DOCSLIB.ORG

Heat Maps: Perfect Maps for Quick Reading? Comparing Usability of Heat Maps with Different Levels of Generalization

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Heat Maps: Perfect Maps for Quick Reading? Comparing Usability of Heat Maps with Different Levels of Generalization International Journal of Geo-Information Article Heat Maps: Perfect Maps for Quick Reading? Comparing Usability of Heat Maps with Different Levels of Generalization Katarzyna Słomska-Przech * , Tomasz Panecki and Wojciech Pokojski Department of Geoinformatics, Cartography and Remote Sensing, Faculty of Geography and Regional Studies, University of Warsaw, Krakowskie Przedmiescie 30, 00-927 Warsaw, Poland; [email protected] (T.P.); [email protected] (W.P.) * Correspondence: [email protected] Abstract: Recently, due to Web 2.0 and neocartography, heat maps have become a popular map type for quick reading. Heat maps are graphical representations of geographic data density in the form of raster maps, elaborated by applying kernel density estimation with a given radius on point- or linear-input data. The aim of this study was to compare the usability of heat maps with different levels of generalization (defined by radii of 10, 20, 30, and 40 pixels) for basic map user tasks. A user study with 412 participants (16–20 years old, high school students) was carried out in order to compare heat maps that showed the same input data. The study was conducted in schools during geography or IT lessons. Objective (the correctness of the answer, response times) and subjective (response time self-assessment, task difficulty, preferences) metrics were measured. The results show that the smaller radius resulted in the higher correctness of the answers. A larger radius did not result in faster response times. The participants perceived the more generalized maps as easier to use, although this result did not match the performance metrics. Overall, we believe that heat maps, Citation: Słomska-Przech, K.; in given circumstances and appropriate design settings, can be considered an efficient method for Panecki, T.; Pokojski, W. Heat Maps: spatial data presentation. Perfect Maps for Quick Reading? Comparing Usability of Heat Maps Keywords: heat map; thematic map; user study; generalization with Different Levels of Generalization. ISPRS Int. J. Geo-Inf. 2021, 10, 562. https://doi.org/ 10.3390/ijgi10080562 1. Introduction Academic Editor: Wolfgang Kainz The world of small-scale mapping on the web is constantly evolving. The main aim of such cartographic representations is often to quickly and quite effectively present Received: 6 July 2021 geographical relations of both qualitative and quantitative character. For the latter, different Accepted: 15 August 2021 thematic map types are used, including those already well established, such as diagrams, Published: 18 August 2021 choropleth maps, dot maps, or isolines. In the age of neocartography and Web 2.0 [1,2], new map types have emerged, such as heat maps that allow point data density based on Publisher’s Note: MDPI stays neutral point-to-area estimation to be visualized [3–5]. From the point of view of the classification with regard to jurisdictional claims in of data presentation methods by MacEachren and DiBiase [6], heat maps can be classified published maps and institutional affil- as continuous and smooth maps. The growing popularity of heat maps comes from their iations. attractiveness and ease of creation, using various mapping libraries [5]. Despite being commonly applied, it has not been evaluated whether they are an effective solution as maps for quick reading in a web environment. Similarly, it has not been verified to what extent their level of detail (generalization) is a key issue. Copyright: © 2021 by the authors. Heat maps were imported into cartography from data visualization techniques, similar Licensee MDPI, Basel, Switzerland. to other map types already well established in cartography, such as diagrams, charts, dots or This article is an open access article choropleths [7]. Heat maps are visualizations for the graphical representation of the density distributed under the terms and of spatial phenomena, usually measured in points. De Boer [3] highlights the fact that conditions of the Creative Commons the term itself is not unambiguous; it can denote both the density map (regardless of Attribution (CC BY) license (https:// the method used) and the process of estimation of point-to-surface data (point density creativecommons.org/licenses/by/ estimation). Heat maps are not necessarily connected strictly to geography [8]. They are 4.0/). ISPRS Int. J. Geo-Inf. 2021, 10, 562. https://doi.org/10.3390/ijgi10080562 https://www.mdpi.com/journal/ijgi ISPRS Int. J. Geo-Inf. 2021, 10, 562 2 of 24 ISPRS Int. J. Geo-Inf. 2021, 10, x FOR PEER REVIEW 2 of 25 used in medicine [9], chemistry [10], biology and ecology [11], the social sciences for non- used in medicine [9], chemistry [10], biology and ecology [11], the social sciences for non- spatial data [12], and eye-tracker analysis [13]. In cartography, heat maps can be found in spatial data [12], and eye-tracker analysis [13]. In cartography, heat maps can be found in studies related to the spatial distribution of social issues [14–16], the visualization of routes studies related to the spatial distribution of social issues [14–16], the visualization of for runners and cyclists [17,18], and the analysis of road accidents [19,20]. The popularity routes for runners and cyclists [17,18], and the analysis of road accidents [19,20]. The pop- of heat maps is growing in the age of big data, as is the need for fast and attractive ularity of heat maps is growing in the age of big data, as is the need for fast and attractive visualizations [5,21,22] (Figure1). visualizations [5,21,22] (Figure 1). FigureFigure 1. 1.Selected Selected examples examples of of a heata heat maps maps with with Open Open Street Street Map Map base base maps maps ((A (()A heat) heat map map prepared prepared in ArcGISin ArcGIS Online Online [22], [22], (B) Location History Visualizer [21]). (B) Location History Visualizer [21]). TheThe designdesign of heat maps in cartography cartography ca cann be be considered considered from from various various perspectives: perspectives: mappedmapped data,data, estimationestimation methods, base map, color color scheme, scheme, legend, legend, and—last and—last but but not not least—generalization.least—generalization. InputInput data data are are usually usually referred referred to points,to points, and and less less frequently frequently to lines. to Methodslines. Methods of transition of transition fromsource from source data to data surfaces to surfaces is done isby done estimation, by estimation, usually usually Kernel DensityKernel Density Estimation Estimation or Point/Line or Point/Line Density Dens Estimationity Estimation [17,23 ,[17,23,24].24]. Most Most often, often, heat mapsheat comemaps with come spectral with spectral or hypsometric or hypsometric scales, butscales, single but colors single are colors used are as wellused [ 4as]. well As the [4]. maps As arethecreated maps are for created quick reading, for quick they reading, are not they always are supplemented not always supplemented by a legend, andby a the legend, colors areand self-evident the colors are (red self-evident = more, green (red == less,more, etc.). green Legends = less, canetc.). also Legends be ordinal/interval can also be ordi- and refernal/interval to “low-to-high” and refer values.to “low-to-high” The base maps values used. The for base heat maps maps varyused fromfor heat OpenStreetMap maps vary orfrom Google, OpenStreetMap via satellite or imagery Google, to via highly satellite generalized imagery topographicto highly generalized content—for topographic example, streets—especiallycontent—for example, in printed streets—especially maps [14]. in printed maps [14]. GeneralizationGeneralization plays an important role role in in every every map, map, including including thematic thematic maps maps [25]. [25 ]. TheThe detailednessdetailedness of of heat heat maps maps is isreflected reflected by by the the radius radius of the of thekernel kernel estimation estimation function: func- tion:the higher the higher the radius, the radius, the more the generalized more generalized the map, the and map, the “hot and thespots” “hot are spots” more areblurred. more blurred.Generalization Generalization is crucial, isespecially crucial, in especially non-interactive in non-interactive maps, which maps, cannot which be dynamically cannot be dynamicallyrescaled; this rescaled; factor influences this factor the influences effectiveness the effectivenessof web maps. of There web maps.can be Thereno effective can be nothematic effective map thematic without map simplifying without input simplifying data and input cartographically data and cartographically refining them. Raposo refining them.et al. [26] Raposo underline et al. [ 26the] underlinerole of generalization the role of generalization in thematic mapping in thematic by stating mapping that by “gener- stating thatalization “generalization is ubiquitous is ubiquitousand critical andin all critical cartography, in all cartography, and by corollary and bythat corollary it is an im- that itportant is an importantaspect of the aspect highly of thepopular highly themat popularic mapping thematic currently mapping capturing currently public capturing and publicotherwise and non-cartographer otherwise non-cartographer attention”. The attention”. authors The also authors applied also the typology applied the of general- typology ofization generalization operators operators(for content, (for geometry, content,geometry, symbol and symbol label) and proposed label) proposedby Roth, Brewer, by Roth, Brewer,and Stryker and
Load more

Recommended publications
  • Cartography. the Definitive Guide to Making Maps, Sample Chapter
    Cartograms Cartograms offer a way of accounting for differences in population distribution by modifying the geography. Geography can easily get in the way of making a good Consider the United States map in which thematic map. The advantage of a geographic map is that it states with larger populations will inevitably lead to larger numbers for most population- gives us the greatest recognition of shapes we’re familiar with related variables. but the disadvantage is that the geographic size of the areas has no correlation to the quantitative data shown. The intent However, the more populous states are not of most thematic maps is to provide the reader with a map necessarily the largest states in area, and from which comparisons can be made and so geography is so a map that shows population data in the almost always inappropriate. This fact alone creates problems geographical sense inevitably skews our perception of the distribution of that data for perception and cognition. Accounting for these problems because the geography becomes dominant. might be addressed in many ways such as manipulating the We end up with a misleading map because data itself. Alternatively, instead of changing the data and densely populated states are relatively small maintaining the geography, you can retain the data values but and vice versa. Cartograms will always give modify the geography to create a cartogram. the map reader the correct proportion of the mapped data variable precisely because it modifies the geography to account for the There are four general types of cartogram. They each problem. distort geographical space and account for the disparities caused by unequal distribution of the population among The term cartogramme can be traced to the areas of different sizes.
    [Show full text]
  • Chapter 1. Map Study and Interpretation
    Chapter 1. Map Study and Interpretation 1.1. Maps A map is a visual representation of an area—a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes. Many maps are static two-dimensional, geometrically accurate (or approximately accurate) representations of three-dimensional space, while others are dynamic or interactive, even three-dimensional. Although most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale; e.g. brain mapping, DNA mapping, and extraterrestrial mapping. 1.2. Types of Maps Maps are one of the most important tools researchers, cartographers, students and others can use to examine the entire Earth or a specific part of it. Simply defined maps are pictures of the Earth's surface. They can be general reference and show landforms, political boundaries, water, the locations of cities, or in the case of thematic maps, show different but very specific topics such as the average rainfall distribution for an area or the distribution of a certain disease throughout a county. Today with the increased use of GIS, also known as Geographic Information Systems, thematic maps are growing in importance. A map is a visual representation of an area – a symbolic depiction highlighting relationships between elements of that space such as objects, regions, and themes. There are however applications for different types of general reference maps when the different types are understood correctly. These maps do not just show a city's location for example; instead the different map types can show a plethora of information about places around the world.
    [Show full text]
  • Investigating Adolescents' Interpretations And
    INVESTIGATING ADOLESCENTS’ INTERPRETATIONS AND PRODUCTIONS OF THEMATIC MAPS AND MAP ARGUMENT PERFORMANCES IN THE MEDIA By Nathan Charles Phillips Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Learning, Teaching and Diversity December, 2013 Nashville, Tennessee Approved: Professor Kevin M. Leander Professor Rogers Hall Professor Pratim Sengupta Professor Jay Clayton Professor Cynthia Lewis To Julee and To Jenna, Amber, Lukas, Isaac, and Esther ! ii ACKNOWLEDGEMENTS My dissertation work was financially supported by the National Science Foundation through the Tangibility for the Teaching, Learning, and Communicating of Mathematics grant (NSF DRL-0816406) and by Peabody College at Vanderbilt University and the Department of Teaching and Learning. I feel most grateful to the young people I worked with. I hope I have done justice to their efforts to learn, laugh, and play with thematic maps. Mr. Norman welcomed me into his classroom and graciously gave me the space and time for this work. He was interested, supportive, and generous throughout. The district and school administrators and office staff at Local County High School were welcoming and accommodating, including the librarians who made some of the technology possible. It would be impossible to express how much my life and scholarship have been directed and supported by Kevin Leander and Rogers Hall over the last six years. Their brilliance, innovative thinking, and academic mentorship are only surpassed by their kind hearts and good friendship. I will forever be blessed by Kevin’s willingness to take me on as a doctoral student and for his invitation to join the SLaMily with Rogers, Katie Headrick Taylor, and Jasmine Ma.
    [Show full text]
  • Thematic Mapping Engine
    Institute of Geography - School of GeoSciences - University of Edinburgh MSc in Geographical Information Science 2008 Awarded with Distinction Part 2: Supporting Document Thematic Mapping Engine Bjørn Sandvik This document is available from thematicmapping.org under a Creative Commons Attribution- Share Alike 3.0 License : http://creativecommons.org/licenses/by-sa/3.0/ Thematic Mapping Engine Bjørn Sandvik Table of contents 1. Introduction 5 2. The Thematic Mapping Engine 7 2.1 Requirements .......................................................................................................7 2.3 The TME web Interface.......................................................................................8 2.3.1 User guide .....................................................................................................9 2.3.2 How the web interface works .....................................................................10 2.4 TME Application Programming Interface (API)...............................................13 2.4.1 TME DataConnector class ..........................................................................14 2.4.2 TME ThematicMap class............................................................................15 3. Data preparation 17 3.1 Using open data..................................................................................................17 3.2 UN statistics.......................................................................................................17 3.3 World borders dataset ........................................................................................18
    [Show full text]
  • Compelling Thematic Cartography by Kenneth Field, Esri Senior Research Cartographer
    Compelling Thematic Cartography By Kenneth Field, Esri Senior Research Cartographer Clarity of Purpose ArcGIS Online has opened up the world of mapmaking, supporting You have some great thematic data and you want to share it. Establishing anyone to author and publish thematic web maps in interesting your goal is the first consideration. Without a goal, you won’t have a ways on an unlimited array of topics. This article explores why it is plan to follow. Are you making a map that allows people to interrogate important to think about design when creating thematic maps. data? Do you want to convey a story or a particular message? A recent survey by the author and Damien Demaj identified ex- A goal is more than just mapping an interesting dataset. You have amples of maps that exemplify great design. This survey found that to define what the hook is for your map. Start by asking strong ques- only 23 percent of these maps were made by people with a back- tions of the data. What will readers want to understand about the ground in cartography. Great thematic maps like Charles Minard’s map’s theme? The map is really just a graphic portrayal of the answer map of Napolean’s retreat from Moscow or Harry Beck’s London to a question. It helps establish how you are going to go about de- Underground map were created by an engineer and electrical drafts- signing the visuals to support that goal. A great map should tell an man, respectively. honest story, so don’t employ mapping techniques that distort.
    [Show full text]
  • Thematic Geovisualization of the Data Profile of Kaligesing, Purworejo, Central Java
    ISSN: 0852-0682, EISSN: 2460-3945 Forum Geografi, Vol 33 (2) December 2019: 153-161 DOI: 10.23917/forgeo.v33i2.8876 © Author(s) 2019. CC BY-NC-ND Attribution 4.0 License. Thematic Geovisualization of the Data Profile of Kaligesing, Purworejo, Central Java Sudaryatno*, Shafiera Rosa El-Yasha, Zulfa Nur’aini ‘Afifah Dept. of Geographic Information Science, Universitas Gadjah Mada, Bulaksumur, Yogyakarta 55281 *) Corresponding Author (e-mail: [email protected]) Received: 22 September 2019/ Accepted: 23 Desember 2019/ Published: 27 Desember 2019 Abstract. The scientific field has a variety of purposes, one of which is the presentation of data and information which can be used by other parties to support their decision making. Moreover, the information is presented spatially. This research aims to map the data profile of Kaligesing district to establish the region’s potential through thematic geovisualization of its data profile, such as slopes, land use, livelihoods and population. The primary data were obtained from visual interpretation of remote sensing images to extract land use information, and DEM processing to extract slope information. Secondary data were provided by the Kaligesing district government. In order to build tiered spatial modelling, each thematic map was classified and weighted according to its contribution to the potential of the region. Based on this modelling, each village was given a compilation of weights, which were used as a basis for regional potential analysis. From the results of the thematic mapping, Kaligesing has three villages that have the potential for development in the agricultural, trade and service sectors, supported by the potential of human resources, and the abundant non-residential land available.
    [Show full text]
  • Numbers on Thematic Maps: Helpful Simplicity Or Too Raw to Be Useful for Map Reading?
    International Journal of Geo-Information Article Numbers on Thematic Maps: Helpful Simplicity or Too Raw to Be Useful for Map Reading? Jolanta Korycka-Skorupa * and Izabela Małgorzata Goł˛ebiowska Department of Geoinformatics, Cartography and Remote Sensing, Faculty of Geography and Regional Studies, University of Warsaw, Krakowskie Przedmiescie 30, 00-927 Warsaw, Poland; [email protected] * Correspondence: [email protected] Received: 29 May 2020; Accepted: 26 June 2020; Published: 28 June 2020 Abstract: As the development of small-scale thematic cartography continues, there is a growing interest in simple graphic solutions, e.g., in the form of numerical values presented on maps to replace or complement well-established quantitative cartographic methods of presentation. Numbers on maps are used as an independent form of data presentation or function as a supplement to the cartographic presentation, becoming a legend placed directly on the map. Despite the frequent use of numbers on maps, this relatively simple form of presentation has not been extensively empirically evaluated. This article presents the results of an empirical study aimed at comparing the usability of numbers on maps for the presentation of quantitative information to frequently used proportional symbols, for simple map-reading tasks. The study showed that the use of numbers on single-variable and two-variable maps results in a greater number of correct answers and also often an improved response time compared to the use of proportional symbols. Interestingly, the introduction of different sizes of numbers did not significantly affect their usability. Thus, it has been proven that—for some tasks—map users accept this bare-bones version of data presentation, often demonstrating a higher level of preference for it than for proportional symbols.
    [Show full text]
  • Visualizing Metadata: Design Principles for Thematic Maps
    10 cartographic perspectives Number 49, Fall 2004 Visualizing Metadata: Design Principles for Thematic Maps Joshua Comenetz This paper argues that the best way to transmit metadata to thematic map users is through cartography rather than text notes or digital Assistant Professor means. Indicators such as reliability diagrams, common on maps de- Department of Geography rived from air photos or satellite images, are rarely included on the- University of Florida matic maps based on the census or other socioeconomic data sources. These data not only suffer from an array of quality problems but P.O. Box 117315 also are widely distributed among the general public in cartographic Gainesville, FL 32611 format. Metadata diagrams for thematic maps based on human vari- ables therefore must be clear and concise, so as to be comprehensible [email protected] by the non-specialist. Principles of good metadata diagram creation are proposed, with attention to the balance between clarity and space constraints. Key words: data quality, reliability diagram, thematic map, visualization METADATA DISPLAY etadata should be included on thematic maps for the same reasons they appear on maps of topography or geology: to help users evalu- ate data quality, ascertain whether maps are appropriate for their intended use, and compare them with other maps. Among the most common ways to provide metadata are through text notes or metadata files, but when a map is based on data that vary spatially in quality or source, cartog- raphy is an efficient means of transmitting them. Previous research and published maps indicate that cartographers have essentially four options for the graphic display of metadata (Beard et al.
    [Show full text]
  • 'Pragmatic Pyramid of Thematic Mapping' The
    ‘PRAGMATIC PYRAMID OF THEMATIC MAPPING’ THE FUNCTIONAL RELATIONSHIP BETWEEN MAP COMPILING, MAP READING, AND CARTOGRAPHIC DESIGN Beata Medynska-Gulij, Adam Mickiewicz University in Poznan, Poland, [email protected] Abstract This paper concerns the dependent relationships between map compilation, map reading, and cartographic design with special regard to thematic mapping. The first step is to measure the simple relationship between cartographic practice and map design and present a pyramid of pragmatic thematic mapping. The model contains various types of maps, a range of cartographic principles, and sources of knowledge for map design. When presented as a pyramid, these functional dependencies can refer to a series of pragmatic criteria which relate to the use of thematic maps. INTRODUTION Pragmatic cartography may be understood both in the sense of practical and in a more limited way pertaining to semiotics. According to Morris (1971:45), the pragmatic is the relationship between the sign and the interpreter, and, in particular, the problem of how the intended designation is understood by the perceiver. Freitag (1971) associates the research area of pragmatic cartography with the map’s function as a vehicle of information. Pragmatic cartography is connected first and foremost with map reading. With various methods of using digital maps, the relationship between map and user has broadened its scope, for example by cartographic compilation. Most often, map compilation results in the creation of thematic maps. These represent the distribution of one particular phenomenon, though a thematic map needs topographic information as a basis (Kraak and Ormeling 2003: 36). Thematic maps have topical contents which are graphically- emphasized or highlighted over a basis which has a status of ‘ground’.
    [Show full text]
  • Introduction in 1569, Dutch Cartographer Gerard Mercator Created A
    Introduction In 1569, Dutch cartographer Gerard Mercator created a projection that allowed mariners to chart and follow a course based on a line of constant compass bearing over long distances. A little over three hundred years later, in 1900, German geographer Max Eckert and American geographer J.P. Goode criticized the misuses of the Mercator Projection on world maps for reference and thematic mapping (Scharfe 1986; Goode 1927). Between 1569 and 1900, the use of the Mercator Projection had spread from its intended nautical audience and often had been inappropriately used in reference and thematic mapping. The utilization of the Mercator Projection for reference and thematic mapping is a problem because the Mercator Projection is a rectangular projection with great areal exaggeration, particularly of areas beyond fifty degrees north or south (Greenhood 1964, Robinson 1990, Snyder 1994) . Despite this obvious flaw the Mercator Projection has been and is still widely used for world maps aimed at a general public audience (Dwyer 2017). This article traces how the Mercator Projection spread from nautical cartography to most reference and thematic world maps in western European and United States cartography. As a result, the focus of this research is not on nautical cartography, rather it targets the moments when the projection moves away from nautical cartography and establishes itself into reference and thematic mapping. Examining the rise of the Mercator Projection sheds light on the complexities of mapping, the choice of map projection and the nuances of the role of maps in and throughout history. First, there is a gap in the literature that warrants further assessment of the Mercator Projection.
    [Show full text]
  • Multivariate Label-Based Thematic Maps
    Multivariate Label-based Thematic Maps Richard Brath1 and Ebad Banissi2 1. London South Bank University and Uncharted Software Inc., Toronto, Canada, [email protected] 2. London South Bank University, London, United Kingdom, [email protected] Abstract: The rich history of cartography and typography indicates that typograph- ic attributes, such as bold, italic and size, can be used to represent data in labels on thematic maps. These typographic attributes are itemized and characterized for encoding literal, categorical and quantitative data. Label-based thematic maps are shown, including examples that scale to multiple data attributes, and a large num- ber of entities. Multiple approaches to handle long labels are considered. Position- al and proportional encoding apply attributes to portions of labels for encoding a large number of data attributes or quantitative values. Quantitative evaluation in- dicates label-based thematic maps may outperform choropleth maps for some tasks. Qualitative evaluation provides guidance for design considerations. Keywords: Typography, cartogram, visualization, font attributes 1. Introduction Typography has been used in maps for hundreds of years to encode data into typographic elements such as size, oblique, case, underline, spacing and font- family. Figure 1 shows an example with these many typographic variants. Fig. 1. Portion of map from Stieler’s Atlas of Modern Geography (1909). Labels use variation in case, weight, underlines (dash, solid, double), italics (and reverse italics), spacing and font- family to encode data. Public domain. Draft of paper submitted to ICC2017. Published version available at https://doi.org/10.1080/23729333.2017.1301346 2 However, thematic maps such as cartograms and choropleths represent data on maps typically with non-textual representations, such as changing the color or size of geographic areas.
    [Show full text]
  • Physical Map Political Map Contour Map Thematic
    Types of Maps 3-Part Cards with Definitions physical map political map contour map thematic map physical map political map A physical map shows an area's natural A political map shows boundaries of features such as land forms, bodies of countries, states, or provinces, as well as water, and vegetation. Physical maps use capitals and major cities. color and shading to show the difference between types of land and water forms. contour lines thematic map Contour lines are used to show the rise A thematic map shows patterns in an and fall of elevation on a map. Each area related to a specific topic or theme, contour line is a group of connected such as population, climate, economic, points on a map that are at the same or political data. elevation. Steeper areas the lines are closer together. road map map scale map projection map grid road map map scale A map scale compares the si#e of the A road map shows the major interstates, map with the real si#e of a place. The highways, and roads of a city or state. scale can change depending on the area shown. A map of a state might have % inch e&ual to 1'' miles, while a map of a room might be 1 inch e&ual to 1 foot. map projection map grid A map grid is a pattern of intersecting A map projection shows the curved hori#ontal and vertical lines forming surface of the globe on a flat map using squares used to locate a certain point on the lines of longitude and latitude.
    [Show full text]