Abstract: For improving the digital map's quality,collocation method is a helpful tool to fit the systematic errors and weaken the effects of the stochastic errors.The main difference of the collocation applied in our situation is that the remained systematic errors resulted by the inaccurate covariance function will be fitted again and reduced from the estimated signals.In this way,the modified collocation can effectively resist the influences of systematic errors.An actual calculation and corresponding analysis show that the proposed method is effective in improving the quality of digital maps.