Lab 2: Creating Map Displays Introduction: Choosing how to communicate the meaning of a map may be one of the most important decisions a spatial analyst can make. Composing an effective map requires a component of artistic expression as well as familiarity with proven cartographic norms. A design that is visually pleasing will more easily catch the attention of your audience and give you an opportunity to convey your message. This can be a challenging task. Your goal is to convey concise information about the real world at extremely reduced scales. This can be achieved through the careful use of symbology to represent features on the earth. The table below highlights the various GIS symbol types and their appropriate alterations to aid in effective communication. ESRI, GIS Day Materials For many years cartographers have been studying the science and art of creating effective map layouts. For our purposes, we will focus on a basic set of cartographic principles that includes balance, hierarchy, figure/ground relationship, and visual contrast. Balance is the organization of map elements (data frame, north arrow, scale, etc.) in a fashion that limits the creation of large open spaces on the layout. Hierarchy is the established sequence of importance of the map data elements; care should be taken to assure that the most important elements ‘stand out’ in relation to the others. The figure/ground relationship is the ratio of figure (the to-be studied or important mapped data) to the ground (background or unimportant mapped data); too much of either and the map will begin to lose its meaning. Finally, the visual contrast is set to assure that the elements or objects of your map are distinctly different from the background information. Each of these compositional elements directly affects the legibility, or clarity, of your map. Shape, size, position, hue (color), value (darkness), pattern, and symbology are altered to control the basic design principles. More information about these and other principles of map composition is available online: • The Geographer’s Craft (University of Colorado): http://www.colorado.edu/geography/gcraft/notes/cartocom/cartocom_f.html Under “Section 4. Basic Elements of Map Composition” • Introduction to Map Design (ESRI): http://www.esri.com/industries/k-12/education/~/media/files/pdfs/industries/k- 12/pdfs/intrcart.pdf Page 16 - "Map Composition" • Map Design (Borden D. Dent: Cartography – Thematic Map Design, 5th ed. Ch 13) http://www.geog.nau.edu/courses/rh83/pl431/workbook/MapDesign.PDF Learning Objectives: 1 Lab 2: Creating Map Displays • To understand a set of basic cartographic principles • To explore the tools within ArcGIS that will help achieve those principles • To develop an ability to communicate through maps To be submitted: 1. (10 pts) A write-up answering the questions throughout the lab. Include as many graphics as necessary to illustrate your answers. (500 word maximum, 12pt font, 1.5 spacing) 2. (10 pts) A map layout that adheres to the cartographic principles detailed above. Overview: To explore the concepts of mapping presented in lecture and described above, you will be provided three data sets (roads, land use, & places) for Washtenaw County, Michigan (home to UM). You will prepare a general reference map that displays Land Use and Population Centers (LUPC) in Washtenaw County, following the steps outlined in the lab. The purpose of this map is to provide a general overview of the land-uses in relation to the population centers within Washtenaw County. In addition to providing general reference, you will choose a more specific target audience and purpose for your map. Be sure you are clear about what is to be communicated and adjust the various cartographic elements to achieve this goal. Procedure: 1. Download the lab2 data from Ctools and unzip into your lab2 directory, remember to create a “lab2” directory within your M:\gss777 drive space. Remember: No spaces in file names. 2. Connect to your working directory via ArcCatalog. 3. Add data to ArcMap: With the skills you have acquired from the previous lab, add the Roads (roads_utm), Land Use / Land Cover (land_utm), and Washtenaw Places (wash_places) shapefiles to ArcMap. 4. Defining the appropriate symbology The procedure below details how to set the symbology for the polygon layer, land_utm. You will then be instructed to set the symbology for the line and point layers (roads_utm & wash_places) in a similar fashion. • Right-click on the land-use layer (land_utm) from ArcMap’s table of contents and select ‘Properties’. • Choose the ‘Symbology’ tab; from here you will be able to alter the display symbology for the associated shapefile. • From the ‘Show’ box on the left, select ‘Categories’| ‘Unique values’. This will allow a unique color to be displayed for each attribute label. 2 Lab 2: Creating Map Displays • The ‘Value Field’ selector will allow you to define which attribute you would like the symbology to be displayed upon – choose LAND_USE. Uncheck the <all other values> box and click the ‘Add All Values’ button to fill the symbol column with the available categories from the Land_Use attribute. Select a Color Ramp that you think best represents each land-use category. Click ‘Apply’ and ‘OK’ to continue. • If, upon display in ArcMap, the colors do not logically match the land-use labels or are not distinguishable enough from one another, right or left click on the symbol color in the table of contents and adjust accordingly (try both as they allow different options). By selecting ‘more colors’ at the bottom of the color options window, you can access the HSV sliders, which allow you to change hue while holding value and saturation constant, or change value while holding hue constant. You may also want to alter the symbology color ramp again. • Verify the legibility of your symbology choices in ArcMap. • If you believe there are too many categories or colors being displayed, you have the option to merge the various categories into aggregated groupings (for instance: forested, agricultural/open, residential, commercial, transportation, and hydrology). To accomplish this, return to the symbology tab in Properties, left-click (while holding down the ctrl key) on the symbol for each of the categories to be aggregated, right-click on one of them while all are still selected, and choose ‘group values’, then adjust the label (e.g., forested) to better represent the newly formed class. A few useful tools for designing color schemes: • A user-friendly tool specifically designed for mapping: http://www.colorbrewer2.org • Another useful tool for picking color schemes is the Adobe Kuler website: http://kuler.adobe.com/#themes/rating?time=30 • To see how your colors will be perceived by color blind people: http://www.internettg.org/newsletter/mar99/color_challenged_table.html Or download a free color-blindness simulator: http://color-oracle.en.softonic.com/download Question 1 (4 points): Briefly define the three components of color (hue, value, and saturation). In what situations would it be best to hold value constant and vary hue to differentiate map categories? In what situations would it be best to hold hue constant and vary value to differentiate map categories? How did you come up with a color scheme for your land use categories (which components did you choose to vary and which did you choose to hold constant and why? What other considerations affecting your color choices?) (Note: this should reflect your answer to Q3). Repeat the procedure of adjusting symbology for the roads_utm data. Use IGDS_LEVEL as the attribute based on which to display. Choose appropriate colors and line widths for the road network that will help establish location within the county, but not distract the viewer from the main focus of your map. Set the symbology of the final component of your map, wash_places. For this layer, you are interested in two aspects, location and population; you will need to adjust your symbology to account for both. • Open the ‘Properties’ dialogue for wash_places point and click the ‘Symbology’ tab. 3 Lab 2: Creating Map Displays • From the ‘Show’ box, select ‘Quantities’ | ‘Graduated symbols’. This will allow you to increase the symbol size for the cities as the population grows. • Specify A1990 (Population from 1990) in the ‘Fields Value’ box. • Choose a from/to symbol size for the display. This will set the minimum and maximum size for the symbol graduation in your layout (it may take several selections, viewings, and reselections to find the symbology you are most comfortable with). • Classify the data using Natural Breaks, Equal Interval and Quantile methods. To do this, click on the ‘Classify’ button in the ‘Classification’ box. Select up to 5 classes to break up your data. Completing the table below may assist you in describing the differences between the three methods (for your reference only; do not include this table in your write-up). Classification Method Natural Breaks Equal Interval Quantile Break value 1 Break value 2 Break value 3 Break value 4 Break value 5 • Choose a Classification method and number of Classes that best describes your data. Use the Help system to decide which of these would be most appropriate for you. Select the number of classes you wish to use to break up your data (again it may take several selections, viewings, and reselections to acquire the symbology you are most comfortable with). • Once you have selected a classification scheme, it is usually a good idea to round off the values of each category. Round aggressively to avoid a map legend that has too much detail to be easily read. You can change the value ranges manually by left-clicking on a value range (under ‘Range’ under the Symbology tab) and typing in the upper limit of that range.