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Introduction to ArcGIS for Environmental Scientists Module 1 – Data Visualization Chapter 3 – Symbology and Labeling. Chapter 3 Objectives. Definition of a Layer Layer properties for symbols and labels Creating quantitative displays Classifications Labeling features Label Manager
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Introduction to ArcGIS forEnvironmental ScientistsModule 1 – Data Visualization Chapter 3 – Symbology and Labeling
Chapter 3 Objectives • Definition of a Layer • Layer properties for symbols and labels • Creating quantitative displays • Classifications • Labeling features • Label Manager • Annotation
What is a Layer? • References a spatial data source – Geographic data is not stored in the map document – Stores the path of the data source • Layers can come from a variety of sources – Vector datasets: coverages, shapefiles, geodatabases, CADD files, ArcSDE – Raster datasets: grids and images – Any geographic dataset that you add to your map
Layer File • Saves symbology and other display properties of a data layer • Saved from within the map document • Saved with .lyr extension on local or network drive • Can be used in other map documents
Broken Data Links • Map documents lose track of data location when data are moved or renamed. • Remember data are only referenced in ArcMap. It does not store data. • To repair broken link: 1) Right click on layer name Properties. 2) Click on Source tab Set Data Source. • Shortcut: Right click layer name go to Data Repair Data Source Repairs all data sources in same directory or geodatabase.
Symbology • Feature information conveyed graphically – Color, shape, size, pattern, orientation, etc. – Natural or conventional – Interpreted with map legend • Change symbology in the Table of Contents or Symbology tab in layer properties
Symbology • Point Markers – Simple, Arrows, TrueType, Pictures • Line Markers – Simple, Cartographic, Hash, Marker • Fill Patterns – Simple, Gradient, Hatched Line
Left mouse click opens the Symbol Selector Changing Symbols in the Table of Contents Right mouse click opens the Color Palette
Raster Symbology • Different methods to improve raster display • Change brightness or contrast • Stretch values to enhance contrast • Group data values into classes • Use red–green–blue (RGB) composite • Display using transparency • Create pyramids for faster drawing
Style References • Set of symbols or elements • Industry specific • Environmental, Conservation, Water, Wastewater,etc • Can create own styles
Display Symbology • Default – single symbol for all features • Display based on attribute – Categories – Quantities – Charts
Display Symbology • Quantities – Graduated symbols • Symbol size reflects class – Graduated colors • Symbol represented by colors – Proportional symbols • Symbol size reflects actual data value – Dot density • Each point represents a count • Charts – Display large amounts of data in “eye–catching” fashion – Pie, bar, stacked
Classification Methods • Classification groups attribute values • Classification Methods –Natural Breaks – Quantile – Equal Interval – Manual – Defined Interval – Geometrical Interval – Standard Deviation
Natural breaks • Default method – Jenks Method • Identifies gaps for breakpoints between values • Good for mapping values that are not evenly distributed – Shows clusters or concentrations of values
Quantile Equal Interval Quantile and Equal Interval • Each class contains the same number of features • Good for mapping evenly distributed data • Good for comparing areas of similar sizes • Divides values into equal ranges • Good for mapping continuous data • Easy to interpret
Standard Deviation • Shows distribution above and below the mean • Easily identify outliers
Exclusions and Sampling • Exclusions • Eliminate features with “no data” • Eliminate outliers • Sampling • Set maximum sample size • Number of records considered in classification
Labels • Label features using attribute values • Displays dynamically in map document • Layer properties • Control placement, size, etc. • Control map scale
Label Properties • Set layer features: • Placement properties • Symbol • Color • Style (bold…) • Size and type • Scale Range • Scale labels visible
Label Manager • On Labeling Toolbar • Access label properties for all layers in active data frame • More efficient
Labels • Independent of layer • Specific scale range to display labels • Right click layer – Properties – Label Tab – Scale Range – set minimum and maximum scale Scale Dependency Features vs. Labels Features • Display layers at specific scale range • Reduces clutter, reduces drawing time • Right click layer – Properties –General Tab – set minimum and maximum scale
Convert Labels to Annotation • Convert labels to annotation – Current scale is used – Options for storage • In map document • In annotation feature class • Fixed location – doesn’t move dynamically in display when zoom in and zoom out • Allows user to control placement and/or change the font type for each individual text element