Working with GIS Data Lecture 1 of 2 Class 3 GISG 110

Objectives Working with Spatial Data Geographic data review Linking features and attributes Data formats Project and data management Working with ArcCatalog Metadata

Representing geographic features Vector (discrete) Raster Data components: –Geography (representation) –Attributes (characteristics) –Behavior rules (instructions) Point, Line, Polygon Rows + Columns Equally sized cells

Feature classes Feature class Groupings of features (points, lines, polygons) with the same type of geometry Can create point, line, or area feature classes Example 1: Highways, primary streets, and secondary streets = “Roads” (lines FC) Example 2: Seven territories that house identical wildlife species = “Habitat” (polygon FC)

Linking features and attributes Feature classes are tables that store spatial data Each feature has a record in the table

Spatial Data Formats ArcGIS can work with spatial data in multiple formats: –Raster –CAD –Shapefile –Coverage –Geodatabase –Internet Map Service (ArcIMS) –Tables

Shapefile Data Format Single feature class –Points or lines or polygons Attributes stored as dBASE (.dbf) table Consists of at least three files: –Shapefile name.shp –Shapefile name.shx –Shapefile name.dbf –Others may include.sbn and.sbx If coordinate system is defined, the spatial reference is also stored in shapefile: –Shapefile name.prj

Shapefile Display quickly Fully editable (coordinate and tabular in ArcGIS) Simple structure –Polygons do not share bounding lines

Coverage data format A folder containing multiple feature classes Can store point, line, polygon FC and more Attributes stored in a separate INFO table Commonly found format (due to ArcInfo market dominance) Data model more complex Display more slowly in ArcGIS Coordinate data not editable in ArcGIS Polymorphic (point/line/polygon/annotation)

Coverage Polygons share bounding lines Same topological rules can be built in geodatabase

ArcInfo Coverage organization Coverages must be stored in an ArcInfo workspace Workspaces contain an info folder The info folder stores information about the attribute tables Feature class Feature attribute table Point.PAT Point attribute table.PAT Point attribute table Arc.AAT Arc attribute table.AAT Arc attribute table Node*.NAT Node attribute table.NAT Node attribute table Polygon.PAT Polygon attribute table.PAT Polygon attribute table *Node – the beginning and ending points of an arc, topologically inked to all arcs that meet there

ArcInfo Coverage organization To manage coverages Only ArcGIS tools can be used Files in both the info and coverage folders are required Operating systems are unaware of this link (trying to view or copy coverage in Windows Explorer won’t work)

Geodatabase data format Stores spatial features and their attributes in the same RDMS –Different than SHP and COV (file-based) Geodatabases are sets of feature classes –World.mdb comprises a polygon FC for countries, a polyline FC of rivers, and a point FC of cities –Each geodatabase feature class only stores a single feature type Storage format: –Personal –Multiuser

Personal and multiuser gdb Personal Designed to store small to medium amounts of data (up to two gigabytes) Accessed by several users at the same time, but only edited by one person at a time Multiuser Suitable for large workgroups or enterprises Have no size limit Permit simultaneous editing by different users Work with RDMS (Informix, SQL Server, Oracle)

Geodatabase validation Validation Geographic features can be made to allow certain types of editing, display, or analysis, depending on circumstances the user defines Two types –Spatial validation (ArcEditor) Topology or Geometric Networks –Attribute validation Used with tabular data Required for maintaining data integrity and efficiency during management, display and editing

Geodatabase 1 st preferred vector format in ArcGIS Display very quickly Fully editable (coordinate and tabular) in ArcGIS Can store many files from many formats Store multiple feature classes Ability to store labels as annotation Create domains for attributes

CAD file data format Computer Aided Design files (DXF, DWG, DGN) Typically product of engineering software –E.g., utilities and infrastructure Logical collection –Access one or all feature class(es) at a time Coordinate data is not editable in ArcGIS –Edit after exporting to GDB FC, coverage, or shapefile Frequently contain “sloppy” data No enforced topology Gaps in data Frequently contain little or no useful attribute data

Converting tabular locations to a point FC Table with raw coordinates New point FC Table with addresses New point FC Add data to your map as…

Images and grids Rows and columns of equal-sized cells –Each cell stores a value –Detail depends on cell size Grids (ESRI native raster format) –VAT: report # of cells Images (TIFF, BMP, SID, JPG, ERDAS) Grids Images

Data Types (or Models) Two methods of representing geographic data: –Vector (points, lines, polygons) –Raster (images and grids)

Common Data Sources Local San Diego local governments National Global oad/freemaps.html oad/freemaps.htmlOther Yahoo or Google search: keywords “free GIS data”

Project and data management

GIS strengths and weaknesses Integrates large amounts of data in different formats from different sources Frequently creates data management nightmares Effective data management is absolutely essential

Common concerns Where are the source files? What types of files are they? What projection/coordinate system are they stored in? Are there multiple copies of the files? –If so, which are the most current or correct? Where are new files automatically placed? How do I move ArcMap documents between computers? These types of questions must be answered definitively for every project, regardless of the size of the project

General system file management GIS is more file-intensive than most applications Knowledge of operating system (OS) file system is critical Disk, directory, and file management skills –Disk space –Directory structure and nomenclature –File nomenclature, file sizes, multiple-file data sets Where (file system-wise) is every file in a current project?

Setting the working directory Before starting a new project Plan, plan, and plan some more Determine default location for new files Set working directory –Avoids major headache later –Have no doubts about where new files will be placed TIPS –Create a new directory for each project –Set working directory to the new directory

Renaming and copying Use caution when renaming and copying files Every file of a multiple-file data source (.shp,.shx,.dbf) must be renamed/copied Files that are renamed/copied will not be found in map documents Files (not layers) to be copied/renamed cannot be in use (being edited) in current project Data sources are frequently composed of multiple individual files –Shapefiles = at least 3 files –Image data = at least 1 file, at most 4

Renaming and copying Instead of Windows Explorer, use ArcCatalog to rename/copy and paste shapefiles

Renaming & Copying ArcCatalog functionality applies to any supported data sets Other files can be copied/moved/renamed using OS file management –Images –Text files –dBase files (not associated with shapefiles) –CAD files All supported vector data can be converted and managed as shapefiles or geodatabases

Archiving Why archive? Effectively manages your data Saves/stores large amounts of project data –No longer in use –Periodically in use Frees disk space Un-clutters directory structure

Archiving 3 ways to archive Create new and secure backup directories –Assuming your agency does not have own back up locations or archival systems Write stable media (CD, DVD, Zip) Use archiving tool, e.g., WinZip

Copying and moving ArcMap documents ArcGIS project files only contain pointers to data location File locations are “hard coded” into project files Copying and moving map documents (MXD) does NOT copy or move data sets

Copying and moving ArcMap documents Map documents can lose track of the source data –Source data gets moved (!) Use Source tab to change the data source for a layer –Shortcut: Right-click the layer > Data > Set Data Source Layers with misplaced data Click here to change the data source

Copying and moving ArcMap documents Data sets must be moved, copied, or specified Data structures must be completely recreated, or Map documents that are copied or moved must be altered for new file locations

Absolute vs. relative paths Absolute (full) paths C:\GIS\Project1\Boundary.shp Everyone who uses MXD must –Be on same computer OR –Have data on their computer in exactly the same folder structure Relative paths \Project1\Boundary.shp Specify the location of the data contained in MXD, relative to the current location of the MXD

Relative paths Enable the MXD and its associated data to be moved without the MXD having to be repaired (as long as same directory structure is used at new location) Allow users to share maps easily Data referenced by a relative path can be in the same folder as the MXD or in a folder above or below the MXD (recommend below) \Project1\finalproject.mxd \Project1\Boundary.shp or \Project1\Data\Boundary.shp

Exporting data Why export? To share data with others –ArcGIS users –Users of other software Integration with desktop publishing applications (e.g., MS Word) Archiving

Converting data to shapefiles Any supported vector data source can be converted to shapefile Polymorphic data sources need to be converted to several shapefiles –CAD files –ArcInfo coverages Shapefiles can be moved, copied, or archived easily and safely with OS (ArcCatalog recommended)

Exporting tables Tables can be exported to “generic” formats –dBase –ASCII tab-delimited –INFO Table subsets can be exported –Only selected records are exported Formats readable by other applications Use in spreadsheet or statistics software

Exporting tables How to export In ArcMap, open table and select Options From window, select Export and name new file (assumes same format)

Exporting maps File  Export Map Available in Data or Layout view Specify output type, location and name

Exporting maps Exported images can be imported to desktop publishing applications

ArcCatalog

Using ArcCatalog Database design & management –Manage data: Copy, Rename, Delete Provides a uniform view of all of your data Define or modify table and feature class definitions

Three ways to view data ArcCatalogContentsPreviewMetadata

The Contents tab ArcCatalog Large icons ListDetailsThumbprints –Data –Layers –Maps

The Preview tab ArcCatalog Geography or Table View –Choose from dropdown list –Build custom views

The Metadata tab ArcCatalog Create and display metadata in a variety of ways

Introducing Metadata What is metadata? –Descriptive information about data Metadata tabs –Description –Spatial –Attributes Create and edit Display using different formats: FGDC, ISO, XML

Connecting to folders ArcCatalog Connect to folders Connect to network Disconnect from folders

Setting viewable data ArcCatalog Tools  Options Turn all data types on or off

Creating thumbnail images Used by Contents thumbnail view 2.) Preview tab Choose object 1.) Choose object 3.) Zoom/Pan 4.) Create Thumbnail Icon

Review 1. ArcGIS can work with spatial data in multiple formats. (T/F) 2. Groupings of features (points, lines, polygons) with the same type of geometry are called ______. 3. A shapefile is a folder containing multiple feature classes. (T/F) 4. Attributes in the coverage format are stored in an INFO table. (T/F) 5. Both shapefile and coverage formats are composed of multiple files. (T/F) 6. It is best to manage your coverage data with your operating system. (T/F) 7. The _____ is the 1 st preferred vector format in ArcGIS. 8. What two types of validations are available for the geodatabase? 9. List two reasons to archive. 10. What is metadata? 11. What are the three ways to view data in ArcCatalog? 12. What keywords would you search on to find GIS data? 13. Absolute paths allow users to share maps easily by 13. Absolute paths allow users to share maps easily by moving your data without the MXD having to be repaired (as long as same directory structure is used at new location). (T/F)

Remainder of Class Break Lab Exercises: –ESRI Chapter 4 Exploring ArcCatalog –Exercise 1: Chapter 4 questions and SANDAG and Census Bureau data assignment (due 9/6/07)

Exercise Questions 4a 1. How many feature classes are contained in the world geodatabase (world.mdb)? 2. List the feature class of each: CitiesCountriesDisapp_areaWorld30 3. Using the ID tool, what is the population (POP_CNTRY) of: PeruIraqDenmark South Africa 4. What is metadata? 5. How many records are in the countries feature class? What is the Definition Source? Data type?

Exercise Questions 4b 1. Geographical searches use _____ and _____ coordinates to find data. 2. Sealfloor.tif is a _____ data set. 3. Why would sea floor elevation in East Oceania be useful in a map of where Earhart disappeared? 4. In seafloor.lyr, depth of water is indicated by the shade of _____; darker is _____. White areas are _____. 5. Layer files do not store symbology information. (T/F)

Exercise Questions 4c 1. How do you open ArcMap from ArcCatalog? 2. A map document can hae one or many data frames. (T/F) 3. Briefly describe the difference between the Data view and Layout view. 4. What are the two ways to add layers to ArcMap? 5. To change the name of a Data frame, you can simply left-click on the name and type the new name. (T/F)