Chapter 1 Introducing ArcGIS: Navigation, symbolizing, labeling, 2D / 3D Maps
1.1
Feature Class: The basic building block for displaying graphic features on a map. They are vector data with corresponding attributes for each feature.
Raster Dataset: A major type of spatial data that creates a raster, an image made up of pixels. A good example is satellite imagery.
File geodatabase: A folder with the extension .gdp that stores feature classes, raster datasets, and other related files.
Basemap: A layer that helps orient users to a location. Additional feature classes are placed on top of a basemap to provide specific information for visualization, analysis, or problem solving.
1.2
- You can search for features using attribute values, such as the name of a street.
- Some feature classes can be set to be seen only when zoomed to a certain scale
- You can access preset locations and scales using spatial bookmarks
- You can read the attribute data of any feature by clicking the feature to show a pop up
1.3
- Attributes allow you to search for useful information and mapped features
- You can change the order of attribute columns in a table, change the names, see the data type of attributes, delete attributes, and make only certain attributes visible in the Fields of View menu
- Press and hold shift with the selection tool on to select any subset of points. Hold shift and click to select one more multiple, hold control to deselect.
- The summary statistics tool can compute maximum, minimum, mean, and SD and writes the results on a new table
1.4
- Symbols of feature classes can be changed by color, size, and shape
- Features can be labeled with different fonts with added halos for improved readability
- The contrast in population density within an urban area is difficult to appreciate using color symbology. 3D makes an impressive difference.
Chapter 2: 3D maps, dot density maps, visibility ranges, point symbols, symbolizing maps
2.1
- Thematic map: Consists of a subject layer or layers placed in spatial context with other layers, such as streets and political boundaries. TO choose layers for a thematic map, ask the questions “What layer or layers are needed to represent the subject” and “what spatial context layers are needed to orient map users to recognize locations and patterns of subject features?”. Often, but not always, the subject of thematic maps are vector layers (points, lines, or polygons)
- An overall goal of thematic maps is to make the subject prominent while placing spatial context layers in the background
- Lighter colors help reduce distraction and clutter, especially with border colors
2.2
- Two forms of text in ArcGIS are labels and pop-ups.
- Functions for labeling are a little spread out between different tabs and access points, a little confusing to remember where all are located.
2.3
- A definition query cam limit the features displayed to a desired subset of the larger collection, based on the values in the feature attribute table
- A definition query is different from “Select By Attribute (ch.1)” because it is used to filter the features of a layer rather than select a temporary subset to work with. They both have a similar SQL (Structured Query Language) interface
- Find Definition Query under right clicking the feature and selecting properties
- Using an ‘Or’ connector makes a compound condition, so any record satisfying one of the two simple conditions will be displayed. If ‘and’ was used instead, no records would be selected because a facility cannot have more than one code value.
- Different shapes for symbology are important for users with color blindness or still being able to be distinguishable in black and white copies
- Figure features are brightly colored and ground features are shades of grey
2.4
- Numeric elements attributes should be broken into relatively few classes of roughly 3-9.
- To symbolize map features, you need only the sex of maximum values for the class, called break points. The minimum value is included in the class, but the maximum goes in the next classification.
- A choropleth map uses color in polygons to represent numeric attribute values, generally increasing in darkness of color where shade would represent increasing value.
- Classification methods are used to display choropleth maps, and the default method is Natural Breaks (Jenks), which uses an algorithm to cluster values of the numeric attributes into groups, with boundaries of the groups (break points) defining classes
- The Quantile method is easily understood and provides information about the shape of a distribution. It breaks a distribution into classes, each with the same percentage of data points. For example, quantiles with 4 classes each have 25% of the data observations
- Other methods are the Defined Interval Method (uniform distribution with easily read numbers for break points) and the Geometric Interval method (increasing width interval distribution of break points)
- Many attributes have skewed distribution
- To make a 3D map, select feature layer, go to extrusion group, type, then base height.
2.5
- Graduated and proportional point symbols: Proportionally sized point symbols can display data such as a larger symbol indicating a larger data value
2.6
- Chropleth maps of normalized population data have different uses from those of choropleth maps of population
- Dividing a segment of the population by the total population to provide info about the makeup of an area = Normalizing
- Density maps can also be normalized. Dividing population and other variables by their polygon areas, yielding a measure of spatial concentration.
- Geometric Interval Method works well for representing the long tails of distributions skewed to the right, but the breakpoints aren’t easily read
- Comparing a symbology layer through import layer and swipe to compare features can allow a quick visual comparison between datasets
2.7
- Dot density maps can denote quantitative values. An advantage over choropleth maps is that more than one variable can be displayed at the same time using different colored dots
2.8
- GIS uses visibility ranges to automatically turn layers and labeling on and of, depending on zoom level
- Map scale: The ratio of the distance between one point and another on your screen divided by the distance between the same two points in inches on the ground
- Map scale is unitless, as a ratio that divides units. Therefore, you can use any distance unit
- Scale is counterintuitive, similar to SAV ratios. The large number is actually a smaller scale, and the smaller is actually larger.
- Large scale shows feature labels turned on when zoomed in, and off when out. Features can also be turned off when zoomed in.
- Features and labels can have different visibility ranges to reduce clutter
Chapter 3: Maps for End Users: Building map layouts and charts, sharing maps on ARCGIS Online, use MapViewer in ArcGIS Online, Story Maps/Dashboards
3.1
- If making a report, it’s better to keep tables and maps as stand alone figures so they are separate and your layout is simple and clear
- Right click a layout figure, click properties, under elements and placement size, you can change the sizing to be the same as other figures or resize a figure. Under layout, then Map, use Full Extent to make the figure properly fit the new sizing.
- Right click on the ruler to add a guide to place figures at the same boundary lines, and then drag them to the guide boundary lines to ‘snap’ them in place
- ArcGIS will automatically generate and design a legend. Can be found under Insert -> map surrounds -> legend
3.2
- To share/publish a map online, you must change a property of the map. You must also have a basemap layer. Right click the map under contents, click properties and then under general, make sure the ‘allow assignment of unique numeric IDs for web sharing…” is checked
- You can modify map settings on the arcgis website
3.3
- ArcGIS story maps allows you to create stories that include web based interactive maps, text, images, videos, and other content
