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Features, Formats & Attributes

Features, Formats & Attributes. GIS 458 Spring 2006. Layer Types. Vector Raster Terrain and Other Surfaces Other Addresses Geoprocessing Models Survey Data Networks. Vector Data. Discrete Data Have precise shape and position Best for defined shapes and boundaries

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Features, Formats & Attributes

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  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

  9. GIS 458 Spring 2006 Instructor: Larry Clamp

  10. 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…

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

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

  13. BREAK!!!!

  14. 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

  15. 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

  16. 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?

  17. 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

  18. 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)

  19. Examples of GIS Data Structures

  20. Organizing Geographic Data GIS 458 Spring 2006 Larry Clamp

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

  22. 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)

  23. 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

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

  25. 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

  26. Relationships

  27. Relationships

  28. 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

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

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

  31. 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?

  32. 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

  33. 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

  34. 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

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

  36. 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

  37. 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

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

  39. 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

  40. 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

  41. Summary

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

  43. 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

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

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

  46. 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

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

  48. 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

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

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