ArcINFO Workstation Basics ArcINFO subsystems feature classes the

Arc/INFO Workstation Basics Arc/INFO subsystems; feature classes; the coverage; file structure; topology; feature attribute tables; data storage for points, lines and polygons 1 – UT Dallas POEC 6382 Applied GIS Software

What is Arc/INFO? • A very sophisticated and voluminous set of tools and commands for spatial data input, management, and analysis. • Contains an internal database management system (INFO), but can be connected to external standard data base environments via SDE (Spatial Database Engine) • Under UNIX, is command driven (over 2000 commands), with GUI/application development capability via AML (Arc Macro Language) • Under NT, new (Jan 2000) GUI-based product Arc. Info Desktop (Arc. Catalog, Arc. Map, Arc. Toolbox) complements the classic command environment which is still available as Arc. Info Workstation 2 – UT Dallas POEC 6382 Applied GIS Software

Arc/INFO workstation subsystems Core subsystems: – ARC - Arc is the overall GIS manager; it is not a graphic module. Use Arc to: • Generate and manage coverages in the database • Convert data from other digital formats • Perform spatial analysis in one or more coverages – ARCPLOT - Arcplot is a graphical module for map display and query. Use Arcplot to: • Display spatial and attribute data for one or more coverages • Query spatial and attribute characteristics • Create layouts and maps, and generate plot files – ARCEDIT - Arcedit is an interactive graphics editor. Use Arcedit to: • Digitize and edit one coverage at a time • Correct errors in spatial and attribute data – INFO - INFO is the relational data base management system (RDBMS). 3 – UT Dallas POEC 6382 Applied GIS Software

Arc/INFO Workstation Subsystems, cont’d. • ARC Macro Language (AML) - A high-level, algorithmic language that provides full programming capabilities and a set of tools for building menus to tailor user interfaces for specific applications. It has an independent processor and allows you to: – Use AML directives and AML functions in any subsystem, interactively or in programs. – Build programs that incorporate Arc/INFO commands – Create on-screen menus • Being replaced by Visual Basic for Applications – More flexible – Information industry standard rather than GIS specialty – But generally more complex to learn and use 4 – UT Dallas POEC 6382 Applied GIS Software

Arc/INFO Subsystems, cont’d. Other Subsystems: – Tables - Tables is a tabular management system that uses INFO files to create, store, edit, and query tabular data – Librarian - Librarian is a separate set of software tools to manage and access large geographical data sets in map libraries. A map library is a collection of spatial tiles used to spatially partition large data layers. Librarian commands create and define a map library, move data in and out of a library, query the data in a map library, and display the results of a query. Librarian requires exact attribute consistency. – Arc. Tools - Arc. Tools consists of 5 AML-based productivity tools, implemented through a graphical user interface (GUI), for common Arc/INFO operations and functions. • Crude predecessor to Arc. Map GUI, but now obsolete • Do not confuse with Arc. Toolbox—very different 5 – UT Dallas POEC 6382 Applied GIS Software

Extensions: Arc/INFO Subsystems, cont’d. – GRID - Grid provides a fully-integrated raster (cell-based) geoprocessing system for use with Arc/INFO. GRID supports a Map Algebra spatial language that allows sophisticated spatial modeling and analysis. Example of use: resampling – NETWORK - Network performs address matching/geocoding, allocation, routing, and pathfinding across linear networks. – TIN - software used for surface representation, modeling and display. A TIN (Triangulated Irregular Network) is a set of adjacent, non-overlapping triangles computed from irregularly spaced points with x, y coordinates and z values. The TIN model stores the topological relationship between triangles and their adjacent neighbors which allows for the efficient generation of surface models for the analysis and display of terrain and other types of surfaces. – COGO - Abbreviation of the term COordinate Ge. Ometry. Used by land surveyors and others who require accurate coordinate geometry to capture and edit survey data, to calculate precise locations and boundaries, and to define curves. – Arc. Scan - Scan digitizing for raster to vector conversion – Arc. Storm - Data storage facility and transaction manager for feature-oriented georelational database management. 6 – UT Dallas POEC 6382 Applied GIS Software

Geographic Data • Two components of geographic data – Spatial Data: representations of geographic features associated with real-world locations • Feature classes: – points/nodes – lines/arcs – areas/polygons (single x, y locations) (linear string of x, y locations) (closed string of x, y locations) • Stored in files and managed by the GIS software (e. g. can be displayed in Arc. Plot, edited in Arc. Edit) – Attribute Data: descriptive information • stored in tables and managed by an RDBMS (Info or Tables) 7 – UT Dallas POEC 6382 Applied GIS Software

The coverage • Basic unit of storage in Arc/Info. • Digital version of a single map sheet layer and generally contains one type of map feature such as streets, parcels, soils, or vegetation. • Contains both the coordinate/spatial data and the descriptive data for features in a given geographic area. • * Stored as a directory (folder) which contains related files describing the location and attributes of the features, with additional files in the INFO directory at the same level. • An identifier, a unique number for each feature in the coverage, is stored in both a coordinate file (internal) and the attribute file. This ensures a strict one-to-one correspondence between spatial and attribute data. 8 – UT Dallas POEC 6382 Applied GIS Software

Anatomy of a Coverage 9 – UT Dallas POEC 6382 Applied GIS Software

File Structure, page 1 • Arc. Info coverages consist of a series of files in two folders, both at the same directory level (called a “workspace”). • The INFO folder contains the feature attribute tables and related tables for all coverage in that workspace. Unfortunately, the files are not identifiable by their names 10 – UT Dallas POEC 6382 Applied GIS Software

File Structure, page 2 Compare to Arc. View File Structue • Arc. View Shapefiles consist of three primary files, e. g. » road. shp » road. shx » road. dbf • Files can be dragged, dropped, cut and pasted into other folders without damage 11 – UT Dallas POEC 6382 Applied GIS Software

File Structure, pg 3 • Ramifications of File Structure in Arc/INFO: – Do not drag and drop, cut, copy, paste, delete, or rename a coverage from the NT explorer window. Any of these actions may result in corruption (and loss) of not only the coverage manipulated, but of the entire workspace. – Must use commands (see next slide for full list) in the Arc program window and within the workspace to work with coverages: • • • Arc: Arc: w m: /dlauder/tmp (move into a workspace, same as cd in DOS or UNIX) lc (list coverages - returns one called soil) copy soil c: /usr/jasper (copy to your workspace called jasper) kill soil all (deletes the coverage and info files from the workspace) rename roads txroads (gives it a new name) • Exceptions: – Can drag and drop, cut, copy, paste, and delete the entire workspace – Can drag and drop, cut, copy, paste, and delete the interchange file (e 00) created by exporting the coverage 12 – UT Dallas POEC 6382 Applied GIS Software

Commands for Workspace and Coverage Management & Exploration Coverage Management Workspace Management Listcoverages lc Workspace (go to) w Copy Createworkspace cw Kill Renameworkspace rw Rename Copyworkspace cpw Note: if a coverage folder is open Deleteworkspace dw in NT Explorer, KILL and RENAME will not work. Listworkspace lw dir info (lists “hidden” files) Coverage Exploration Describe <cover> Items <cover>. pat List <cover>. pat (basic info) (lists variable names) (lists actual data) 13 – UT Dallas POEC 6382 Applied GIS Software

Getting Online Help • There are several ways to get help for Arc/INFO commands: – Usage lines: The easiest way to display a usage line is to type in a command name without any of its arguments and then hit enter: • Arc: build • Usage: build <cover> {POLY|LINE|POINT|NODE|ANNO. <subclass>} – The USAGE command provides an alternative way of displaying a usage line. • Arc: usage build • Usage: build <cover> {POLY|LINE|POINT|NODE|ANNO. <subclass>} 14 – UT Dallas POEC 6382 Applied GIS Software

Getting Online Help, page 2 – You can display the complete or partial listings of available commands on the screen by asking for COMMANDS at any Arc prompt: • Arc: commands • Usage: commands {prefix} For commands beginning with the letter B • Arc: commands B • BATCH BUFFER BUILD – You can launch online documentation (Arc. Doc) with the help command • Arc: help 15 – UT Dallas POEC 6382 Applied GIS Software

Command Syntax Rules • Command 1 st_argument 2 nd_argument nth_argument Example: build <cover> {POLY|LINE|POINT|NODE|ANNO. <subclass>} build streets line 16 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 1 • Topology refers to Arc/INFO’s knowledge about how features are connected and which features are adjacent to each other. • Topology is a mathematical procedure that determines spatial properties and relationships, including: – length of an arc – direction of an arc – area of a polygon – connectivity of arcs – adjacency (contiguity) of polygons 17 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 2 • Topological rules: – Each arc has a beginning node and an ending node - this determines directionality. Directionality is determined during digitizing. Direction is important only if your application requires directional modeling. – Arcs connect to other arcs at nodes – Connected arcs form polygon boundaries - arc coordinates are stored only once because two adjacent polygons share the common arc between them. – Arcs have polygons on their left and right sides • Topology distinguishes Arc/INFO coverages from nontopological data models supported by many CAD, mapping and graphics systems – Shapefiles are not true topological files hence the need to covert to coverages for some analyses. 18 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 3 – Arc-node topology is how Arc/INFO keeps track of which arcs are connected to other arcs through shared nodes (nodes are endpoints of arcs). It defines length, direction, and connectivity for arcs. The from-node is an arc’s starting point; the to-node is its ending point. They are determined as you digitize your data. You can see the from-node and to-node whenever you list attribute records for a coverage containing lines. Arcs connect if they share a node. 19 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 4 – Polygon-arc topology expresses the relationship between the arc features and the polygon features for which the arcs create boundaries. It defines area and adjacency. Arcs or a set of arcs that form a closed figure define the area of a polygon. Two polygons are adjacent if they share an arc. Polygons are stored as a list of arcs to avoid redundancy. 20 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 5 – Left-right topology refers to contiguity -- how polygons are associated with their neighboring polygons. Each arc has a list of which polygons are on the right side and which are on the left side. Commands in Arc/INFO use this information to determine from one polygon what the adjacent polygons are: (see text, page 46 -49) 1 5 4 2 3 6 7 21 – UT Dallas POEC 6382 Applied GIS Software

Topology, page 6 • BUILD and CLEAN are the essential commands for creating/maintaining topology and defining/updating feature attribute tables. • You must BUILD topology after creation of a new coverage or after modifications to the coverage such as in Arc. Edit or after changing the projection. • You must CLEAN a coverage if the build command detects errors. CLEAN will correct geometric relations (thus changes spatial structure) using the parameters you specify by • adding nodes at intersections • fixing dangling nodes (if within dangle length) • Combining nodes (if within fuzzy tolerance) • BUILD only constructs topology and defines and updates feature attribute tables for a coverage. After creating a coverage you will not have attribute tables unless topology is constructed. 22 – UT Dallas POEC 6382 Applied GIS Software

Feature Attribute Tables • When Arc/INFO constructs topology for a coverage, topological and geometric properties are defined and stored in a file called a feature attribute table. Depending on the feature type (e. g. , point, arc, polygon), the contents of feature attribute tables differ; however, they all have some characteristics in common, including – Feature attribute tables are INFO data files – Each feature in a coverage occupies one record or row of data in the feature attribute table – Attribute data comprise columns (items) placed after the internally stored data – You can have more than one feature attribute table for a coverage, e. g. arcs and polygons define both streets and blocks. But you cannot have both points and polygons in the same coverage. • Common feature attribute tables: – Points - Point attribute table - PAT – Arcs - Arc attribute table - AAT – Polygons - Polygon attribute table - PAT 23 – UT Dallas POEC 6382 Applied GIS Software

Data Stored for Points • Coordinate information is stored in a LAB file. Each point is described by a single x, y coordinate pair and an internal sequence number. • A point attribute table (PAT) is created when topology is constructed for a point coverage. The PAT is used to hold the attribute data about points. There is one record (row) in the PAT for each point. The record is related to the point by the sequence number. • At a minimum the PAT contains four items – AREA Holds the area of a polygon. The value is 0 for points – PERIMETER Holds the perimeter of a polygon. The value is 0 for points – <cover># Arc/Info assigned unique internal sequence number of the point feature in the LAB. Same as RECNO - do not tamper with these values (sometimes called “pound id”) – <cover>-id User assigned unique feature ID for each point (sometimes called “dash id” or “user id”) You can add items (columns) to the PAT after the <cover>-id item. 24 – UT Dallas POEC 6382 Applied GIS Software

Data Stored for Arcs • • Coordinate information is stored in an ARC file. Each arc is described in a single record by a series of x, y coordinates, the from-node and to-node (for arcnode topology) and an internal sequence number An arc attribute table (AAT) is created when topology is constructed for an arc coverage. There is one record in AAT for each arc in the coverage. The record is related to the feature (ARC file) by the internal sequence number. At a minimum the AAT contains seven items – FNODE# Internal sequence number of the from-node – TNODE# Internal sequence number of the to-node – LPOLY# Internal sequence number of the left polygon; set to 0 if the coverage does not have polygon topology – RPOLY# Internal sequence number of the right polygon; set to 0 if the coverage does not have polygon topology – LENGTH Length of the arc in coverage units – <cover># Arc/Info assigned unique internal sequence number of the arc in the ARC file. NEVER modify this value. – <cover>-id User assigned unique feature ID for each arc You can add items (attributes) to the PAT after the <cover>-id item. 25 – UT Dallas POEC 6382 Applied GIS Software

Data Stored for Polygons (PAT) • A polygon is defined by the arcs comprising its border and interior islands, with polygon-arc topology stored in the PAL file, and arcnode/left-right topology stored in the ARC file, and a label point inside the polygon stored in the LAB file. The label point id identifies the polygon and is consistent between files. • A polygon attribute table (PAT) is created when topology is constructed for a polygon coverage. The PAT is used to hold the attribute data about polygons. There is one record in the PAT for each polygon. The record is related to the polygon by the label point id. • At a minimum the PAT contains four items (same as point attrib table) – AREA Holds the area of a polygon, in coverage units. – PERIMETER Holds the perimeter of a polygon. The value is 0 for points – <cover># Arc/Info assigned unique internal sequence number of the polygon feature in the LAB, ARC and PAL files – <cover>-id User assigned unique feature ID for each point You can add items (attributes) to the PAT after the <cover>-id item. • The first polygon is always the universal polygon which represents the coverage boundary. 26 – UT Dallas POEC 6382 Applied GIS Software

Polygon data stored in PAT 27 – UT Dallas POEC 6382 Applied GIS Software

Overview: Feature Attribute Tables • Types of feature attribute tables: – Points - Point attribute table - PAT – Arcs - Arc attribute table - AAT – Polygons - Polygon attribute table - PAT Each contain both internally generated topological data plus user defined attributes • For general information on coverage (projection, etc. ) – Arc: describe <cover> • To look at data variables (items) in a feature attribute table: – Arc: items <cover>. pat(for point or polygon) – Arc: items <cover>. aat (for arcs) • To look at data stored in each item – Arc: list <cover>. pat – Arc: list <cover>. aat Note: items and list require you to specify the extension. pat, . aat 28 – UT Dallas POEC 6382 Applied GIS Software

Sample Item Definitions • Example: Arc: items pub. pat COLUMN ITEM NAME 1 AREA 5 PERIMETER 9 PUB# 13 PUB-ID 17 ID 25 NAME 50 ADDRESS 65 CITY WIDTH OUTPUT TYPE N. DEC 4 12 F 3 4 5 B 8 12 F 0 25 25 C 15 15 C 12 12 C - • See text page 101 for greater clarification. 29 – UT Dallas POEC 6382 Applied GIS Software

Understanding Item Definitions • An item (column) is described in terms of four variables: – name - the name of the item, up to 16 characters in length • e. g. cover-id, landuse, pop 97, etc. – type - the data types used to store values • • • I - integer (one byte per digit) B - binary integer (requires less storage than I types) C - character N - floating point (e. g. decimal) number stored as one byte per digit F - floating point binary number D - date (e. g. yyyymmdd) – width - the width of the item in bytes required for storage • I - 1 -16 bytes B - either 2 or 4 bytes • C - 1 to 320 characters N - 1 to 16 digits • F - 4 for single, 8 for double precision D - always 8 bytes For F or N also provide the number of decimal places for real numbers – Output width - the width of item values when displayed 30 – UT Dallas POEC 6382 Applied GIS Software

A Review of Item Definitions Maximum 4 byte binary is 2, 147, 483, 648; maximum 4 byte integer is 9, 999 31 – UT Dallas POEC 6382 Applied GIS Software

List • To look at data stored Arc: list lulcsp. pat 1 AREA PERIMETER LULCSP# LULCSP-ID LULC_CODE LEVEL_II 2 AREA PERIMETER LULCSP# LULCSP-ID LULC_CODE LEVEL_II = ****** = 26829452. 50 = 1 = 0 = = =12154654112 = 3137822. 500 = 21 = AGRICULTURAL LAND = CROPLAND/PASTURE 3 AREA PERIMETER LULCSP# LULCSP-ID LULC_CODE Continue? LEVEL_II 4 AREA PERIMETER LULCSP# LULCSP-ID LULC_CODE LEVEL_II 5 AREA PERIMETER LULCSP# LULCSP-ID LULC_CODE LEVEL_II = 11278215. 000 = 17881. 912 = 3 = 41 = FOREST LAND = DECIDUOUS FOREST = 2316684. 250 = 6632. 658 = 4 = 11 = URBAN OR BUILT-UP = RESIDENTIAL = 7348584. 000 = 12674. 189 = 5 = 41 = FOREST LAND = DECIDUOUS FOREST 32 – UT Dallas POEC 6382 Applied GIS Software