Introduction to ArcGIS for Environmental Scientists Module 1 – Data Visualization Chapter 3 – Symbology and Labeling

3-1 Introduction to ArcGIS Chapter 3 Objectives Definition of a Layer Layer properties for symbols and labels Creating quantitative displays –Classifications Labeling features –Label Manager –Annotation

3-2 Introduction to ArcGIS 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

3-3 Introduction to ArcGIS 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

3-4 Introduction to ArcGIS 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.

3-5 Introduction to ArcGIS 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

3-6 Introduction to ArcGIS Symbology Point Markers – Simple, Arrows, TrueType, Pictures Line Markers – Simple, Cartographic, Hash, Marker Fill Patterns – Simple, Gradient, Hatched Line

3-7 Introduction to ArcGIS Changing Symbols in the Table of Contents Left mouse click opens the Symbol Selector Right mouse click opens the Color Palette

3-8 Introduction to ArcGIS 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

3-9 Introduction to ArcGIS Style References Set of symbols or elements Industry specific –Environmental, Conservation, Water, Wastewater,etc Can create own styles

3-10 Introduction to ArcGIS Display Symbology Default – single symbol for all features Display based on attribute – Categories – Quantities – Charts

3-11 Introduction to ArcGIS 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

3-12 Introduction to ArcGIS Classification Methods Classification groups attribute values Classification Methods – Natural Breaks – Quantile – Equal Interval – Manual – Defined Interval – Geometrical Interval – Standard Deviation

3-13 Introduction to ArcGIS 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

3-14 Introduction to ArcGIS Quantile and Equal Interval Quantile Divides values into equal ranges Good for mapping continuous data Easy to interpret Each class contains the same number of features Good for mapping evenly distributed data Good for comparing areas of similar sizes Equal Interval

3-15 Introduction to ArcGIS Standard Deviation Shows distribution above and below the mean Easily identify outliers

3-16 Introduction to ArcGIS Exclusions and Sampling Exclusions – Eliminate features with “no data” – Eliminate outliers Sampling – Set maximum sample size – Number of records considered in classification

3-17 Introduction to ArcGIS Labels Label features using attribute values Displays dynamically in map document Layer properties – Control placement, size, etc. – Control map scale

3-18 Introduction to ArcGIS Label Properties Set layer features: – Placement properties – Symbol  Color  Style (bold…)  Size and type – Scale Range  Scale labels visible

3-19 Introduction to ArcGIS Label Manager On Labeling Toolbar Access label properties for all layers in active data frame – More efficient

3-20 Introduction to ArcGIS 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 Labels Independent of layer Specific scale range to display labels Right click layer – Properties – Label Tab – Scale Range – set minimum and maximum scale

3-21 Introduction to ArcGIS 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