INTRODUCTION TO GEOGRAPHIC INFORMATION SCIENCE GEOG 1800 – FALL 2019 LECTURE 11 Chris McGinty, Course Instructor Office Hours: Wednesday, 3:00 PM – 5:00 PM Office: Janet Quinney Lawson (JQL), Room 231 TOPICS 1. Scale 2. Maps and Cartography DREAMSTIME.COM Spatial Autocorrelation Positive (Clustered): Features that are similar in location and SIMILAR in attributes exhibit positive spatial autocorrelation. RESEARCHGATE.NET Negative (Dispersed): Features that are similar in location but DISSIMILAR in attributes exhibit negative spatial autocorrelation. Spatial Analysis The process of examining the characteristics or features of spatial data, or how features spatially relate to one another. ENERGYNC.ORG ESRI.COM Spatial Objects & Dimensionality Geographic elements (models) have topological dimensions which provide a measure of the way elements fill space. How are vector data y represented in a GIS? z x Topology and GIS Rules that describe how geographic elements (objects) interact with each other in space. Elements may Adjacency Containment interact with each Intersection Overlap other through: Proximity Coincident Recall Spatial Association from lecture 2! Spatial Association: Spatial association is the degree to which things (objects) are arranged in (geolocated) in space. - Wikipedia Key Associations: • Proximity – features are near to, within a distance of • Containment – features contain features • Intersection – features overlap • Connectivity – features connect (networks) • Orientation – feature and object direction Spatial Topology Spatial Topology: Class Exercise Answer the following: • How many polygons (Areas) • How many intersections (Points) • How many Lines? Bonus: How many centroids? QUESTIONS? Scale The term scale has several different meanings: 1. The ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground 2. The precision or number of digits to the right of a decimal point in a EXPEDITIEAARDE.BLOGSPOT.COM number (the more precise the data) 1,979.0806 Spatial Resolution Spatial Resolution is: 1. The detail with which a map depicts the location of geographic features 2. The dimensions represented by each cell or pixel in a raster data set JBARISK.COM Spatial Resolution and Scale Data that has a “fine scale” includes increasing amounts of detail (information) than data that is considered “coarse scale”. Scale and Geographic Extent Projects, maps, and datasets that cover a LARGE geographic areas are considered large-scale. Projects, maps, and datasets that cover a SMALL geographic extents are considered small-scale. Map Scale The relationship (or ratio) between distance on a map and the corresponding distance on the ground. Maps are representations (models) of reality. Representing Scale on a Map Scale is represented as a distance conversion in one of three ways on a map: • Graphic • Verbal KRYGIER.OWU.EDU • Representative Fraction Graphical Scale A map element used to graphically represent the scale of a map. Graphical scales can be enlarged and reduced and still retain meaning. Graphical scale may be culture bound (miles vs. kilometers) and is only accurate at the center of the map. Verbal Scale Scale is expressed as a verbal statement on a map and is generally written in standard (local) terms. 1 centimeter = 1 kilometer 1 inch = 1 mile Difficult to utilize without Simple to understand ruler in hand. and express. Representative Fraction The ratio of a distance on a map to the equivalent distance measured on the ground. Generally noted as being unitless 1 : 24,000 thereby making it simple to 1 : 63,360 understand and not culture bound. 1 : 100,000 Must be recalculated if the map is resized. Which is larger? 1/8 1/16 Small Scale vs. Large Scale A large denominator gives a small fraction resulting in a small scale (LESS DETAIL) map showing a larger area. A small denominator gives a large fraction resulting in a large scale (MORE DETAIL) map showing a smaller area. Common Scales http://www.usgstopomaps.com/scale.html More Map Detail Less Map Detail P. BOLSTAD P. BOLSTAD QUESTIONS? Cartography and Map Elements Maps should contain certain features to aid in understanding: • Legend (but you don’t have to call it a “legend”) • Scale (Graphical, Verbal, RF) • North Arrow • Title (Descriptive but not wordy) • Date Map was created or updated • Author or organization MapElements LONGLEY ET AL. Cartography The art and science of expressing, graphically, usually through maps, the natural and social features of the earth. FUTUREFEEDER.COM Early Cartography Babylonian world map created circa 600 B.C., portrays a flat earth circled by water. DAVIS.COM - HENRY Humans used their best judgment to display the world as they understood. Early Cartography What unique features are present in this map? • Oceans • Rivers • Cities & lands • Babylon centric • Rough distances • Mountains Early Cartography: Religious Influences Religion centric maps portrayed the popular (and dominant) beliefs of the world at the time and were used to enforce those beliefs. WIKIPEDIA.ORG • East on top (not North) • Jerusalem centric • Three major land masses • Ocean 1472 A.D. Tripartite World Map (T and O map) Early Cartography: Nautical Charts • Identified critical ocean currents & sea swells • Generally read and left behind for others to use • How does this qualify as a WIKIPEDIA.ORG “map”? – Known features to the users – Displays information for navigation Marshall Islands stick chart, Circa 300 A.D. Early Cartography: Nautical Charts Defined major routes, but had issues with scale, direction, features. GHALNSIELEM.COM Agnese (Maltese islands) map, 1554 A.D..