging-in-Publication Data Map generalization : making rules for knowledge representation 1 editors, Barbara P. Buttenfield, Robert B. McMaster ; foreword by Herbert Freeman. Topographic maps and navigational charts are often representation-oriented. On-the-fly map generalization can be defined as the ‘‘creation, in real time and according to the user’s request, of a cartographic product suited to its scale and to its purpose, from a larger-scale database’’ (Weibel and others 2002, 320). Created by. One of the most popular models, developed by McMaster and Shea in 1988, divides these decisions into three phases: Philosophical objectives, the general reasons why generalization is desirable or necessary, and criteria for evaluating its success; Cartometric evaluation, the characteristics of a given map (or feature within that map) that demands generalization; and Spatial and attribute transformations, the set of generalization operators available to use on a given feature, layer, or map. Political Maps. Test. Political Map. One of the first operators to be recognized and analyzed, first appearing in the 1973 Keates list, selection is the process of simply removing entire geographic features from the map. Instead of throwing out the building information, or trying to render it all at once, we could generalize the data into some sort of outline of the urbanized area of the region. Another early focus of generalization research, simplification is the removal of vertices in lines and area boundaries. Generalization is the act of simplification. When using the typify operator, a new set of symbols is created, it does not change the spatial data. Generalization has always played a significant role in cartography. "The ScaleMaster Typology: Literature Foundation". An example would be to take a land cover layer with 120 categories, and group them into 5 categories (urban, agriculture, forest, water, desert), which would make a spatially simpler map. A generalization of a concept is an extension of the concept to less-specific criteria, in other words, it is the abstraction of data to a smaller scale . Weight-setting and quality assessment in simultaneous graphic generalization. Progress in studies on automated generalization of spatial point cluster. Within the digital environment, a significant, if not the dominant, control on the graphic output is the role and effect of cartographic generalization. Biffbought a Saturn and it runs well. They are useful for guiding map makers and helping map users understand how maps work. Generalization as a general human activity is first considered in a broad context and map generalization is defined as a special variant of spatial modelling. For example, if Sally learned to pick up a phone and talk on it with a friend, she has response generalization if she can also pick up a walkie talkie and use it to talk to a friend. This is one of the least commonly listed operators.. The generalization tools in the toolset are grouped into three categories: Aggregating zones of data (Nibble, Shrink, Expand, Region Group, and Thin), smoothing data edges (Boundary …  In the first, most conceptual phase, McMaster and Shea show how generalization plays a central role in resolving the often conflicting goals of Cartographic design as a whole: functionality vs. aesthetics, information richness vs. clarity, and the desire to do more vs. the limitations of technology and medium. Owing to the complexity of this particular map type, the process of geological map generalization has not been comprehensively addressed, and [...] The success of automated generalization relies on translation of human knowledge of manual generalization techniques into explicit rules and logic, so that they can be coded in computer language . GIS Lounge, 30 November 2014. This kind of generalization versus specialization (or particularization) is reflected in the mirror of the contrasting hypernym and hyponym word pair. It is then argued that in computer-assisted generalization, the spatial modelling process can be simulated only by strategies based on understanding and not by a mere sequence of operational processing steps. 3. For example, if the objective was to thin out details for a map which would be at a scale of 1:250,000, the cartographer would first start at 1:24,000 and generalize details there. McMaster, Robert B. Typify is a symbology operator that replaces a large set of similar features with a smaller number of representative symbols, resulting in a sparser, cleaner map. For a detailed explanation of each type of operations, see section on generalization operations in cartographic generalization. This results in significant savings in memory. By displacing both of them away from the river (and away from their true location) the symbol overlap can be avoided. They are both the capital city of their country and on overview maps they would be displayed with a slightly larger symbol than other cities. Over the decades of generalization research, over a dozen unique lists of such generalization operators have been published, with significant differences. Pannekoek) 'I.. .the design factor in generalisation. The generalization process reduces storage size. During the first half of the 20th century, cartographers began to think seriously about how the features they drew depended on scale. Eduard Imhof, one of the most accomplished academic and professional cartographers at the time, published a study of city plans on maps at a variety of scales in 1937, itemizing several forms of generalization that occurred, including those later termed symbolization, merging, simplification, enhancement, and displacement. The smoothing principle is also often used to generalize raster representations of fields, often using a Kernel smoother approach. (2003). In the words of Edward Tufte,.  Cartographic generalization or any mapping practices in general is essentially to retain the underlying scaling of numerous smallest, a very few largest, and some in between the smallest and largest. By generalizing you can consolidate data and portray the most important information. The star-approach describes the derived data on all scales is based on a single (large-scale) database. This is the case of stimuli that occasion novel responses. Scale would thus be proportional to the ratio between them, and a change in scale would require the adjustment of one or both of them by means of generalization.  As analytical approaches to geography arose in the 1950s and 1960s, generalization, especially line simplification and raster smoothing, was a target of study.. Maps cannot convey every detail of the real world, so cartographers must decide what information is needed to convey their message. As a map is always at a smaller scale than the phenomena it represents, the elements it contains must be restricted by what can be presented graphically at map scale. This notion of far more small things than large ones is also called spatial heterogeneity, which has been formulated as scaling law. In this way, every map has, to some extent, been generalized to match the criteria of display. Weibel and Jones came up with two terms to distinguish two types of generalization tasks: database generalization and cartographic generalization. The generalization of thematic map types, including categorical maps (e.g., geological, soil, or land use maps), has received less attention, perhaps since categorical maps contain polygons of potentially arbitrary shapes and sizes, rendering them more complex than typical shapes found, for instance, for buildings on a topographic map. It reduces the density of features while still maintaining its relative location and design. Hyponyms such as maple and oak are subcategories of the tree hypernym while cruiser an… Conversely, a hyponym is a term that has a type-of relationship with a hypernym. Harrie, L. (2003). For proper interpretation, the map reader must be aware that because of scale limitations combined elements are not perfect depictions of natural or manmade features. (Eds.). p. cm. That way there is only one record to update when that feature changes in the real world. Gravity. A hypernym is superordinate to a hyponym, and a hyponym is subordinate to a hypernym.  By the late 1980s, academic cartographers were thinking bigger, developing a general theory of generalization, and exploring the use of expert systems and other nascent Artificial intelligence technologies to automate the entire process, including decisions on which tools to use when. 1. It is important to remember that after generalization has taken place, detail is lost. In fact, there are multiple reviews comparing the lists, and even they miss a few salient ones, such as that found in John Keates' first textbook (1973) that was apparently ahead of its time. For example, we might have the outlines of all of the thousands of buildings in a region, but we wish to make a map of the whole city no more than a few inches wide. It is a foundational element of logic and human reasoning. A hypernym is a term that generalizes a class or group of equally-ranked items, or a word that more specific words would fall under categorically. Generalization has a long history in cartography as an art of creating maps for different scale and purpose.  Aggregation differs from Merging in that it can operate across dimensions, such as aggregating points to lines, points to polygons, lines to polygons, and polygons to polygons, and that there is a conceptual difference between the source and product. A political map does not show topographic features like mountains. Generalization as a general human activity is first considered in a broad context and map generalization is defined as a special variant of spatial modelling. Depending on the scale of the map the symbols would overlap. These operations include content operations, geometry operations and symbology operations. Frequently, a Map symbol is applied to the resultant geometry to give a general indication of its original extent, such as point diameter to represent city population or line thickness to represent the number of lanes in a road.  Some of these operations have been automated by multiple algorithms, with tools available in Geographic information systems and other software; others have proven much more difficult, with most cartographers still performing them manually. Web. Using a simple attribute of real-world size (city population, road width or traffic volume, river flow volume), while often easily available in existing GIS data, often produces a selection that is excessively concentrated in some areas and sparse in others. Understanding how to use and apply hypernyms and hyponyms can greatly assist with generalization in cartography. The concept of generalization has broad application in many related disciplines, sometimes having a specialized context-specific meaning. Keywords: On-the-fly maps generalization, Agent, Genetic Algorithm, topological relationships, Ribbons, Visual acuity, Scale. This addition may seem counter-intuitive if one only thinks of generalization as the removal of detail. Several broad approaches to generalization were developed around this time: There are far more small geographic features than large ones in the Earth's surface, or far more small things than large ones in maps. Chicago, University of Chicago Press, 176 p. (ISBN 0-226-53415-4)", "The ScaleMaster Typology: Literature Foundation", "Scaling as a design principle for cartography", https://en.wikipedia.org/w/index.php?title=Cartographic_generalization&oldid=991614734, Articles with unsourced statements from August 2016, Articles with unsourced statements from December 2017, Creative Commons Attribution-ShareAlike License.  Designing a map to achieve the desired gestalt aesthetic is therefore about managing the apparent information density more than the actual information density. Keywords: conﬂict removal, scale reduction, search algorithms, gradient descent, simulated annealing, trial positions 1. there are instances of concept A which are not instances of concept B. Roth, R.E., Stryker, M., Brewer, C.A. Weibel, R and Dutton, G. "Generalising spatial data and dealing with multiple representations. Keates (1973) was one of the first to use the modern terms for exaggeration and displacement and discuss their close relationship, but they were recognized as early as Imhof (1937), This is the addition of symbols or other details on a smaller scale map to make a particular feature make more sense, especially when such understanding is important the map purpose. ", Ross, Kevin. There are many cartographic techniques that are used to adjust the amount of geographic data on the map. A map with a strong visual hierarchy (i.e., with less important layers being subdued but still present) carries an aesthetic of being "clear" because it appears at first glance to contain less data than it really does; conversely, a map with no visual hierarchy, in which all layers seem equally important, might be summarized as "cluttered" because one's first impression is that it contains more data than it really does. Ideally all of the following constraints are present: purpose of map, map for mat, scale, intended audience, data quality, and graphic limitations. (2001). The cartographer has license to adjust the content within their maps to create a suitable and useful map that conveys spatial information, while striking the right balance between the map's purpose and the precise detail of the subject being mapped. There is a toolset in the Spatial Analyst toolbox in ArcGIS that allows for several different methods of generalization on raster data. PLAY. This measurement is further complicated by the role of map symbology, which can affect the apparent information density. There is recent work that recognizes the role of map symbols, including the Roth-Brewer typology of generalization operators, although they clarify that symbology is not a form of generalization, just a partner with generalization in achieving a desired apparent information density.. Thus, cartographers often filter them using their degree of regional importance, their prominence in their local area rather than the map as a whole, which produces a more balanced map, but is more difficult to automate. (the generalization is based on a nonrandomsample of 3 … Some of these operations have been automated by multiple algor… , Perkal, Julian (1958) "Proba obiektywnej generalizacji,", "Das Siedlugnsbild in der Karte (The Settlement Plan on the Map)", "Measuring maps graphical density via digital image processing method on the example of city maps", "Clutter and Map Legibility in Automated Cartography: A Research Agenda", "A typology of operators for maintaining legible map designs at multiple scales", "Mastering map scale: balancing workloads using display and geometry change in multi-scale mapping", "[Review of] Monmonier, Mark (1991) How to Lie with Maps. Jiang B. and Yin J. Automated, continuous map generalization is the focus of this discussion paper. Write. One challenge with the information theory approach to generalization is its basis on measuring the amount of information on the map, before and after generalization procedures. Each option can be relevant at different times. vital role in assessing the overall utility of both computer-assisted map production systems and geographic information systems. If there is an optimal amount of information for a given map project, then generalization is the process of taking existing available data, often called (especially in Europe) the digital landscape model (DLM), which usually but not always has a larger amount of information than needed, and processing it to create a new data set, often called the digital cartographic model (DCM), with the desired amount.. Ideally, agencies responsible for collecting and maintaining spatial data should try to keep only one canonical representation of a given feature, at the highest possible level of detail. 9 Types of Generalization. Creates polygon features around clusters of proximate point features. The estimation of map content priorities has to be adapted to the mapscale and to the intended purpose. A hyponym is a word that is more specific than a than a general term that is related to it. Exaggeration is the partial adjustment of geometry or symbology to make some aspect of a feature larger than it really is, in order to make them more visible, recognizable, or higher in the visual hierarchy. Definition Map generalization is the name of the process that simplifies the representation of geographical data to produce a map at a certain scale with a defined and readable legend. I guess Saturns arereliable cars. Many general conceptual models have been proposed for understanding this process, often attempting to capture the decision process of the human master cartographer. This operator primarily simplifies the attributes of the features, although a geometric simplification may also result. Imhof (1937) discusses these particular generalizations at length. There are numerous sets of cartographic design principles. A political map … Unlike the aggregation operator which replaces many related features with a single "group" feature, the symbols used in the typify operator still represent individuals, just "typical" individuals. , Displacement can be employed when two objects are so close to each other that they would overlap at smaller scales, especially when an exaggerate operator has made the two objects larger than they really are. Depending on whether you are generalizing vector or raster data, there are different tools for generalizing GIS data using ArcGIS.
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- types of map generalization
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