esrm 250 cfr 520 autumn 2009 phil hurvitz
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ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz

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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
Creating Feature Datasets(vector data)

ESRM 250/CFR 520Autumn 2009

Phil Hurvitz

2

overview
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
digitizing
tedious & detail-oriented workDigitizing
  • most common “legacy” method of getting data into a GIS
digitizing tablet

y = 10

operatorclicks on or traces features

x = 5

Digitizing tablet
  • How the digitizing tablet works

coordinates are placed in database

creating vector data sets
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
converting to feature class

CAD data

Converting to feature class
  • Any supported vector data set can be converted to feature class
converting to feature class1
Converting to feature class
  • Any supported vector data set can be converted to feature class

shapefile or gdb feature class

converting to feature class2
Converting to feature class
  • Selected sets are converted
creating new datasets

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
creating new datasets1
Creating new datasets
  • New datasets can be created from scratch in ArcCatalog
    • specify coordinate system
creating new datasets heads up digitizing
Creating new datasets: “heads-up” digitizing
  • Done completely on computer (no digitizing tablet), hence the term “heads-up”
creating new datasets2
Creating new datasets
  • Create a road layer using a photo background
creating new datasets3
Creating new datasets
  • New features can be created from tracing existing selected features
snapping
Snapping
  • Snapping controls:
    • how features align during creation/editing
    • connections of lines (node placement)
    • completion of polygons
    • avoid overshoots/undershoots
    • avoid slivers or gaps
snapping1
Snapping
  • Snapping behavior controlled by the Snapping Environment dialog
snapping options
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
snapping3
Snapping
  • Helps avoid these errors

J. Lawler

altering the shape of lines and polygons
Altering the shape of lines and polygons
  • Topological editing: shared edges are all affected by edits
altering the shape of lines and polygons1
Altering the shape of lines and polygons
  • Non-topological editing: only a single feature is edited
splitting cutting polygons
Splitting (cutting) polygons
  • Polygons are split by a user-defined line
splitting lines
Splitting lines
  • Lines are split at a specified location
splitting features
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)
splitting features1

image from ESRI

Splitting features
  • Attribute splitting (for geodatabase feature classes) is handled by policies
merging polygons
Merging polygons

select multiple polygons from the same layer

original polygons are merged into a single new polygon

merging polygons1
Merging polygons
  • Attributes are handled by rules in the same way as splitting

image from ESRI

merging polygons2
Merging polygons
  • Merging polygons: an example

J. Lawler

unioning polygons
Unioning polygons
  • Similar to merge, but can combine features from > 1 layer
intersecting polygons
Intersecting polygons

like mathematical intersection

spatial area as the "set" for intersection

a new polygon from common areas

clipping polygons
Clipping polygons

Option 1: discard the intersection

clipping polygons1
Clipping polygons

Option 2: keep only the intersection

clipping an example2
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

adding attributes
Adding attributes
  • Attributes need to be defined for new datasets
    • Fields are added; define
      • field name
      • data type
      • width
      • decimal precision
adding attributes1
Adding attributes
  • Adding & defining fields: note field names & data types
adding attributes2
Adding attributes
  • After fields are added, attributes can be updated
undoing edits
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
saving edits
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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