GIS 1 - Lab 1: Getting Started with a Geodatabase in ArcGIS

Goal/Background

The objectives of the course were for users to be able to describe components of the geodatabase, create a geodatabase schema, and design and create a geodatabase.

Important Components of a Geodatabase

Geodatabases can comprise of a multitude of components such as feature classes, feature datasets, tables, and mosaic datasets. Geodatabases are used to store, query, and manipulate spatial data. This function is very useful when making a map that depends on trends and can mimic real-world scenarios. 

Feature class: a collection of geographic features with the same geometry type, attributes and spatial reference. 

        -Geometry types can be either a point, line, or polygon

Feature dataset: Stores spatially related feature classes in a common dataset for building topologies, network datasets.

        -needs to have the spatial reference specified prior to adding feature classes to dataset

        -must have the same coordinate system/spatial reference

        -features must share common geographic area

        -can have varying geometry types

Non-spatial table: stores data without spatial qualities to provide extra information to spatial data included in map.

        -attributes populate the table

        -attributes are linked to a feature by a unique identifier

Mosaic dataset: a collection of raster datasets or images that can be viewed as one seamless image. (similar to pasting maps with same scale and location next to one another to view it as a larger image) The images are stored as a catalog of mosaicked images.

        -footprint is the extent that each raster dataset in the mosaic dataset/image reaches (often rectangular images/selections)

        -footprint is not necessarily the extent of a particular image, but rather the entirety of the raster.

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Methods

Exercise 1: Explore a Geodatabase 

Exercise 1 is meant to help the user to play around with the features, components, and structures as described in the introductory and sample videos. This includes how to download the data required for the projects involved, how to set up a folder connection, identify types of feature classes, datasets, and geodatabases. Focus is brought to examining the feature datasets and identifying coordinate systems for different types of features within the geodatabase. Feature classes are also highlighted in order to help the user recognize differences between geometric properties within the attribute table and properties pop-ups. Finally, the user has enough of a background to create their own feature class to add to the predetermined geodatabase. 

Exercise 2: Explore a Mosaic Dataset 

Adding to the previous exercise, this exercise is made to introduces the user to mosaic datasets and raster images. This exercise uses the AlachuaCounty file geodatabase to show a feature dataset, mosaic dataset, and a stand-alone feature class within. This map uses four images to show a specific area in Florida. Their footprints are the lines of where each image reaches their edge, and where it may overlap with another. The exercise demonstrates how to go about understanding and navigating through a collection of rasters that make up a mosaic dataset. 

Exercise 3: Create a Geodatabase and Add Initial Data

Exercise 3 has the user import existing data from San Diego, California into a new geodatabase. The purpose of the exercise is to get the user to explore spatial and attribute data stored in coverages and shapefiles in a map format. Emphasis is placed on the different ways in which one can import data to the dataset or geodatabase. Importing as a feature class (single), a shapefile, a CAD dataset, or importing as multiple files are introduced within this exercise. Also introduced is the tool for excluding extraneous information from the selected imported fields. 

Exercise 4: Add Remaining Data to the Geodatabase

By adding more data to the geodatabase created in exercise 3, a more complete geodatabase is formed in an organized fashion by controlling the structure, or schema. Loading the schools feature class and making it inclusive to higher and lower education gives way to a new feature class called AllSchools. By adding a new coordinate system that all subsequent information will also contain, one can create a functional and organized dataset. The addition of a table provides context for the data included on the map that is being made. 

Exercise 5: Create a Mosaic Dataset (Standard or Advanced)

Exercise 5 uses skills learned in the past 4 exercises and puts them all to use by creating a new mosaic dataset from the provided aerial images. The new mosaic dataset being made in this exercise uses aerials imagery to contain the boundary, footprint, and image layers. The images need to be compressed at a certain setting in order to make sense in the map. Rasters are added to the dataset to provide the imagery associated with the seamless image. Colors can be changed in aerial pictures to utilize different functions in the program. 

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Result

Final geodatabase structure.

Geodatabases have a vast array of important features and uses. Whether it be a tool for city planners to use in order to plan a new bike path, or even where to avoid going during the zombie apocalypse, the applications of these features are up to the imagination and skill of the user! In this particular course, this completed geodatabase could be useful for expansion or maintenance of the county of Alachua, Florida. 

Source of the course and relevant information

Balstrom, T., Dr. (n.d.). Find Areas at Risk of Flooding in a Cloudburst. Retrieved November 06, 2017, from https://learn.arcgis.com/en/projects/find-areas-at-risk-of-flooding-in-a-cloudburst/