0 a soldier who guards a place, usually by standing at its entrance:
1 a soldier who guards a place and prevents those who are not allowed in from entering:
Discovering an unpredicted sentry(s) while moving along the created path can be easily accommodated.
At each free-space cell, the visibility risk cost to each sentry observing that cell is calculated.
The calculated visibility cost of that sentry at each affected cell is added to the previously stored cost.
The robot is exposed to the sentry at a far distance where it is more covert than the other shortcuts to the goal.
The new path is hidden from the known sentry but is still cautious from the unknown ones, as compared to the short path.
The approach has shown its capability of adapting with different levels of knowledge about both the operating environment and the sentries' locations.
This ability is important as it allows the robot to immediately maintain its covertness once it gets in the view field of an unpredicted sentry.
The estimated value at any location represents the risk level of being exposed to one or more sentries.
