GPS tracking application

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Java

Am writing an application to track school going kids on their school journeys.
Please, I need a java code that creates polygons by buffering the route to have a width of about 100m.
How and where do I store the polygons' co-ordinates?

I also need another code that would take every update and check whether it lies within any of the polygons, if not, it should send an alert to the parent to show the deviation.

This checking should continue until the child reaches his destination.

I would also appreciate any other general advice on achieving my objective becasue I am new to programming.

NB. I have already done the part for sending the updates.