Location is one of the most important contexts used in the applications in the pervasive computing environments . It helps the application do the right thing at the right place. On the other hand, location is the most difficult context to acquire and process. Location information cannot be obsing a single sensing system. It has to be abstracted to application-specific meanings before an application can understand it and utilize it. Since 802.11 networks are used widely, we use its RF signal strength to derive a client’s location. To facilitate the indoor location determination system development, we build a location toolkit, which includes several utility programs. The toolkit not only performs some common functionalities used in various location determination approaches, but also provides a straightforward visual interface to researchers and users. This paper presents our approach to developing an indoor location determination system based on the toolkit, and some research result...