In this paper we have proposed an algorithmic scheme for detecting, determining and monitoring the shape and boundary of an expanding hole in sensor networks. Our algorithms are designed in a distributed manner to help their surviving of the expanding of a hole and reporting regularly about the hole status.

We have also conducted the simulation experiments to evaluate the effects of the important thresholds (DNT, NTT, RPT) on the performance metrics of our algorithms.
The simulation results show that the performance metrics are strongly dependant on how suitably we choose the mentioned threshold parameter for a given network setting. Obviously, the thresholds should be selected in accordance with the characteristics of the network, especially the expansion speed of the considered hole.

It is obvious that although we have done some complicated experiments which require some heavy simulation work there still remain many unanswered interesting questions and important technical issues. There are $3$ important threshold parameters yet there still are other important parameters such as the grid square size or the speed of the hole expansion; thus, it seem challenging to mix the selection of these to a good effect. Most challenging, perhaps is the concern that the hole expansion speed is normally unforeseeable and hence, we face a big trouble: a parameter set that is nicely suitable to a fast expansion setting can perform very poorly in a slow expansion setting. Thus, it is natural to think of further work with improved algorithms where the important parameters such as the grid size can be adjusted dynamically during the execution process. 