The EM(BR)xxx series differential barometer/altimeter (patent pending)environmental monitor is a lower accuracy version of the DB(BR)xxx but provides additional metrics of humidity and gas. This product  integrates the EMOxxx module in a ruggedized unit with built-in power source and Bluetooth (rover only) capabilities.  Optional GPS tracking is available in the EM(BR)Gxxx variants.   
 
The unit provides atmospheric pressures and derived elevations at a rover using corrections transmitted from a stationary base.   In traditional systems elevations are calculated based on pressure readings for a stand-alone unit and are subject to the errors inherent with environmental changes in pressure.  Some applications of this versatile engine include indoor elevations, building pressurization monitoring, multi-node telemetry networks and UAV altitude references.  The EMDxxx is a special purpose base Forward Rate of Growth (FROG) sensor (patent pending).