Chapter 1
- A bit of review because I took GEOG 292
- GIS has evolved from simply making maps to analyzing some of the world’s most pressing issues
- Beginning of chapter focuses some of the creation of GIS mapsÂ
- Framing a question and why we would even create the map in the first place
- Understanding the data that has been collected for the map. Allows you to think and produce a map in a way that the viewer can absorb the information well and possibly think critically about the information.
- This is a part of the âchoose a methodâ phase it talks about in order to adequately show the data.
- Also talks about processing the data and looking at the results. All apart forming the basis of a map.
- Understanding geographic features in a map and how the data plays into that.Â
- Types of features
- Discrete features
- Location, lines, and actual location pinpointed
- Continuous phenomena
- Blanket entire area of mapping-no gaps
- Features summarized by area
- Represents the counts or density of individual features within area boundaries
- Two ways of representing geographic features
- Vector Model: each feature is a row in a table and feature shapes are defined by x,y locations in space
- Raster model: features represented as a matrix of cells in continuous space
- Discrete features
- Map projections and coordinate systems
- All data layers being used should be in the same map projection and coordinate system.
- Ensure accurate results when layers are combined to see relationships
- All data layers being used should be in the same map projection and coordinate system.
- Types of attribute values
- Categories
- Groups of similar things, helps organize and make sense of data
- Ranks
- Puts features in order from high to low. Used when direct measures are difficult or if the quantity represents a combination of factors
- Counts and Amounts
- Show total numbers
- Counts is the actual number of features on a map and an amount can be a measurable quantity associated with a feature
- Ratios
- Show a relationship between two quantities and are created by dividing one quantity by another for each feature
- Categories
Chapter 2
- Better to look at distribution of features rather than individual to gain better understanding
- Different features for different layers
- Cater map towards audience
- Each layer needs geographic coordinates and map features must have a type of category value to identify each easily
- Map features of as a single type must all be using the same symbol
- Easily shows patterns even within the simplest of maps
- GIS is able to put the data, location, and feature types all together in order to make a cohesive mapÂ
- Using a subset of features allows you or the user to narrow down the the category value to something more specific or even make the range more broad
- Mapping features by category can provide understanding on how a place functions
- Features may belong to more than one category, using different categories within the map can reveal different and addition patterns on the data
- Too many categories within the same map is detrimental.Â
- Display no more than seven different categories
- When mapping an area that is large relative to the size of the features, using more than seven categories can make the patterns to hard to determine(map scaling)
- In smaller areas that are being mapped, individual features are easier to distinguish, so more categories will also be easier to distinguish
- Using too few categories can cause important info to be left out
Chapter 3
- People map where the most and least are to find places that meet their criteria and take action or in order to observe relationship between places and data
- To map the most and least you map features based on a quantity associated with each
- Adds an additional level of info beyond mapping the locations of features
- By mapping the patterns of features with similar values youâll see where the most and least are
- You can map quantities associated with discrete features, continuous phenomena, or data summarized by area
- Must keep the purpose of the map and the intended audience in mind in order to help decide how to present the info on your map
- Once you determined what type of quantities you have, need to decide how to represent them on the map
- Either assigning each individual value its own symbol or by grouping the value into classes
- Mapping individual values you present an accurate picture of the data since you don’t group features together
- May require more effort on the part of map reader to understand the info
- To decide which scheme to use, need to know how the data values are distributed across their range
- Create bar chart and set horizontal axis to be attributed values and vertical axis the number of features having a particular value
- Look at outliers closely as they may be result of an error in the database or anomalies based on small data samples or may be completely valid
- Once decided how to classify data values, youâll want to create a map that presents the info to map readers as clearly as possible
- Keep map simple and present only the info necessary to show patterns in data