Delineate Built-Up Areas (Cartography)
Summary
Creates polygons to represent built-up areas by delineating densely clustered arrangements of buildings on small-scale maps.
The boundaries—or edges—of the output polygons can be dictated by the location of other features such as roads or hydrology. Input buildings can be attributed to identify which can be replaced in maps by the built-up area polygons for a more generalized depiction.
Illustration
 |
Usage
-
Input buildings are clustered together based on the Grouping Distance parameter to define dense arrangements of buildings that can be represented by a single built-up area polygon for smaller-scale display. Run the tool on the same input features with a different grouping distance to produce polygons representing different degrees of building grouping that can be used for display at differing scales or even shown together at a single scale.
Use Edge Features to align the edges of built-up area polygons to other features displayed in the same map, such as roads or administrative areas. Polygon outlines snap only to those features that are generally trending in the same direction as the polygon edge and within the grouping distance away.
Use Identifier Field to identify buildings that were considered in the formation of the built-up area polygons. When displaying built-up areas at midscale ranges, you might want to use a definition query on the building layers to draw only those buildings not represented by a built-up area.
To create a more simplified set of built-up area polygons for use at an even smaller scale, consider running the tool again, this time using the output built-up area polygons as the input layer. Use a larger Minimum Detail Size value to reduce the complexity of the polygons and a different edge features value (corresponding to features that will be drawn on the smaller-scale map), if applicable. Set the Minimum Building Count value to 1 in this case to ensure that all polygons are considered.
The output feature class includes a field called bldg_count, which tells you how many buildings are replaced by each built-up area polygon. Use this field in a layer definition query to limit the display of built-up area polygons to only those that represent a minimum number of buildings.
When point buildings are used as inputs, the edges of the resulting built-up area polygons may cross symbolized point buildings when drawn at scale. If this is undesirable, consider using the attributes in the identifier field to help identify buildings that fall near the edges of the built-up area polygons to filter them from display.
Syntax
| Parameter | Explanation | Data Type |
in_buildings [in_buildings,...] |
The layers containing buildings whose density and arrangement are used to define appropriate output built-up polygons. Multiple building layers can be assessed simultaneously. Building features can be points or polygons. | Feature Layer |
identifier_field (Optional) |
A field on the input feature classes that will hold a status code indicating whether the input feature is part of the resulting built-up area . This field must be either short or long integer type and common in all input layers, if multiple input layers are used.
| String |
out_feature_class |
The output feature class containing built-up area polygons representing clustered arrangements of input buildings. | Feature Class |
grouping_distance |
Buildings closer together than the grouping distance are considered collectively as candidates for representation by an output built-up area polygon. This distance is measured from the edges of polygon buildings and the centers of point buildings. | Linear unit |
minimum_detail_size |
Defines the relative degree of detail in the output built-up area polygons. This roughly translates to the minimum allowable diameter of a hole or cavity in the built-up area polygon. The actual size and shape of holes and cavities within the polygon is determined also by the arrangement of the input buildings, the grouping distance, and the presence of edge features, if they are used. | Linear unit |
edge_features [edge_features,...] (Optional) |
The layers that can be used to define the edges of the built-up area polygons. Typically, these are roads, but other common examples are rivers, coastlines, or administrative areas. Built-up area polygons snap to an edge feature if one is generally aligned with the trend of the polygon edge and within the grouping distance away. Edge features can be lines or polygons. | Feature Layer |
minimum_building_count (Optional) |
The minimum number of buildings that must be collectively considered for representation by an output built-up area polygon. The default value is 4. The minimum building count must be greater than or equal to 0. | Long |
Code Sample
The following Python window script demonstrates how to use the DelineateBuiltUpAreas tool in immediate mode.
import arcpy
from arcpy import env
env.workspace = "C:/data"
env.referenceScale = "50000"
arcpy.DelineateBuiltUpAreas_cartography("bldg_pnt;bldg_poly",
"inBUA",
"RoadNetwork",
"100 Meters",
"125 Meters",
"BUApolypoint",
6)
Environments
- Reference Scale
The reference scale is only considered when the Grouping Distance or the Minimum Detail Size parameter value is entered in page units.