Understanding GIS. David SmithЧитать онлайн книгу.
1-1 defines some of the various roles that a typical GIS operation might establish to accomplish its work.
| Table 1-1. GIS roles | |
| Editors | People who create, update, and correct spatial data and its attributes (statistical and descriptive information). |
| Cartographers | People who make and publish maps and solve information design problems. |
| Analysts | People who query and process geographic data to solve analytical problems. |
| Programmers | People who implement custom GIS functionality by developing scripts and applications for specific procedures. |
| Managers | People who oversee staffing and equipment, database design, workflow, new technology, and data acquisition. |
The central work in this book is analytical. Your main focus will be on using ArcGIS tools and methods to find the most park-suitable land within a study area, but there is preparatory work to do before the analysis proper, and there are results to interpret and present afterward. This book has two goals. One is to present a comprehensive approach to geographic problem solving. We want to help you develop skills, habits, and ways of thinking that will be useful in projects other than this one. The second goal is to teach you how to use ArcGIS Pro software. These goals are mostly complementary. ArcGIS is a big system, however, and it wouldn’t be realistic to try to cover all that it can do in a single book. Our principle has been to teach the software in the service of the project and not otherwise. You’ll delve into many aspects of ArcGIS Pro—editing, modeling, and cartography, among them—but there are other aspects that we won’t use, or will only touch upon lightly, because they aren’t strictly relevant to our needs. We might say (with apologies to Waldo Tobler)1 that everything in a GIS is related to everything else, but some things are more closely related to analysis than others.
Frame the problem
The first step in the geographic approach to problem solving is to frame the problem. What that means, first, is coming up with a short statement of what it is you want to accomplish. For this project, you want to find a suitable site for a park near the Los Angeles River.
Once you have the statement, you can begin to tease out its ambiguities. What factors make a site “suitable”? In this case, the city council has already established a concise and fairly specific set of guidelines.
Park guidelines
1.On a vacant parcel of land at least one-quarter acre in size
2.Within the Los Angeles city limits
3.As close as possible to the Los Angeles River
4.Not in the vicinity of an existing park
5.In a densely populated neighborhood with lots of children
6.In a lower-income neighborhood
7.Where as many people as possible can be served
This list limits the scope of your inquiry, but it’s far from a complete breakdown of the problem. Some of the guidelines are specific, but others are vague. Familiar concepts are sometimes the hardest to pin down. For example, what income level should count as “lower income”? How are the boundaries of a “neighborhood” established? You can’t solve the big problem until you’ve solved the little problems buried inside. Usually, however, it’s not possible to address (or even foresee) all the little problems ahead of time.
Data exploration influences the framing of the problem. Do you have income data on hand? If so, is it for individuals or households? Is it average, median, or total? To the extent that the questions themselves are indefinite (What is lower income? How should it be measured?), the data you have available will help shape the answer.
Analysis also influences the framing of the problem. Given that you want a quarter-acre tract of vacant land, what do you do about adjacent lots? Is there a tool to combine them? If so, does using it have unanticipated side effects, such as a loss of information? Your data processing capabilities (and your knowledge of them) may determine how you define a “one-quarter acre parcel.”
Even the results of an analysis influence the framing of the problem. Suppose, after having carefully defined the guidelines, you run the analysis and don’t find any suitable sites. Do you report to the city council that there’s just no room for a park? More likely, you’ll change some of your definitions and run the analysis again.
Framing the problem, therefore, is an ongoing process, one that will occupy you throughout much of the book.
Exercise 1a: Explore the study area
In this exercise, you’ll get to know the Los Angeles River and its surrounding area with maps and data. At the same time, you’ll learn the basics of working with ArcGIS Pro: how to navigate a map, add and symbolize data, and get information about map features.
Start ArcGIS Pro
Now you’ll open the ArcGIS Pro application.
1)Start ArcGIS Pro by clicking the Start button on the taskbar, and then, on the Start menu, click All Programs > ArcGIS > ArcGIS Pro > ArcGIS Pro.
To open ArcGIS Pro, you must sign in to ArcGISSM Online using an organizational account. Signing in to ArcGIS Online allows you to access and share GIS content with users in your organization as well as publicly with users around the world.
2)Click Sign In.
The application opens with the ArcGIS Pro dialog box.
Create a new project
1)To create a new project, click Blank.
2)Provide a New Project name: LARiverParkSite.
3)Browse to and select the C:\EsriPress\UGIS4 (Understanding GIS 4th Edition) folder as the location to save the new project folder.
4)Click OK.
When the new project opens, there will be a Contents pane on the left, a Catalog view in the middle, and a Catalog pane on the right. For more information on the Catalog pane and catalog view, see http://pro.arcgis.com/en/pro-app/help/projects/the-project-pane.htm.
Creating a project adds a new folder in the UGIS4 folder with the name you gave it, along with some default items, including a new geodatabase and a toolbox.
5)Select the Databases folder in the Contents pane. The Catalog view will be updated to show the items in the folder. Note that LARiverParkSite.gdb was created. This will be the default geodatabase for your project.
6)Select the Toolboxes folder in the Contents pane. Note that LARiverParkSite.tbx was also created