Intro to GIS Exercise #5 – Symbology and Map Layout / Design IUP ...

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Projection – get in the habit of listing the coordinate system/projection/datum. It may save you job someday. File location – often used within an agency or private workplace, the file location of the final map product is sometimes listed on the map itself. This is a good idea when making maps for technical documents and research reports. For example, you would list the entire Windows Explorer path name: E:\RJH\Service\MWA\MWA_mining_project.jpg This, with your name/initials, will direct others that you work with where the map is in case you are not around and someone needs a copy of it. This is standard procedure at engineering and consulting firms. LOCATOR MAP: Displayed as an INSET map (a smaller map within the layout that shows a larger area and places the main map graphic in a geographic context) is needed when the main map is not easily recognizable. Do you think you need an inset map for this Two Lick Creek Watershed map? Do this by making the map in another ArcMap session, saving it as a .tiff or .jpeg, then inserting it into your layout as a picture. Remember the rules of the visual hierarchy! First let’s look at the population in each municipality. Double click on the name of the ‘munic’ dataset and when the Layer Properties window appears, click on the Symbology Tab. On the right side are the different ways in which the data can be symbolized on the map. For instance, the Single Symbol way simply displays the shape of the spatial data in the data frame view with the options being Fill Color and Outline Color (options vary depending on the type of vector). After Single Symbol is Categories. Symbolizing and displaying as categories is best for data that has some type of qualitative attribute, such as, Land‐cover (grass, impervious, crops, etc.) or Land‐use (agricultural, urban, farm, etc.). Our data set is quantitative, meaning that all of the values of our attributes are numerical and statistical. So, for this exercise, we won’t be using the Categories way of symbolizing. Let’s move on to Quantities: Click on the word and you see that four different options display below the word: 1. Graduated Colors 2. Graduated Symbols 3. Proportional Symbols 4. Dot Density
About symbolizing data to represent Quantity When you want your map to communicate how much of something there is, you need to draw features using a quantitative measure. This measure might be a count; a ratio, such as a percentage; or a rank, such as high, medium, or low. There are several methods with which you can represent quantity on a map— colors, graduated symbols, proportional symbols, dot densities, and charts. Represent quantity using colors You can represent quantities on a map by varying colors, as a choropleth map. For example, you might use darker shades of blue to represent higher rainfall amounts. When you draw features with graduated colors, the quantitative values are grouped into classes and each class is identified by a particular color. You may want to take advantage of a color ramp to symbolize your data. Represent quantity using symbol sizes You can represent quantities on a map by varying the symbol size you use to draw features. For example, you might use larger circles to represent cities with larger populations. When you draw features with graduated symbols, the quantitative values are grouped into classes. Within a class, all features are drawn with the same symbol. You can't discern the value of individual features; you can only tell that its value is within a certain range. Proportional symbols represent data values more precisely. The size of a proportional symbol reflects the actual data value. For example, you might map earthquakes using proportional circles, where the radius of the circle is proportional to the magnitude of the quake. The difficulty with proportional symbols arises when you have too many values; the differences between symbols may become indistinguishable. In addition, the symbols for high values can become so large as to obscure other symbols. Represent quantity using dot densities Another method of representing quantities is with a dot density map. You can use a dot density map to show the amount of an attribute within an area. Each dot represents a specified number of features, for example, 1,000 people or 10 burglaries within an area. Dot density maps show density graphically rather than showing density value. The dots are distributed randomly within each area; they don't represent actual feature locations. The closer together the dots are, the higher the density of features in that area. Using a dot density map is similar to symbolizing with graduated colors, but instead of the quantity being shown with color, it is shown by the density of dots within an area. When creating a dot density map, you specify how many features each dot represents and how big the dots are. You may need to try several combinations of dot value and dot size to see which one best shows the pattern. In general, you should choose value and size combinations that ensure the dots are not so close as to form solid areas that obscure the patterns or so far apart as to make the variations in density hard to see. In most cases, you'll only map one field using dot density maps. In special cases, you may want to compare distributions of different types and may choose to map two or three fields. When you do this, you should use different colors to distinguish between the attributes.
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Page 3: Knowing which toolbar buttons to us
Page 7 and 8: normalizing the data. For example,
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Intro to GIS Exercise #5 – Symbology and Map Layout / Design IUP ...

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