Update (Coverage) (ArcInfo only)

Usage tips

• Before using UPDATE, the following conditions must be met:

  • Item definitions past the User-ID must be the same for the input and update coverages. This includes redefined items.
  • Annotation subclasses and their attribute definitions must be identical. Blank annotation subclasses are ignored.
  • Section subclasses and their attribute definitions must be identical.
  • Region subclasses with the same name must have the same attribute definitions.

• The input coverage and the update coverage must have polygon topology.

• The item definitions for items past the User-ID in the input coverage and update coverage feature attribute tables must match exactly, including redefined items. The input coverage and update coverage items are joined to the output coverage attribute table using the old polygon internal number as the relate item.

• New label point positions are only generated for the output coverage polygons when necessary. The User-ID for each polygon is equal to its old input coverage User-ID (the update coverage User-ID for updated polygons). Thus, you should attempt to make the User-ID values in the input coverage different from User-ID values in the update coverage to avoid having duplicate User-IDs in the output coverage.

• UPDATE maintains all route system subclasses. If a Section (SEC) subclass is present on either coverage, then it must be present on both, and it must have identical item definitions. Route systems attached to update arcs are retained. Route systems attached to input arcs are retained if they survive. UPDATE manages route systems like an Erase, followed by an Append, then a Clean.

• If DROP_BORDER is used, polygon boundaries along the outer edge of the update coverage are dropped. Even though the outer boundaries of some update polygons are dropped, the item values for the update polygons that overlap input coverage polygons will be assigned to the polygons in the output coverage. The DROP_BORDER option is not recommended for region coverages because of the possibility that some output regions may not be maintained.

• Annotation features are updated by identifying and deleting the set of input coverage annotation whose lower left starting points fall within an update coverage polygon. Update coverage annotation is then appended for all annotation subclasses present to the output coverage. Both coverages must have identical sets of annotation subclasses with the exception of blank annotation classes, which can be either present or absent. Where subclasses have attributes, they must have identical attribute definitions.

• If the update coverage contains nodes on its border that are coincident with nodes in the input coverage, the update coverage nodes are maintained. The only exception is if the input coverage node contains data in the NAT and the update coverage node does not have an NAT.

• Region subclasses are updated with both the POLY and NET options. All regions are maintained with the KEEP_BORDER option only. The DROP_BORDER option does not maintain all regions and, therefore, is not recommended when updating region coverages.

• The input coverage and update coverage region subclasses may be the same or different. When the subclasses are the same, they must have the same item definitions.

• The coordinate precision of the output coverage is determined by the Precision for Derived Coverages environment.

• Projection files will be compared for similarity using the level of comparison specified in the Compare Projections environment.

• Learn more about data model content inherited by the output

• Learn more about how the default fuzzy tolerance is calculated

• Learn more about processing planar graphs

• The following environments affect this tool: derivedPrecision, newPrecision, projectCompare, scratchWorkspace, and current workspace.

Command line syntax
An overview of the Command Line window
Update_arc <in_cover> <update_cover> <out_cover> {POLY | NET} {fuzzy_tolerance} {KEEP_BORDER | DROP_BORDER}

Command line example

update_arc city_lots flood_levels low_lots POLY 0.0003 DROP_BORDER

Scripting syntax
About getting started with writing geoprocessing scripts
Update_arc (in_cover, update_cover, out_cover, feature_type, fuzzy_tolerance, keep_border)

Script example

# SimpleUpdate.py
# Description: Simple example of using Update in a python script
# Requirements: Python and the Python win32all extension
# Author: ESRI
# Date 1/1/2004

# Create the Geoprocessor
import arcgisscripting
gp = arcgisscripting.create()

# Put in error trapping in case an error occurs when running tool
try:
    # Update the parcels with parcelsNew coverage
    gp.workspace = "c:/work/gisdata"
    gp.Update_arc("parcels", "newparcels","parcels2")

except:
    # If an error occurred print the message to the screen
    print gp.GetMessages()