Understanding GIS. David SmithЧитать онлайн книгу.
in this book was inspired by the Los Angeles River Revitalization Master Plan (available at http://www.lariver.org). Images from the master plan are used in lesson 1 by permission.
Many Esri employees reviewed the book in whole or in part, tested exercises, and gave advice or help. Thanks to all of them for their skill and dedication.
Thanks to the University of Redlands students who tested and provided valuable feedback on the exercises for this fourth edition. We want to acknowledge the support of the University of Redlands and the Center for Spatial Studies as well as Center for Spatial Studies GIS interns Anyssa Haberkorn, Adrian Laufer, and Jack Hewitt. Special thanks to the students of SPA 110—Introduction to Spatial Analysis and GIS, from the fall 2015 through spring 2017 semesters, who provided valuable constructive feedback on the workbook lessons.
And, most of all, a huge thanks to Clint Brown of Esri for supporting this project through thick and thin.
Required software version
This book requires ArcGIS Pro 2.2 software with an Advanced license. Earlier software versions may not be fully compatible with exercise data and do not operate as described in the exercises.
Data license agreement
Downloadable data that accompanies this book is covered by a license agreement that stipulates the terms of use.
Installing the project data
To install the exercise data, go to the link on the book resource web page.
You will need to read and accept the data license agreement terms.
Accept the default installation folder or navigate to the drive or folder location where you want to install the data. The exercise data will be installed on your computer in a folder called C:\EsriPress\UGIS4 (or \UGIS4 in the folder where you installed the exercise data).
| Lesson 1 | Frame the problem and explore the study area |
THE VOLATILE LOS ANGELES RIVER is the reason that America’s second-largest city was founded in its present Southern California location by Spaniards in 1781. (The area was originally settled thousands of years earlier by the Gabrielino/Tongva Nation, a California Indian tribe also known as the San Gabriel Band of Mission Indians.) Its water was tapped for drinking and irrigation, and a new city spread out from the river across the coastal plain. By the turn of the 20th century, the river was surrounded by a thriving urban center. Every few decades, raging floods would crest the banks at various points, submerging entire neighborhoods. After the historic floods of 1938, which claimed more than 100 lives and washed out bridges from Tujunga Wash to San Pedro (figure 1-1), city leaders had seen enough. By 1941, the US Army Corps of Engineers had begun to straighten, deepen, and reinforce the once wild waterway. Much of its length was eventually lined in concrete, and the river was more or less tamed.
Figure 1-1. The historic floods of 1938 washed out bridges up and down the Los Angeles River, including this one at Colfax Street and Vernon Boulevard.
Today, the City of Angels—home to nearly four million people—is a vibrant world center of business and culture. Running straight through the heart of the city, the Los Angeles River now serves as a flood control channel (figure 1-2). Sadly, this once bucolic waterway that was so instrumental to the formation of the city later became known as something ugly and marginal. Mile after mile of angled concrete appealed only to graffiti artists and filmmakers, and save for the occasional televised rescue of some hapless Angeleno swept away by a winter storm-fed torrent, the river remained a part of the city ignored by most. The negative perception has stuck with the neglected river for decades.
Figure 1-2. The Los Angeles River now serves as a flood control channel though the river corridor is the focus of city regreening efforts.
But in recent years, as the city has densified and much of Southern California’s wild lands have been appropriated for development, new attention has focused on the river corridor and the scattered pockets of open space that line its length. Although it must always serve its important flood control function, the river and adjacent lands are increasingly recognized as underutilized, providing opportunities for regreening and psychic restoration for people living in an overbuilt city. Adventuresome and resourceful citizens have discovered peaceful pockets of sanctuary along the river and made these places their own. A vital and concerned activist community has raised awareness of the river and pushed for its beautification and redevelopment.
In 2005, the city launched a major public works project focused on the human dimensions of the river. A landmark study, the Los Angeles River Revitalization Master Plan, demonstrated the significant potential of redevelopment to improve the quality of life for citizens living near the river corridor. Then mayor Antonio Villaraigosa said at the time, “We have an opportunity to create pocket parks and landscaped walkways . . . to create places where children can play and adults can stroll.”
According to Villaraigosa, “The plan provides a 25- to 50-year blueprint for transforming the city’s 32-mile stretch of the river into an ‘emerald necklace’ of parks, walkways, and bike paths, as well as providing better connections to the neighboring communities, protecting wildlife, promoting the health of the river, and leveraging economic reinvestment.”
Although the 2005 master plan identified some of the most obvious areas for large-scale regional redevelopment along the river, it stopped short of identifying smaller (and more affordable) neighborhood projects; that work would require a more involved study. With thousands of land parcels strung out along the river, identifying the best places for park development is like looking for a needle in a haystack. Many factors come into play, among them current land use, demographics, and accessibility.
In the years since the plan’s completion, the city has created a website (figure 1-3) that encourages people to learn about (and participate in) the latest developments related to its landmark resource. The website, at www.lariver.org, contains links to many resources about the river and its watershed, including scientific studies and recreational opportunities. If city leaders can find the resources and a motivated citizenry keeps up the pressure, a renaissance will transform growing stretches along the river into real versions of the revitalization effort’s artists’ renderings (figure 1-4).
Figure 1-3. The Los Angeles River Revitalization website contains links to information about the river and its watershed.
Figure 1-4. The Los Angeles River Revitalization website contains artists’ renderings (A to C) of a rejuvenated river corridor.
Here’s where you pick up the thread in this book. You’ll use the city’s real need for river redevelopment as a launching point for a park siting analysis using a geographic information system (GIS). A GIS is ideal for this type of decision-making, because it allows you to analyze large amounts of data in a spatial context. In this book, you’ll spend a lot of time with ArcGIS Pro software, and by the end you’ll have completed a project from scratch. Along the way, you’ll gain an excellent grasp of what a GIS can do.
You’ll be assuming the role of a GIS analyst for the City of Los Angeles. So what exactly does a GIS analyst do, and how is that job different from other jobs that also use GIS