Traditionally

buffer zones of point features are circles with multiple radii. This means that same effect is used within the same radius around a point feature. In fact

a region affected by a point feature is possibly a sector buffer zone

not a circle

due to affecting factors such as wind direction

mountain range

ocean

transportation and so forth. The objective of this study is to enrich the theory and method of buffer zoning in GIS spatial analysis so as to meet the need of analyzing sector buffer zone for point features. Sector buffer zones are discussed with respect to its definition

data structure

fundamentals

algorithms and possible applications. To analyze point features with sector buffer zones

we developed a module using Visual Basic.NET and ArcObjects within ARC\INFO 9.3. After creating a polygon layer

iteratively

the layer field values are read iteratively

and the coordinates of the arc endpoints and chord length are calculated. Then the arc and the two edges of the sector were added

respectively

into the instance defined by an ISegmentCollection which then is assigned to a feature shape. If necessary

the overlaing polygons are handled. Sector buffer wizards with five forms were developed to select different methods and parameters conveniently according to different demands. The wizard provides more choices including the selection of features

radii

central angles

and initial angles. This module can append to ArcMap or ArcToolbox to use it conveniently

automatically

and dynamically. To validate the practicability

applicability

and effectiveness of sector buffer zones

two examples are used for demonstration. One uses sector buffer zones of video cameras distributed on the crossing roads in Kaifeng City

Henan Province

China. The other example analyzes the relationship between rural household income and rural migrant workers in Huangzhuang Village in Zhenping County

Henan Province

China

using the sector buffer zone method. A circle buffer zone is a special case of a sector buffer zone when the central angle of the sector is equal to 360°. Sector buffer zone is an expansion of the circle buffer zone. Results indicate that sector buffer zone

compared to circle buffer zone

has more information and regularities. It is very convenient for the analysis of point feature to reach more credible conclusions and to make decisions for administrators more accurately. In the future

more methods for drawing buffer zones with respect to point features

polyline features

and polygon features will be studied to make buffer system more robust and more perfect so as to meet the need of spatial analysis.