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ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz

Creating Feature Datasets (vector data). ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz. Overview. Unioning polygons Merging polygons Intersecting polygons Clipping polygons Adding attributes Undoing edits Saving edits. Digitizing Creating vector data sets Converting to feature class

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ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz

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  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

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