Understanding GIS. David SmithЧитать онлайн книгу.
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6)Switch back to the List by Drawing Order view by clicking the
7)Add a purple star point near the areas of interest by clicking the Star 4 icon from the Create Feature pane on the right side of the application and then clicking the spot on the map.
Continue searching for park areas
You’ll keep following the river and looking for likely places for a park.
1)Click the Explore button on the Map tab and pan north.
A little farther north, again on the east side of the river, is a medium-density, lower-income area with just one park (Pecan Playground) in the general vicinity. You’d prefer a high-density neighborhood, but since you don’t yet have specific criteria for your analysis, you want to be inclusive rather than exclusive in your assessments. It’s up to you whether to mark this area or not—all that really matters is that you start to gain a sense of the study area.
2)Add another purple star in this area by going back to the Edit tab and clicking the Star 4 icon.
The area opposite Dodger Stadium, on the east side of the river, is medium density, lower income, and park poor, which makes it rich with possibility for a new park site.
3)Add another purple star in this area.
4)Mark any other areas that seem promising to you.
As you navigate around Griffith Park, remember that the yellow line marks the city limits. The areas north and east of the park aren’t part of Los Angeles and shouldn’t be considered. Once you get around this park, you may find fewer likely areas. But remember, there’s no right or wrong answer for this exercise.
5)When you’re finished marking promising locations, zoom to the layer Bright – Point Notes.
6)Save your edits by clicking the Save button
7)When prompted to save all Edits, click Yes.
8)Close the Create Features pane.
9)Return to the Explore tool on the Map tab to stop editing.
10)Close the Lesson1b map and any open tables.
11)Save your project.
12)Continue to the next lesson or close ArcGIS Pro. Save your changes if prompted.
Now that you’ve explored the study area around the Los Angeles River, you will begin to list the data requirements for the project and begin previewing the data that meets your project needs. This data can also help you reframe your problem and park criteria in more detail by replacing general guidelines with hard numbers and thresholds.
1.Tobler, W. 1970. “A Computer Movie Simulating Urban Growth in the Detroit Region.” Economic Geography 46 (2): 234–40.
| Lesson 2 | Preview the data |
YOU NEED THE RIGHT DATA to solve the problem of where to locate a park. You explored the study area in lesson 1. Now you can proceed more systematically. What data do you have? How useful is it? Is there data that you need but don’t have? Has the problem been stated clearly enough for you to know what data you need?
Acquiring, evaluating, and organizing data is a big part of an analysis project. This book doesn’t fully re-create the complexity of the real world, because all the basic data required is provided. But much of the data isn’t project-ready, and that need for further preparation reflects the real world of GIS.
The first thing you’ll do in this lesson is draw up a planning document to help keep your tasks in focus. You’ll use this document to list the guidelines for the new park and translate them into specific needs for spatial and attribute data.
After you itemize your data requirements in general terms (park data, river data, and so on), you’ll take stock of your source data and investigate its spatial and attribute properties. You’ll also familiarize yourself with metadata, which is the data you have about your data. Before you decide to use a particular dataset, you may want to know things such as who made the data, when, and to what standard of accuracy.
Once you have a better working knowledge of your data, you’ll reframe the problem statement. GIS is a quantitative technology: you can’t analyze a problem until it’s been stated in measurable terms. Wherever you find the city council’s guidelines to be vague, you’ll replace them with hard numbers.
Exercise 2a: List the data requirements
You must relate the guidelines for the new park to data requirements for the project.
Open the data requirements table
A table has been made in advance to help you keep track of your requirements. It’s an informal document, but it will still be helpful. You can refer to it as the data requirements table.
1)Open Windows Explorer and navigate to C:\EsriPress\UGIS4\ParkSite\MapsAndMore.
2)Double-click the file DataRequirementsTable.doc to open it in Microsoft® Word.
List the requirements
In this section, you’ll review the city council’s guidelines (refer to “Park guidelines” in lesson 1, under “Frame the problem”) and describe in a general way the data needed to satisfy them. The specifics of choosing datasets are presented in lesson 3.
The first guideline was to find a vacant piece of land at least one-quarter acre in size. You can break this down into three requirements:
•Land parcel
•Vacancy
•Size
The requirement for a land parcel is already listed in the table. You need spatial data representing parcels so that you can see candidate sites on the map.
The second requirement is vacancy, which is a characteristic, or attribute, of a parcel. In a GIS dataset, vacancy is often listed with other descriptions of land use (commercial, residential, industrial, and so on). In general terms then, you’re looking for a land-use attribute.
1)In row 2 of the table, under Attribute Data, type (or write) land use.
The