The estimation of the correlation coefficient between the adjacent misclosures in an extensive triangulation chain is firstly discussed.Then the effect of the centring errors on triangle misclosure is investigated,and the result is applied to the Jst order triangulation chain in China.The following conclusions are drawn:1) Under the general condition,for the practical purposes,the correlation coefficient ρ△
between adjacent misclosures can be estimated by using the formula rp
)/n,in which wi
is the triangle misclosure,m is the number of products of all adjacent triangle misclosures and n the number of wi
.2) The effect of the centring errors is usually very small and can be neglected.