COLLAPSE2

Typify polygons.  Polygons with a perimeter less than a specified length will either be removed or collapsed into a centerline.  Polygons that are not connected to any arcs in the <in_line_cover> are removed.  Polygons that are connected to one or more arcs in the <in_line_cover> are centerlined.  Connectivity with the <in_line_cover> is maintained.

__________________________________________________________________________

COLLAPSE2 <in_poly_cover> <in_line_cover> <out_poly_cover> <out_line_cover> <in_poly_item> <in_line_item> <out_poly_item> {max_perimeter} {cellsize} {weed_tolerance} {spline_tolerance} {dangle_length} {fuzzy_tolerance}

ARGUMENTS

<in_poly_cover> - the input polygon coverage whose polygons are to be typified.

<in_line_cover> - the input line coverage whose lines are connected to the polygons in the <in_poly_cover>.

The connectivity between these lines and the collapsed polygons will be maintained.

<out_poly_cover> - the name for the output polygon coverage.

This coverage contains polygons that were not typified.

Unlike the COLLAPSE tool, COLLAPSE2 does not generalize the boundaries of the polygons in the <out_poly_cover>.

WARNING - The output polygon boundaries are also written to the <out_line_cover>.  At this time the boundaries in these two coverages will not always match exactly.  Deviation occurs where the <out_line_cover> boundaries are snapped to <in_line_cover> arcs to maintain connectivity.

<out_line_cover> - the name for the output line coverage.

This coverage contains the collapsed centerlines and the boundaries of polygons that were not typified.

The collapsed centerlines are attributed `405' (intermittent) if any connecting arcs from the <in_line_cover> are attributed `405', otherwise the centerlines are attributed `402' (perennial.)

The attribute of each collapsed centerline is stored in an item named <out_item> with a `1' suffix, e.g. CFF1.  The attribute of each polygon boundary is also stored in an item named <out_item> with a `1' suffix.  In the event that a polygon boundary is shared by adjacent polygon, the second attribute is stored in an item named <out_item> with a `2' suffix, e.g. CFF2.

WARNING - The centerlines will not always fall inside of the original polygon boundaries.  The smaller the {cellsize}, the less likely it is that the centerlines will not fall inside of the original boundary.

WARNING - The output polygon boundaries are also written to the <out_poly_cover>.  At this time the boundaries in these two coverages will not always match exactly.  Deviation occurs where the <out_line_cover> boundaries are snapped to <in_line_cover> arcs to maintain connectivity.

<in_poly_item> - the input item in the <in_poly_cover> PAT that identifies the type of each polygon, e.g. CFF code.

<in_line_item> - the item in the <in_line_cover> AAT that identifies whether arcs are perennial or intermittent.

An <in_line_item> value of `405' is considered intermittent.  All other codes are considered perennial.

<out_poly_item> - the name for the output item in the <out_poly_cover> PAT.

This named is also used as the prefix for two items in the <out_line_cover> AAT.  The suffixes are `1' and `2', e.g. CFF1 and CFF2.  These items contain the attribute of the polygons on each side of the boundary.

{max_perimeter} - the maximum perimeter of polygons that are to be typified.

If not specified it defaults to 800 meters.

Polygons with a perimeter less than the {max_perimeter} will either be removed or collapsed into a centerline.  Polygons that are not connected to any arcs in the <in_line_cover> are removed.  Polygons that are connected to one or more arcs in the <in_line_cover> are centerlined.

{cellsize} - the size of the grid cells used to do the processing.

COLLAPSE converts the <poly_cover> into a temporary grid in order to collapse polygons.

If {cellsize} is not specified, it defaults to 1/1000 of the maximum dimension of the BND of the <in_poly_cover>.

{weed_tolerance} - the weed tolerance used during generalization of polygon centerlines.

If not specified it defaults to the {cellsize}.

{spline_tolerance} - the initial GRAIN size used during generalization of polygon centerlines and boundaries.

If not specified it defaults to zero.

If the {spline_tolerance} equals zero, then no splining takes place.

{dangle_length} - the minimum allowable dangle length for the <out_line_cover>.

Dangles less than this length will be deleted.  Dangles are created where there are polygon lobes but no attachment to arcs in the <in_line_cover>, e.g. inlets in a water body with no stream attached to the inlet.

If not specified it defaults to the {max_perimeter} divided by 2*PI.

{fuzzy_tolerance} - the fuzzy tolerance for the output coverages.

If not specified it defaults to the fuzzy tolerance of the <in_poly_cover>.

NOTES

COLLAPSE2 runs from the ARC module of ArcInfo.

COLLAPSE2 uses three C programs that have been compiled for both Win2K and IBM AIX UNIX machines.

EXAMPLES

Arc: &run collapse2 usage

Usage: COLLAPSE2 <in_poly_cover> <in_line_cover> <out_poly_cover> <out_line_cover> <in_poly_item> <in_line_item> <out_poly_item> {max_perimeter} {cellsize} {weed_tolerance} {spline_tolerance} {dangle_length} {fuzzy_tolerance}

1)  To typify lakes, reservoirs, and stock ponds less than 800 meters around, using a 3-meter cell size:

Arc: &run collapse2 hydro_poly hydro_line hydro_poly2 hydro_line2 ~ Arc: cff cff1 cff 800 3