Esrm 250 cfr 520 autumn 2009 phil hurvitz
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ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz PowerPoint PPT Presentation


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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

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Creating Feature Datasets(vector data)

ESRM 250/CFR 520Autumn 2009

Phil Hurvitz

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


tedious & detail-oriented work

Digitizing

  • most common “legacy” method of getting data into a GIS


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

  • ArcGIS supports creation & editing of vector data sets (shapefile & geodatabase = “feature class”)

    • Point

    • Line

    • Polygon

  • Data sets are completely editable

    • Coordinate data

    • Attribute data


CAD data

Converting to feature class

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


Converting to feature class

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

shapefile or gdb feature class


Converting to feature class

  • Selected sets are converted


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 datasets

  • New datasets can be created from scratch in ArcCatalog

    • specify coordinate system


Creating new datasets: “heads-up” digitizing

  • Done completely on computer (no digitizing tablet), hence the term “heads-up”


Creating new datasets

  • Create a road layer using a photo background


Creating new datasets

  • New features can be created from tracing existing selected features


Snapping

  • Snapping controls:

    • how features align during creation/editing

    • connections of lines (node placement)

    • completion of polygons

    • avoid overshoots/undershoots

    • avoid slivers or gaps


Snapping

  • Snapping behavior controlled by the Snapping Environment dialog


Snapping


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


Snapping

  • Helps avoid these errors

J. Lawler


Altering the shape of lines and polygons

  • Topological editing: shared edges are all affected by edits


Altering the shape of lines and polygons

  • Non-topological editing: only a single feature is edited


Splitting (cutting) polygons

  • Polygons are split by a user-defined line


Splitting lines

  • Lines are split at a specified location


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)


image from ESRI

Splitting features

  • Attribute splitting (for geodatabase feature classes) is handled by policies


Merging polygons

select multiple polygons from the same layer

original polygons are merged into a single new polygon


Merging polygons

  • Attributes are handled by rules in the same way as splitting

image from ESRI


Merging polygons

  • Merging polygons: an example

J. Lawler


Unioning polygons

  • Similar to merge, but can combine features from > 1 layer


Intersecting polygons

like mathematical intersection

spatial area as the "set" for intersection

a new polygon from common areas


Clipping polygons

Option 1: discard the intersection


Clipping polygons

Option 2: keep only the intersection


Clipping: an example

J. Lawler


Clipping: an example

J. Lawler


Clipping: an example

  • Landscape metrics calculated from clipped frog home range

% forest 73

% ag12

Ag dist20

F-patch.s60

A-patch.s6

J. Lawler


Adding attributes

  • Attributes need to be defined for new datasets

    • Fields are added; define

      • field name

      • data type

      • width

      • decimal precision


Adding attributes

  • Adding & defining fields: note field names & data types


Adding attributes

  • After fields are added, attributes can be updated


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

  • 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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