Features, Formats & Attributes

1. Features, Formats & Attributes GIS 458 Spring 2006

2. Layer Types • Vector • Raster • Terrain and Other Surfaces • Other • Addresses • Geoprocessing Models • Survey Data • Networks

3. Vector Data • Discrete Data • Have precise shape and position • Best for defined shapes and boundaries • Have attributes and behavior • Points • Zero-Dimensional • Features too small to be lines or areas • Stored as single x,y coordinates

4. Vector Data • Lines • One-Dimensional • Features too narrow to be areas • Stored as series of ordered x,y coordinates • Segments: • Straight • Circular • Elliptical • Splined • Polygons • Two-Dimensional • Features that cover a broad geographic area • Stored as series of segments that enclose an area • Annotation • Descriptive labels • Associated with features • Display names and attributes

5. Raster Data • Gridded data composed of cells or pixels (picture elements) • Two-Dimensional • Values can depict various data • Light values (spectral) • Elevation (thematic) • Density (thematic) • Discrete or Continuous • Can also be stored in an attribute field • Photo of a building

6. Terrain & Other Surfaces • Triangulated Irregular Network (TIN) • Model of a surface • Stored as: • Integrated nodes • Triangles with edges • Enable surface analysis • Cannot be stored directly in geodatabase

7. Other Layer Types • Addresses • Data stored in database • “Locators” create features for locations • Geoprocessing Models • You create tools and store them • Survey Data • Data tables tied to feature coordinates • Networks • Require connectivity & topology

8. Attributes • Quality of an object • Size • Density • Name • Flow • Date • Population • A feature can have a number of attributes • Allow analysis & symbolization

10. GIS 458 Spring 2006 Instructor: Larry Clamp

11. Course Topics • Design Process • Layer Design & Formats • Raster vs. Vector • Point, Line or Polygon? • Relationships • Spatial • Non-Spatial • Attribute Table Design • Defining Appropriate Fields • Assigning Appropriate Field Types • Text, Integer, Double…

12. Course Topics, continued • Database Fundamentals • Purpose • Personal vs. Enterprise • Database Design • Database Implementation

13. Course Topics, continued • Software Selection • Database software (Oracle, SQL, etc.) • GIS Software…is ESRI the best? • Data Standards • FGDC • Personnel • Project Management • Data Mining

14. BREAK!!!!

15. GIS (Geographic Information System) • Consists of: • Computer hardware • Software • Geographic data • Personnel • Is a computer system that stores and links geographically-referenced information with graphic map features to allow a wide range of: • Information processing and retrieval • Display operations • Map production • Analysis, and • Modeling

16. Benefits of a GIS (Functionality) • Data entry/updating: access the database to update, add or delete information • Data conversion: take diverse information, formats, etc. and make them compatible • Data retrieval: take massive amounts of stored information and access it • Data manipulation: select via query and classify (symbolize) in different manners • Data presentation: present retrieved information in either text, tabular or map format. • Spatial analysis: take spatial data and make queries (from simple to complex) and generate new data from the original set

17. Three general operations in a GIS: • 1. Attribute queries (aspatial queries): • How many parcels in an attribute table are zoned R-7 and what is their total acreage? • 2. Spatial queries: • How many pulp plants are located within 500 meters of a river? • 3. Generation of new data sets from the original database: • Out of a marine mammal dataset, where are just the Beluga whales located? • Are there areas where ring seals and orcas overlap?

18. What is “Spatial Data”? • Spatial means it is “mappable”, that is, every piece of information is attached to a specific object on the map and that object’s location on the map is geographically-referenced • Reference systems typically use latitude/longitude, UTM, SPC or some type of x,y coordinate system

19. Where do we get “Spatial Data”? • From a variety of sources: • U.S. census • Land use surveys • Satellite imagery • Aerial photographs • Paper maps • Problem: compatibility • Projections/coordinate systems--Albers Equal-Area Conic vs. UTM • Map scale--1:2,000 vs. 1:2,000,000 • Data formats--DRG, (raster), Shapefile (vector)

20. Examples of GIS Data Structures

21. Organizing Geographic Data GIS 458 Spring 2006 Larry Clamp

22. Parts of the Whole • Geodatabase • Geographic Datasets • Object Classes • Feature Classes • Topological Classes • Relationship Classes

23. Geodatabase • A collection of data types • Datasets & feature, object and relationship classes • Can span one, several, or many geodatabases • Manage seamless geographic data • Two main types • Personal • Represent small to medium-sized datasets • Enterprise • Represent large or complex datasets (multiple users)

24. Geographic Datasets • Feature Dataset • Collection of feature classes • Common coordinate system • FC’s must be in FD’s for topology • Raster Dataset • Simple (basic GRID) • Compound (multiple bands, etc.) • Triangulated (TIN) Dataset

25. Object Classes • Table that can associate behavior • Descriptive information about objects • Owners • Stream Codes • Annotation

26. Feature Classes • Collection of features with same geometry • Points, lines, polygons • Simple feature classes • No topology • Features are independent of one another • Topological feature classes • Features are bound to one another • Share certain behavior

27. Relationships

28. Relationships

29. No…Seriously • Relationship class • Table that stores realtionships between features or objects • Models dependencies between objects • Can control what happens to related objects • Removed • Changed

30. Keep it Simple… • Geodatabase = Filing Cabinet • Feature Dataset = Filing Cabinet Drawer • Feature Class = Individual Folder in Drawer

31. Sub-Types & Attribute Domains GIS 458 Spring 2006 Larry Clamp

32. Sub-Types • Objects (rows) in a table or feature class grouped by an attribute • Roads by class: Highways, major roads, arterials, etc. • Allow users to make validation rules more specific to data • Help insure data quality • Speed up data entry and editing • Help eliminate need for additional classes • Wells: Different class for public, agricultural or monitoring wells or • Just different sub-types?

33. Sub-Types, continued • Based on integer attribute field • Integer codes and descriptions entered • Editor constrained to entered values • In ArcMap, description is displayed • Description used for labeling

34. Setting Sub-Types • Set as properties of an existing table or feature class • Go to Properties dialog • Select integer sub-type field • Input code and description • Can also set defaults and domains

35. Attribute Domains • Define legal field values for tables, feature classes, or sub-types • Defined as properties of the geodatabase • Can be shared across the geodatabase • Assigned to fields by editing field properties of tables & feature classes • Do not constrain incorrect data entry but will find errors • Validation tool on Editor menu

36. Legal Values • Two Types of domains • Range and Coded Values • Type used depends on nature of attribute data

37. Range vs. Coded Values • Range domains • Apply to values for numeric attributes • Used for measured data • Well depth • Contamination levels • Power pole heights • Legal minimum and maximum

38. Range vs. Coded Values • Coded values • Apply to any type of attribute • Text, numeric, date, etc. • Used for coded data • Land-use codes • Water pipe material codes • Street surfacing codes • Define list of legal codes and their descriptions

39. Splitting & Merging Features • Domains allow you to define how attributes are handled during splitting & merging • Split policy • Merge policy

40. Split Policies • Defines what values are assigned to resulting features • Default value • Each take on a default value you set • Duplicate value • Each take on a copy of original value • Geometry ratio • Each take on a ratio of the original value

41. Merge Policies • Dictates what happens to values of merged features • Default value • Each take on a default value you set • Only policy that applies to nonnumeric fields and coded value domains • Sum • Sum of the original features • Geometry weighted • Weighted average of original features

42. Summary

43. Table Design & Importing Data GIS 458 Spring 2006 Larry Clamp

44. Ways to create tables • ArcCatalog • Right click location • Folder, geodatabase… • Select New>Table to access wizard • You can import fields from other tables • Geoprocessing (ArcToolbox) • Under Data Management Tools • Select Table toolset > Create Table

45. Table Field Properties • Alias • Allow NULL Values • Default Value • Domain • OBJECTID • Length • Precision • Scale • BLOB • Raster

46. Alias • Alternate field name for display in ArcMap • Less cryptic… • Can be changed after the table is created

47. Allow NULL Values • Indicates field may or may not contain null data • Null value = absence of recorded value • Different than 0 (which is a value) • May NOT be changed after table is created

48. Default Value • Value that is automatically assigned for a new record • May be changed after table is created

49. Domain • Assigned geodatabase domain for field • Defines legal values • Can also define how feature attributes are handled if they are merged or split • May be changed after table is created

50. OBJECTID • Automatically generated • DO NOT delete or change it in any way!!