Signal Quality Monitoring (SQM) proposes to detect anomalous Global Navigation Satellite System (GNSS) signal distortions primarily through the using the multi-correlator receivers. These receivers employ three or more correlator pairs per channel-each slaved to tracking pairs. Then the measurements from each channel are transformed to form detection metrics. However, previously such some metrics were only simple algebraic combinations of the measurements and did not describe truly the characteristics of the correlation peak. This paper introduced a metric which uses measurements of each channel to fit the quadratic model with least-squares method to monitor the GNSS signal.