Provided is a system for measuring an etch stage of an etch process involving one or more layers in a substrate, the etch stage measurement system configured to meet two or more etch stage measurement objectives. The system includes an etch process tool, the etch process tool having an etch chamber, a controller, and process parameters. The etch process tool is coupled to two or more optical metrology devices and at least one etch sensor device measuring an etch process parameter with high correlation to the etch stage. The processor is coupled to the etch process tool and is configured to extract an etch measurement value using a correlation of etch stage measurements to actual etch stage data and etch stage measurement obtained from the two or more metrology devices and the at least one etch process sensor device.