Endpoint device, central data collection point, and associated methods for collecting data over a communication network between endpoints and the central collection point. Actual measurements from a sensor are obtained by the endpoint device at a relatively fine time granularity. The endpoint device generates reports for receipt by a central data collection point. The reports include regular reports containing a portion of the actual measurements representing sensor measurements at a relatively coarse time granularity, and exception reports, containing information representing one or more of the actual measurements that differ in frequency or granularity of regular report measurements. Each of the exception reports is generated in response to a determination that at least one of the actual measurements differs from a predicted value for that at least one of the one or more actual measurements by an amount that exceeds a pre-established limit.