target="_blank" rel="nofollow" href="#ulink_6073a776-7909-5758-8e20-21f9ef97b15b">Exercise 1-1
Review
Over the last 30 years, the way that geographic features have been portrayed, stored, and manipulated in geographic information systems (GIS) has evolved from a file-based technology into the present-day Esri geodatabase format. By using the Esri geodatabase, GIS practitioners can more realistically manage geographic features and their relationships to other features. Although computer technology has enhanced the behavioral aspects of these relationships, the fundamental ways that these geographic features are represented—by points, lines, and polygons—has largely remained unchanged. Esri geodatabase technology has improved the management of these points, lines, and polygons by providing tools to create geographic feature representations, enforce data integrity, and establish relationships among the geographic features that more closely model real-world situations.
As illustrated in the previous exercise, the opportunities to manage data using GIS methodology can be enhanced by careful thought and preplanning to ensure that an accurate portrayal of geographic features and their relationships is contained in the geodatabase. Preplanning the geodatabase is enhanced through a structured, organized logical data model to ensure that every conceivable relationship is accounted for in the model. This preplanning phase is no easy task. However, it is much easier to spend time at the outset designing your geodatabase than it is to change it once you’ve begun entering data into the model.
Organizing your geodatabase using feature classes and feature datasets allows you to refine relationships and behaviors for the data. Feature classes, as the most basic representation of geographic data in the geodatabase, can be logically grouped together to form feature datasets. Although there are many different techniques for organizing geographic data in the geodatabase, the organization of the data must be guided by the behavior of these features in the real world. For example, if feature classes contained in the geodatabase work together to form a geometric network, represent a terrain, or establish a topology, the feature classes must reside in the same feature dataset. Such behaviors among the data must be considered while designing the geodatabase.
Once your design is complete, using domains for your attribute data and other techniques will reduce costly mistakes during the data entry phase of your geodatabase’s development. Additional techniques provided by the geodatabase, such as the creation of subtypes, optimize how data is organized and utilized within the geodatabase. Using the many tools available within your project, and with a thoroughly planned approach, your new geodatabase will adequately portray the geographic features and associated relationships among them. As a result, your model of reality as contained in the geodatabase will represent the real-world features as closely as possible.
STUDY QUESTIONS
Answers to the study questions in this book are available on the instructor resources DVD.
1.What is a logical model of a geodatabase, and why should you develop a logical data model when designing your geodatabase?
2.What are the principal advantages of using subtypes? Give one example of a situation in which you would create a subtype, and specify why.
3.What are the principal advantages of using domains?
4.What is the difference between feature classes and feature datasets? When must you create a feature dataset?
Other study topics
Search for these key phrases in ArcGIS Pro Help for further reading:
1.Fundamentals of the geodatabase
2.What is a geodatabase?
3.Introduction to attribute domains
4.Fields, domains, and subtypes
Tutorial 1-2: Creating a geodatabase–expanding the logical model
The components of a geodatabase can have various spatial relationships, or behaviors, that form a topology. These behaviors can exist among points, lines, and polygons and will impact the logical model of a database. The most efficient designs will consider topology from the beginning.
LEARNING OBJECTIVES
•Design linear feature classes
•Investigate data behavior
•Design for topology
•Design point feature classes
Introduction
The first tutorial used the geodatabase design forms to construct a logical design for a parcels database. That dataset consisted of a polygon feature class along with a linear feature class to aid in symbolizing the parcel boundaries.
In this tutorial, you will design another set of feature classes to store data for a sewer system. The process will include investigating the behavior of the data, and then trying to accommodate it in the design.
Remember to look at how the data will interact with feature classes, as well as any possible domains or subtypes that may be used. This investigation will help to build not only an efficient design but also a good model of reality.
Designing the data structure
Scenario
After your successes with the parcels and zoning datasets, Oleander’s Public Works Department is seeking your help to create a geodatabase for the sewer system. You will need to design this geodatabase for them.
Sewer systems are a simple design. They consist of pipes to carry wastewater to the treatment plant. In real life, it’s important that the pipes connect to ensure a direct flow route from the beginning of the system to the end. In the data model, you will also want to ensure connectivity, which will allow the data to be used later to construct a network dataset.
A great amount of data can also be stored as attributes of the linear features. Some of the basic information includes the size of the pipe, the material it’s made of, and the year of installation.
This portion of the process is intended to inspire thought and creativity. If done correctly, your designs will be viable for years to come. Once all the designs are completed, they will be used to create the data structure in ArcGIS Pro.
Data
Since you are creating this geodatabase from scratch, there is no data to start with. But you will need to print the geodatabase design forms from the downloaded materials as an aid in the design process. Print as many of the pages as necessary to contain all your designs.
Tools used
•Geodatabase design forms
Begin the geodatabase design process
Using the geodatabase design forms, you will once again commit your thoughts to paper and examine all aspects of how the data will be used, edited, and symbolized. The first part of the design will be to name the geodatabase. Since the data likely will be used in a network later, it will also require a feature dataset.
1.On the first page of a new set of design forms, write the name of the new geodatabase as Utility_Data. On the next line, add the name of the feature dataset as Wastewater.
The sewer lines will be built as linear features, which will require a feature class.
