ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz

1. Creating Feature Datasets(vector data) ESRM 250/CFR 520Autumn 2009 Phil Hurvitz 2

2. Overview • Unioning polygons • Merging polygons • Intersecting polygons • Clipping polygons • Adding attributes • Undoing edits • Saving edits • Digitizing • Creating vector data sets • Converting to feature class • Creating new datasets • Snapping • Altering the shape of lines and polygons • Splitting features

3. tedious & detail-oriented work Digitizing • most common “legacy” method of getting data into a GIS

4. y = 10 operatorclicks on or traces features x = 5 Digitizing tablet • How the digitizing tablet works coordinates are placed in database

5. Creating vector data sets • ArcGIS supports creation & editing of vector data sets (shapefile & geodatabase = “feature class”) • Point • Line • Polygon • Data sets are completely editable • Coordinate data • Attribute data

6. CAD data Converting to feature class • Any supported vector data set can be converted to feature class

7. Converting to feature class • Any supported vector data set can be converted to feature class shapefile or gdb feature class

8. Converting to feature class • Selected sets are converted

9. select feature type Creating new datasets • New datasets can be created from scratch in ArcCatalog • decide in advance what feature type to represent the data

10. Creating new datasets • New datasets can be created from scratch in ArcCatalog • specify coordinate system

11. Creating new datasets: “heads-up” digitizing • Done completely on computer (no digitizing tablet), hence the term “heads-up”

12. Creating new datasets • Create a road layer using a photo background

13. Creating new datasets • New features can be created from tracing existing selected features

14. Snapping • Snapping controls: • how features align during creation/editing • connections of lines (node placement) • completion of polygons • avoid overshoots/undershoots • avoid slivers or gaps

15. Snapping • Snapping behavior controlled by the Snapping Environment dialog

16. Snapping

17. Snapping options • Interactive snapping options • Snap to an existing vertex • Snap to an existing line segment or polygon edge • Snap to an intersection of two or more lines • Snap to an existing line endpoint • Snapping can be layer-to-layer

18. Snapping • Helps avoid these errors J. Lawler

19. Altering the shape of lines and polygons • Topological editing: shared edges are all affected by edits

20. Altering the shape of lines and polygons • Non-topological editing: only a single feature is edited

21. Splitting (cutting) polygons • Polygons are split by a user-defined line

22. Splitting lines • Lines are split at a specified location

23. Splitting features • Geodatabase splitting policies • Attributes are handled by policies • Duplicate: values in new records are copied from the parent record • Geometry property (e.g., area, perimeter, length) automatically handled • Geometry ratio • based on geometry (e.g., percent of area)

24. image from ESRI Splitting features • Attribute splitting (for geodatabase feature classes) is handled by policies

25. Merging polygons select multiple polygons from the same layer original polygons are merged into a single new polygon

26. Merging polygons • Attributes are handled by rules in the same way as splitting image from ESRI

27. Merging polygons • Merging polygons: an example J. Lawler

28. Unioning polygons • Similar to merge, but can combine features from > 1 layer

29. Intersecting polygons like mathematical intersection spatial area as the "set" for intersection a new polygon from common areas

30. Clipping polygons Option 1: discard the intersection

31. Clipping polygons Option 2: keep only the intersection

32. Clipping: an example J. Lawler

33. Clipping: an example J. Lawler

34. Clipping: an example • Landscape metrics calculated from clipped frog home range % forest 73 % ag 12 Ag dist 20 F-patch.s 60 A-patch.s 6 J. Lawler

35. Adding attributes • Attributes need to be defined for new datasets • Fields are added; define • field name • data type • width • decimal precision

36. Adding attributes • Adding & defining fields: note field names & data types

37. Adding attributes • After fields are added, attributes can be updated

38. Undoing edits • Edits can be undone in reverse order • Edits can be undone up to the previous save (or creation) • Once a dataset’s changes are saved, edits cannot be undone • It can be good to have a backup of the data created before an editing session

39. Saving edits • Save EARLY and OFTEN • You are prompted to save edits when: • Dataset is closed for editing • Another dataset is opened for editing • Document is saved or closed • ArcGIS is closed