Hello Thiru,
People tracking needs in Oil&Gas vary from site to site depending on the biggest pain. In most sites the staff safety is the biggest pain point which relates to points #1 and #2 in your query.
1. The mustering application means automatic counting of people in mustering area. This is to be able to understand any possible loss os personnel in emergency situations.
2. People tracking can mean several things. For safety purposes the location of personnel can be tracked in order to be able to know that personnel is not entering unsafe areas. Also visitors of the site can be remotely monitored to ensure that they are in safe areas only and can be rescued if they get lost. Additionally people tracking can be utilized for improving the workflow by tracking the staff location. For example work orders can be dispatched to closest personnel.
3. Time and attendance application is for automating time keeping processes by tracking the location of personnel and counting the hours that they are present within workareas.
I hope this was of help to you. Please contact me in case you have further questions.
Regards, Arttu Huhtiniemi
http://www.ekahau.com