Extra Materials

1. Extra Materials Introduction to ArcWorkstation

2. What’s it look like? • Traditionally a UNIX based “command line interface” package… • Ran on UNIX machines. • You typed in commands, and it showed you the results in another simple window.

3. What’s ArcWorkstation made up of? • Made up of separate modules that communicate with each other. The command line interface is… Arc: core application for doing analysis, and using “workspaces” where all the files are kept for each project. ArcEdit: for editing maps interactively. ArcPlot: for neat plotting of maps. ArcTools: Pre-made AML scripts Grid: for working with image files/raster data. (Might also see on older systems: ArcTIN: 3D work; ArcPress: printing; ArcStorm: multiuser databases; ArcNetwork: networks).

4. What is ArcWorkstation? • You can think of it as two main bits… • ARC – the starting program where most stuff is done. • INFO – a database, which holds tables of related information, all tagged with a geographical location. • Lets you analyse the database data using a map interface, and display the results as a map.

5. Why bother with it? • Because: • ArcGIS 8/9.x doesn’t have the functionality of ArcWorkstation, and plenty of places still use it. • There is still a lot of use of legacy AML code. • There is still a lot of data floating around in Coverages. • We’ll teach you enough to understand how it works and give you a foundation to work from if you come across it.

6. The ArcInfo Data Model • Store all the same types of features in one file using x,y coordinates… • i.e. all the point features in one file, all the line features in another file, and all the associated non-location data in yet another file. • Makes storage and handling easier. • Makes analysis easier. • The filenames show what kind of data they hold. • e.g. Label Points are stored in a LAB (lab.adf) file.

7. Storing Data

8. Storing Vector data • The files hold coordinate data and Feature Numbers that are assigned sequentially to Features in the file.

9. Tics • Tics – geographical control points used to register (overlap) different datasets, and transform (eg. put in a new projection scheme) the data. • For example, you might mark in known locations on two datasets, usually at the data edges, as Tics. • Stored in a TIC file (tic.adf).

10. Arcs • Arcs - stored in an ARC file (arc.adf). • A point where an Arc changes direction is called a “Vertex”. • The start and ends of Arcs, and the crossing point between two Arcs, are called “Nodes”. • The ARC file stores each Vertex and Node as an x,y coordinate. Data can be assigned to Nodes

11. Polygons • An area - can also have “islands” inside, that cut out inner areas. • Made from one (or more) Arcs. • The end Node is the same as the starting one. • Each also has a Label Point (x,y) associated with it, stored in a LAB file. +42

12. Polygon-Arc List • The Polygon-Arc List file (pal.adf) stores which Arcs make up each Polygon. That way we don’t need to store the Arc coordinates again. ARC PAL #1 #2 +23 #3

13. Polygon-Arc List • The outside or “Universe” Polygon is always feature number 1, ie. first in the PAL file. • Islands start with a zero, followed by the Arcs.

14. Topology • Analysis we might want to do… • “How do I move from Arc to Arc to get from A to B fastest?” • “If I leave Polygon A going north, which Polygon do I enter?” • To do these analyses we need some notion of Topology, ie. the spatial relationships between features.

15. Topology in ArcInfo • Three ways topology is defined in ArcInfo… • Arcs connect at Nodes. • Arcs have direction, and therefore a left and right side. • Arcs that connect to surround an area make a Polygon.

16. How Topology is stored Note that polygons are listed clockwise in the PAL, with minus figures for reverse direction Arcs. • Stored in the files. N2 PAL +23 N1 N3 ARC/ATT

17. Feature Attributes • Info stores information about each feature in a Feature Attribute Table using the Feature Number to match the attribute data to the coordinates in the other files in a one-to-one relationship. Each data type has its own table type. • Each feature will also have a unique User Defined ID kept in its table in addition to its Feature Number. PAL FAT

18. Types of Feature Attribute Table • Label Points / Polygons – Point/Polygon Attribute Table (PAT / pat.adf file). • Includes AREA and PERIMETER columns with the values associated with any Polygons for which the Points are labels. • Can be used to hold points or Polygon labels, but not both. • Arcs – Arc Attribute Table (ATT / att.adf file). • Includes FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH columns. • When Nodes have data associated with them - Node Attribute Table (NAT / nat.adf file). • Includes an ARC# column referencing one of the Arcs.

19. Feature Attribute Table Format • After the columns listed above usually come the Feature Number (NAME#) and the User Defined ID (NAME-ID) columns. • Following these, users can then create more columns to hold attribute data.

20. Example PAT • Note that the Universe Polygon is first, and the AREA given for it is the negative total of the rest.

21. Other Vector data • Region – several related Polygons, nested or overlapping. Stored in a PAT.regionName (pat.adf file). • Annotation – text drawn along an associated feature. Stored in a T(ext)AT (txt.adf file). • Section – an Arc / portion of Arc representing a part of a pathway. Stored in a SEC table (sec.adf file). • Route – a pathway made out of multiple Sections. Stored in a R(oute)AT (rat.adf file).

22. Putting features together • So, we’ve seen that individual features are stored in files with similar types (eg. all the line features in a file of Arcs). • When these are combined, you get a data “Coverage”. A Coverage usually contains one type of geographical information or analysis result, eg. “Geology”, “Roads”, or “Quickest routes” • Several Coverages may go together in a map, and you can turn different ones on and off to display different facets of a map.

23. Coverages • In the file system, these are represented as the directories your data files go in. • They let you keep data files together and display them at the same time. • Usually it is the name of the Coverage that goes to form the Feature Number and ID column names. • Eg. The SOILS coverage before gave our example PAT a SOILS# Feature Number column and a SOILS-ID column.

24. Addition Coverage information • As well as our data files, a Coverage will have several other pieces of information associated with it. • A Coverage Extent (BND / bnd.adf file) - this records the upper right and lower left corners of a rectangle containing all the feature data in the Coverage. It need not contain all the Tic and Annotation points. • A Coordinate Definition file (PRJ / prj.adf ) - holds the Coverage’s map projection information • A Tolerances file (TOL / tol.adf ) - holds a number of processing tolerances, eg. How close Tics in different files need to be before they count as matching.

25. Putting Coverages together • Finally Coverages can be kept together in project areas called “Workspaces”. • Workspaces allow you to keep all the data and Coverages you generate for a project in one place, separate from any other work you may be doing. • In the file system they’re represented as directories which include all the Coverage directories you’re working on in a project. • One of the first things you do on starting any ArcWorkstation project is move to your present Workspace.

26. The Vector Data Model Filesystem ArcCatalog • Different views of the same data. Workspace Coverages Vector data Raster data TIN data

27. Summary • Vector data includes Label Points, Arcs, Polygons and Tics. • The coordinates for the features of each type are stored in separate files, one file for each type. • Within the files, each individual feature has a Feature Number and a set of coordinates. • The Feature Number is used to link features to attribute data stored in a Feature Attribute Table of a particular type. • You can get at the combined data through their representation as Tables in ArcWorkstation.

28. Summary • Data stored in separate files / tables can be combined to form Coverages. • Coverages usually contain information about a single landuse or analysis result. • All the Coverages in a project can be kept together in a Workspace. • Coverages and Workspaces are represented as directories in the file system.

29. ArcCatalog • It is vital that you never alter the file names or location outside of the ArcGIS applications. • You can get at most of the information in the files and change/move/delete them in ArcGIS. • The best way to do these operations is in ArcCatalog. • We looked at some of the functions of ArcCatalog in the last practical. We’ll add a bit more detail now.

30. Navigating • ArcCatalog starts up displaying your harddrive, but you can add additional drives. • You can add online databases if they hold appropriate data. • Databases are a whole other course! Check ArcCatalog Help files for more details!

31. Data viewing • Can view Coverages in a number of ways.

32. Metadata • “Data about Data”. • Where it’s from and what’s happened to it. • Who made it and what’s its problems. • What does it contain, and how. • ArcCatalog lets you see and change metadata for… • Describing the data and where it’s from. • Describing the spatial data form and projection etc. • Describing the attributes associated with the data. • Double-click on a metadata element to open up the metadata form. • The metadata is in the Coverage’s metadata.xml file. • XML is a markup language like HTML. You can open it in Internet Explorer if you want to see what it looks like.

33. Altering and copying Coverages • You can use ArcCatalog as if it were Windows Explorer to rename, delete, copy or move Coverages and other data items, and make new folders. • You use exactly the same keys/menus as you would in Explorer. Most menu options can be got at by right-clicking on a folder or file. • The only difference is that ArcCatalog simultaneously goes through and updates all the files ArcGIS needs to keep track of what’s happened to the data.

34. Making a Workspace • Making a new Workspace is as easy as making a new folder. • File > New > ArcInfoWorkspace (or right-click > New > ArcInfo Workspace) • Rename the Workspace appropriately. • If you look in Explorer, you’ll see an Info directory has been made in the Workspace directory to store related information.

35. Making a Coverage • Making a Coverage is almost as easy, but requires slightly more thought. • File > New > Coverage… • This brings up a “Wizard” (set of instructional forms to fill in) to help you.

36. Name the Coverage • You can use an existing coverage to supply boundary, tic and projection information.

37. Fix the projection • If you don’t supply a template, you’ll need to say what projection scheme it’s in, or pick none.

38. Generate initial topology • If you know which feature type will be important, you can generate the appropriate feature table.

39. Other ways of manipulating files and Workspaces • Command line from Arc (the web version of this lecture has equivalent notes for ArcWorkstation). • Using any of the ArcTools. • ArcTools is a set of AML routines with menus for doing tricky Arc tasks.

40. Summary • Never alter the files or directories outside of ArcGIS. • The easiest way to alter, delete or move ArcGIS data is with ArcCatalog. It acts like Explorer, but informs Arc what it’s doing. • You can manipulate data and directories using Arc or ArcTools.

41. Cleaning in ArcCatalog • Right-click on the Coverage > Properties • General > clean

42. X 200 Fuzzy Tolerance • Fuzzy Tolerance : the distance up to which points will be considered the same and snapped to the same point. • This helps eliminate slithers. • Should be small (~1/100,000 BDN rectangle size). If too small an automatic value is given (see ArcDocs). X 200 x 1 uncleaned cleaned

43. Dangles • Dangle Length : any overshooting Arc longer than this won’t be removed as an error. • Usually zero for Arc Coverages, 0.05 inches (0.127 cm) for Polygons. • Note that Tolerances can be set in the Coverage properties before this time (sets the TOL Table / file). X 200 X 200 x 1 uncleaned cleaned

44. Building in ArcCatalog • After cleaning, hit the build button to build the Topology. • At this point you can decide what Topology to build. • Just because you digitised as Polygons doesn’t mean you can’t make a set of Arcs or Nodes here for your Coverage. The Polygons will be split or Nodes extracted as appropriate.

45. Building in ArcCatalog • Once you have your new Features (Arcs from Polygons, for example) you can go back into ArcMap and edit / delete bits using the EditorSelect tool.

46. Editing - ArcEdit • By and large, not much point in using it now. • However, there are a few useful commands if you can seem to clean/build your topologies. • nodeerrors • Lists Arc undershoots, overshoots and open Polygons. • labelerrors • Lists where Polygons are associated with multiple labels. This should only be a problem if importing a Coverage previously produced in ArcWorkstation.

47. Error marks • Errors are marked at the Nodes where there’s a problem. Note that pseudo-Nodes (Arc crosses or Arcs join to themselves) show as diamonds. These are ok, except where they show a missing Arc i.e. two labels in one Polygon. Overshoot Overshoot Undershoot Open Polygon Missing Arc

48. Exporting • The same ArcToolbox conversion tools let you export Coverages as different formats. Also the Arc export command. • Should always clean and build before exporting. • Supported formats include… • “Generate” (.gen) ASCII files. • Interchange “e-naught-naught” (.e00) files – a popular way of transfering ArcGIS Coverages – esp. UNIX to NT and vice versa. Includes all the information necessary.

49. Data manipulation

50. Coverage Feature Attribute Tables • Info stores information about each feature in a Feature Attribute Table using the Feature Number to match the attribute data to the coordinates in the geography files in a one-to-one relationship. Each data type has its own table type. PAL FAT