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Tutorial:
Section 1
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| Getting
Started ArcGIS Applications Description:
Data Retrieval: Data collection and preparation is one of the most expensive and time-consuming aspects of creating a GIS facility. There are many governmental and commercial data sources that provide digital and tabular data sets as well as analogue data including maps, aerial photographs, and satellite imagery. ArcGIS Supported Data Formats: ArcGIS allows the user to work with an extensive array of data sources. These are listed below.
About Data Sources: A data source is any geographic data that may be used as input to or output from a geoprocessing tool. Supported data sources include:
When working with data it is helpful to understand how ArcGIS organizes the data sources with which the program's tools work. Data sources are organized into folder hierarchies on your computer. ArcGIS generally recognizes three different workspaces:
- with the option set more. When you open ArcCatalog you will likely see one or more of the following workspaces in the catalog tree with various data sources contained within them.
About Workspaces
Folders may contain other folders, geodatabases, data sources (e.g., rasters, shapefiles, tables, etc.), and toolboxes. Some data sources (coverages, shapefiles, TIN datasets, layers, and layer files) can only live inside folders. Other data sources (raster data, feature classes, and tables, and more) can be exported from a folder to a geodatabase - either personal or ArcSDE. Feature datasets within a folder (coverages, Smart Data Compression [SDC], Vector Product Format [VPF] and more) can be set as workspaces. Geodatabases There are two types of geodatabases in ArcGIS:
Geodatabases contain geographic information organized in the form of feature classes, feature datasets, tables, and toolboxes. Feature classes can be organized into feature datasets or may exist independently in geodatabases.
Personal geodatabases can be created in which to store and manage your own spatial database. Microsoft Access is the database used. With personal geodtabases many users may read the database simultaneously but only one user may edit.
With ArcSDE geodatabases many simultaineous editors are supported.
About Data Sources Geographic data used as input to or output from a geoprocessing tool is considered a data source. The list of supported data sources includes:
The feature class is one of the most commonly used data sources. A feature class is composed of a collection of geographic features with identical type of geometry (point, line, polygon) and the same set of attributes. Feature classes can be found within a geodatabase feature, shapefile, coverage, CAD, SDC, and VPF, as well as within a geodatabase. Feature data
Geodatabase feature datasets live inside personal or ArcSDE geodatabases. Feature datasets contain feature classes that are of the same extent and coordinate system.
Geodatabase feature classes are stores of geographic features represented as points, lines, polygons, annotations, dimensions, attributes, and more. Feature classes that store topological features are contained within a feature dataset to ensure a common coordinate system. Other feature classes that are outside a feature dataset are called standalone feature classes.
A shapefile dataset (.shp) is stored in a folder, is composed of geographic features and their attributes, and contains a single feature class. Points, lines, or polygons (areas) represent geographic features in a shapefile.
An integrated set of feature classes that represent geographic features is called a coverage and is stored in a folder on your file system as a workspace.
A set of either points, lines (arcs), polygons (areas), routes, tics, links, and annotation (text) that have topology (defined relationships between features) between features that are within or between feature classes.
The ArcGIS feature representation of a CAD file. CAD feature datasets can contain one to five read-only feature classes: points, polylines, polygons, multipatches, and annotation.
Read-only members of a CAD feature dataset.
A Smart Data Compression dataset contains read-only feature classes, all of which have the same attribute informaiton but with different levels of generality in the shapes. SDC data is encrypted and compressed. ESRI uses the format to provide StreetMap™ data. Commercial data vendors distributing street data for geocoding and routing with various ESRI® software products also use SDC.
Store a set of points, lines, and polygons that may or may not have topology determining relationships between features that are within or between feature classes. SDC feature classes support a licensing mechanism that is used to bind access to a specific ArcGIS application, such as ArcReader™, or to a specific extension, such as ArcGIS Business Analyst.
These are a U.S. Department of Defense military standard that defines a standard format, structure, and organization for large geographic databases. VPF datasets contain feature classes that are read-only.
VPF feature classes are a collection of features that have the same attributes. Each feature class contains point, line, polygon, or annotation features,a nd has an associated feature attribute table. This type of feature class is read-only.
Raster data
A collection of one or more bands of a supported raster type such as TIFF, ESRI GRID or MrSID. Raster datasets can live in a folder in a file system.
A bands is a matrix of square cells that describes the characteristics of an area and their relative positions in space. Each cell contains a value indicating what it represents.
Raster catalogs are a collection of raster datasets organized in a table. Table records define the individual raster datasets included in the catalog. There are times when it is necessary or desirable to display adjacent or overlapping raster datasets without having to mosaic them into a large file. Raster catalogs are designed to avoid the need to mosaic.
TIN data
These are datasets often used to display and analyze surfaces. TIN datasets contain irregularly spaced points that have x, y coordinates describing their location and a z-value that describes the surface at that particular point. TINs can be used to represent elevation, precipitation, temperature, and more.
Layer data Layer data is temporarily stored in memory; it is not stored on saved on disk. As such, it only remains available within the current session. Layers created in ArcCatalog cannot be used in ArcMap and layers created in ArcMap cannot be used in ArcCatalog. One of the principal purposes of layers is to allow for attribute or locational selections without affecting the original data source.
Layer files (.lyr) are files that contain multiple references to geographic data stored on your disk. When layer files are opened multiple geograhic files are accessed. Most of the data sources supported in ArcCatalog can be referenced. Layer files are used to present a cartographic view of your geographic data.
These are files created by the ArcGIS Geostatistical Analyst Extension.
Table data
Tables contain data elements arranged in rows and columns. Each row represents an individual entity, record, or feature, and each column represents a single field or attribute value. Tables can contain attributes that can be joined to datasets to provide readily accessible additional information about geographic data.
Viewing Data in ArcCatalog: Once the user has successfully acquired GIS data in one of the aforementioned supported formats, it can be previewed using the ArcCatalog application. Note: If the data format is listed under the above heading "ArcGIS Supported Data Types," it can be simply viewed without the need to actually import using an import utility. If the data format is listed under any of the other headings (above), the data will first need to be imported. This can be done using ArcToolbox. The basics of using ArcToolbox will be described later. The ArcCatalog application window includes the catalog display that allows you to preview data, either spatially or tabularly, a catalog tree for browsing the data, and several toolbars.
The data can be previewed by navigating to its location in the catalog tree. If the folder or network drive that contains the user's data is not shown in the existing catalog tree, the Connect to Folder button can be used. Once the GIS data is listed in the catalog tree, navigate to it using the plus sign ("+") next to the data folders and simply click on the data layer. Select the Preview tab at the top of the catalog display. The layer will now be visible in the catalog display section of ArcCatalog. The geography toolbar can be used to zoom in and out, pan around the image, view the full extent of the data layer, identify attributes contained within the features of the data layer, and create a thumbnail view of the image.
As well as previewing the geography of a data set, the user can also preview the attributes. At the bottom of the catalog display, there is a preview drop-down list. This allows the user to view either the geography or the associated attribute table for the data layer.
Once the attribute table is visible, the user can scroll through the table to see the attributes contained within the the data layer. In addition to previewing the geography and the attribute table of a data layer, the user can view or create metadata. By clicking on the Metadata tab in the catalog display, technical information about the data set (such as its coordinate system, its spatial extent, description of its attributes, and descriptive information about when and how the data was created) can be obtained. The technical metadata is maintained automatically by ArcCatalog. However, the descriptive information must be updated by the users who manipulate and manage the data. Though ArcCatalog does not require the user to maintain this information, it is important for the GIS user to do this. For more information on how to manage metadata click the Contents tab in the ArcGIS Desktop Help and navigate to ArcCatalog/Working with Metadata. Viewing Data in ArcMap: The ArcMap application window consists of a map display for viewing spatial data, a table of contents for listing the layers shown in the display and a variety of toolbars for working with data.
When ArcMap opens, the ArcMap dialog appears on top of the application window. To open a data layer, the user can specify, whether or not they want to start using ArcMap with a new empty map, a template, or an existing map.
There are two ways to add data layers to the map display: 1. Go to File / Add Data... on the main menu toolbar OR click on the Add Data button on the standard toolbar.
Navigate to the data layer of interest. Select it, and click the Add button.
2. Simply click the name of the data layer from the ArcCatalog data tree, and drag it anywhere within the ArcMap display.
The user can add multiple data layers to the ArcMap Display, regardless of whether or not all data layers are spatially alike (have the same projection and datum). ArcGIS transforms layers of different projection and datum "on the fly" to the ArcMap Display. These layers can be temporarily made visible or invisible by clicking on the check box located next to each layer name in the ArcMap table of contents. When multiple data layers are visible, the user can drag a layer to the top of the table of contents in order to place that data layer on top of all of the other layers. In the following example the Interstate Highway layer was moved to the top of the table of contents in order to make data visible within the map display window.
In the table of contents, the user can right click on the name of a data layer. A context menu opens, which allows the user to begin a variety of operations.
The ArcMap Tools toolbar can be used to do a variety of operations. The toolbar may initially be oriented vertically, but its orientation can be changed by dragging one of its corners. Additionally, it can be moved so that its location is next to the standard toolbar.
A user can zoom into a region of interest within their data layer, and save that zoomed location. This allows the user to easily navigate back to that region of interest. This can be done by going to the View Menu, pointing to Bookmarks, and clicking Create.
A dialog box appears that allows the user to name the spatial bookmark.
After a spatial bookmark has been saved, the user can click the View menu, point to bookmarks, and the name will appear in the bookmark list. If the user selects the bookmarks, the map display will automatically zoom to that location. In a GIS, a feature on a map may be associated with a great deal of information. This information is stored in an attribute table. A layer's attribute table contains a row (or record) for every feature in the layer and a column (or field) for every attribute or category of information. To open the attribute table for a data layer in ArcMap, right click on the layer in the table of contents. Select open attribute table.
Below is an example of an attribute table for United States GIS data layer. The FID field contains a unique identification number for every record (or every feature within the map). The intersection of a record and a field is a cell. A cell contains an attribute value. For example, the attribute value of the STATE_NAME field for the first record is "Hawaii."
Records, as well as fields, can be highlighted. When a record is highlighted in a table, its corresponding feature is highlighted on a map. A highlighted record or feature is said to be selected. The user can highlight a record in a table by clicking on the left edge of the record of interest in the table. Once the record is selected, the corresponding feature will be selected in the map display.
The user can clear selections by clicking on the options menu at the bottom of the attribute table and selecting the clear selection option. The record becomes unselected in the table and in the map display.
Various statistics can also be computed for a particular attribute field. To perform this operation the user should right click on the field of interest, and select statistics.
A dialog box appears with the statistics for that selected field. The statistics box displays the number of records in the table and the minimum, maximum, sum, mean, and standard deviation values. The frequency distribution chart represents the distribution of values graphically. The following shows area statistics using all records in the attribute table.
Using ArcToolbox: ArcToolbox is the application that provides an environment for performing geographic information system (GIS) analysis. ArcToolbox allows the user to perform a variety of geoprocessing tasks including data conversion. Geoprocessing tools are organized into toolboxes and toolsets within ArcToolbox. The toolbox is organized into toolsets that provide solutions for different types of tasks. The eleven toolsets may be seen listed in the graphic immediately below. Four of the more frequently used are briefly described.
The user can access ArcToolbox through either ArcCatalog or ArcMap via the ArcToolbox (red toolbox) icon on the standard toolbar. In the graphic below two shapefiles (intrstat.shp and states.shp) have been added to ArcMap. From ArcMap ArcToolbox was called up, the Conversion Tools toolbox opened, and the Export to CAD tool selected to convert the intrstat.shp file's features to the DWG_R2004 format. In both ArcMap and ArcCatalog the user may either navigate to the data to be used within a particular tool, or the data layer can be drag and dropped from the table of contents or catalog tree respectively, into the dialog box of the toolbox of interest. To perform this operation the ArcToolbox icon should can be selected. In the Toolbox, a tool of interest can be double-clicked to start. The user can then click and drag on the dataset (in the table of contents or catalog tree) and drop in the "add data" box of the tool.
End of Section 1. Go to: Last modified: Friday, August 12, 2005 |
Folders
Personal
geodatabases
ArcSDE geodatabases
Geodatabase feature datasets
Geodatabase feature classes
Shapefile
datasets
Coverage
datasets
Coverage feature class
CAD feature datasets
CAD
feature classes
SDC
datasets
SDC feature classes
VPF datasets
VPF feature classes
Raster
datasets
Raster dataset bands
Raster catalogs
TIN datasets
Layer files
Geostatistical layer files
Tables
