Helmert variance component estimation with non-negative constraint of covariance matrix
WANG Leyang, ZHAO Xiong, XU Wenbin, WANG Chisheng, FANG Nan, XIE Lei
Acta Geodaetica et Cartographica Sinica . 2022, (3): 351 -360 .  DOI: 10.11947/j.AGCS.2022.20200333