Working with GIS Data Lecture 1 of 2

1. Working with GIS DataLecture 1 of 2 Class 3 GISG 110

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

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

4. 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)

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

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

7. 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

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

9. 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)

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

11. 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 *Node – the beginning and ending points of an arc, topologically inked to all arcs that meet there

12. 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)

13. 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

14. 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)

15. 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

16. Geodatabase • 1st 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

17. 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

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

19. 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

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

21. Local www.sandag.org www.sangis.org San Diego local governments National www.census.gov www.usgs.gov www.nationalatlas.gov Global www.geographynetwork.com http://www.manifold.net/download/freemaps.html Other www.gisdata.blogspot.com Yahoo or Google search: keywords “free GIS data” Common Data Sources

22. Project and data management

23. 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

24. 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

25. 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?

26. 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

27. 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

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

29. 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

30. 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

31. 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

32. 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

33. 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 Click here to change the data source Layers with misplaced data

34. 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

35. 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

36. 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

37. 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

38. 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)

39. 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

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

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

42. Exporting maps • Exported images can be imported to desktop publishing applications

43. ArcCatalog

44. 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

45. Three ways to view data ArcCatalog • Contents • Preview • Metadata

46. The Contents tab ArcCatalog • Large icons • List • Details • Thumbprints • Data • Layers • Maps

47. The Preview tab ArcCatalog • Geography or Table View • Choose from dropdown list • Build custom views

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

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

50. Connecting to folders ArcCatalog • Connect to folders • Connect to network • Disconnect from folders