Maps and Layers Topics Summary, Review Question, and Next… Maps (4) Geogrpahy, KHU, Jinmu Choi Topics Maps (4) Features and Attributes in a Map (5) Layer and Drawing Symbols (4) Drawing Categories and Quantities (5) Classification Methods (3) Raster Data and Their Drawing (5) TIN Visualization (4) Summary, Review Question, and Next… GISProject

Maps The presentation of geographic data The interface between geographic data and our perception An abstraction of geographic data for a particular class of user Now, maps are static or dynamic The creation of informative and aesthetic maps are necessary GISProject

Use of Maps To identify what is at a location To locate where you are, e.g. GPS To identify distributions, relationships and trends, e.g. exploratory analysis To integrate data from diverse sources into common geographic reference To solve spatial problem, e.g. suitability To find a path, e.g. routing To model events, e.g. various simulation Sharing knowledge about our world GISProject

Spatial Relationships in Map Main spatial relationship Adjacency and neighborhood Connectivity Containment Extra information Difference in elevation Relative position GISProject

Map Elements Data frame Surroundings Other map elements Main part that present geographic data Several layers in one frame Several frames in one layout Surroundings Cartographic context such as scale, arrow, legend Other map elements Title, text, pictures GISProject

Display with Discrete Features Feature types Discrete phenomena Continuous phenomena Discrete features Points: geographic features too small to be depicted as lines or areas Lines: too narrow to be depicted as areas Polygons: closed figure with the shape and location of homogeneous characteristics Hwy 101 Lake Well Woods GISProject

Display with Continuous Features Images and Grids Image sources Aerial photographs Satellite images Grid sources Continuous phenomena Sampling and interpolation Raster data type Two-D matrix of cells Resolution based on the cell size GISProject

Display with Surfaces Surfaces The shape of the earth’s surface Sun illumination, elevation, slope, aspect Raster data DEM Cell has elevation value Vector data TIN Node has elevation value GISProject

Attributes for Mapping Type (or thematic) attributes Coded (or nominal) value: numeric value for types Used for the symbol selection Measured attributes Discrete numeric value: countable objects Real numeric value: measured or calculated value Used for the size of symbols GISProject

Display with Attributes Classified attributes Nominal value or Numeric value Color for each class Labeling Descriptive string: name of features Multiple attributes in different tables or database Object identifier for connecting various external attribute tables GISProject

Layers Basic unit of geographic presentation in ArcGIS layout layers Basic unit of geographic presentation in ArcGIS A set of same type geographic features The same data for multiple representations with different attributes or drawing method Editing data automatically updates representations Sharing representation without duplicate data (.lyr file) frame GISProject

Points with Symbols Points with marker symbols Character marker symbol: TrueType font Simple marker symbol: a square or circle Arrow marker symbol: TrueType font Picture marker symbol: Bitmap (.bmp) or enhanced metafile (.emf) Multilayer marker symbol: composite symbol GISProject

Line with Symbols Lines with line symbols Cartographic line symbol Width, color, parallel offset distance, pattern… Hash line symbol Combined with cartographic lines Marker line symbol Use defined pattern Multilayer line symbol Combines other symbols Cartographic line + hash line = railroads GISProject

Areas with Symbols areas with area symbols Simple fill symbol Color, outline style… Line fill symbol More fill pattern with simple fill symbol Marker fill symbol Use defined pattern Gradient fill symbol Blend of two color Picture fill symbol Use of bitmaps of enhanced metafile Multilayer fill symbol Combines other symbols GISProject

Category Symbol with Color Simplest drawing All features with the same symbol Categories by unique value Attribute for an important subdivision of the feature type Unique symbols for each unique value 12 Pole 12 Railroad 12 Residential 1 Pedestal 46 Highway 46 Lake 61 Transformer 69 Canal 69 Park GISProject

Category Symbol with M-att. Categories by unique combined field value Unique combinations of up to three values Vegetation maps can be separated by dominant types E.g. land use and historic district GISProject

Quantity with Color Quantities by color Data type: ratio, interval Continuous phenomena representation Elevation, temperature, amount of resource Color ramp Using a set of graduated color 2.2-6.3 30-49 8.8-9.8 6.3-9.2 50-79 9.8-23.2 9.2-13.4 80-99 23.2-54.1 GISProject

Graduated Symbol Quantities by Graduated symbols Using size of symbol: ordinal data Rank representation for comparison For drawing, Larger symbols first and the smaller symbols afterward City ranks with graduated marker symbol based on the size of population . 1-2 8.8-9.8 0.2-0.4 3-6 0.4-0.6 9.8-23.2 7-9 0.6-0.8 0.8-1.0 23.2-54.1 10-14 1.0-1.2 GISProject

Proportional Symbol Quantities by proportional symbols Using size of symbol: interval or ratio data Exact proportion to the attribute value No categorical and classification values Continuous graduation of symbol size Larger symbols drawn first 1 10 0.1 1.2 45.1 97.3 GISProject

Classification Methods To subdivide attributes by desired criteria Natural breaks To determine natural clusters of attributes Jenk’s algorithm Minimum variance within a class and maximum variance between classes Graduated symbol or color Good to uneven distributions of attributes GISProject

CM (Cont.) Defined interval Equal interval Classes divided by precise numeric increments Decision on the interval will decide # of classes Age distribution, income level, elevation The first and last classes disproportionate feature number Equal interval To divide ranges of equal value intervals (Max-Min)/(# of classes) will decide range All classes are in the same range GISProject

CM (Cont.) Quantile Standard deviation Equal number of features in each class Effective for ranked values Rank of sales performance Ambiguous natural distribution (clusters) Good to linear distribution Standard deviation Fractional deviations from a mean value One, one-half, one-third, one-quarter std. Good to symmetric distributions Population density or accident rates GISProject

Raster Data Data value: Thematic data vs. Continuous data Thematic data : land use cover Classified data or categorical data Continuous data Continuous phenomena: elevation, slope,… # of theme: Thematic data vs. Spectral data Thematic data: a specific theme (phenomenon) Fire, slope, elevation, aspect…. Single band or layer Spectral data: multiple phenomenon Aerial photography or satellite imagery Panchrometic or multispectral bands Scanned Picture No geometry GISProject

Raster with Unique Value Drawing by unique value Land use/cover, soils type, ownership Cell values are discrete spatially Descriptive or numeric attribute The number of unique values (classes) should not exceed 25 3-7 are most efficient water forest residential industrial GISProject

Raster with Graduated Color Drawing by graduated color Cell values are continuous spatially Elevation, slope, pollution contaminants, Population density Denser concentration use darker 1-4 5-8 9-12 13-15 GISProject

Raster with Stretched Color Drawing cells stretched by graduated color Cell values are continuous spatially Spectral value, calculated value, sun illumination angle High Medium Low GISProject

Raster with RGB Composite Drawing by RGB composite Use three bands for each visual channel True color composite Blue color: Blue band, Green to Green, Red to Red False color composite Blue color: Green band, Green to Red, Red to Near Infrared GISProject

TIN Visualization Triangulated irregular network (TIN) Efficient to represent a surface Sampling and interpolations Elements of a TIN Node: point has continuous real value Edge: line connects nodes and separates area Face: area defines a plane, a slope, a direction Normal: perpendicular vector to a face To calculate illumination, aspect, and slope z y x node edge face normal GISProject

Contour and Aspect with TIN Contour with a graduated color ramp A face can have several contour lines Each zone drawn with a color from color ramp Aspect with a graduated color ramp Cardinal direction of the normal of a face N: 0, E: 90, S: 180, W: 270 z 960m 950m x y z normal face aspect x y GISProject

Representation using TIN face normal sun Hillshading Realistic view of a terrain Calculating the angle between the direction to the sun and the normal to a face Brightness of reflected light proportional to the cosine of the angle Lower angle (sun direction), higher value z y x face normal sun GISProject

Summary Map and feature display Map elements Drawing with Symbols Classification Methods Raster Drawing Methods Drawing with TIN data GISProject

Next… Lab: Working with Layers and Layouts Lecture: Structure of geographic data Assignment Read Modeling Our World Ch3. pp. 59-60; Ch 4 GISProject