Geodetic frameworks in most countries are still referenced to local horizontal geodetic datums. Therefore, GPS-determined geodetic networks have to be integrated to local (national) networks. In practice, this process is always achieved by a coordinate transformation. However, this common way has some difficulties. For avoiding these difficulties, an alternative way called DIDELOC is proposed in this study. The basis of this method is based on that the slope distances are datum free. Utilizing this property of slope distance, GPS baselines can be evaluated directly in local system by DIDELOC method. This method is successfully applied to the test data selected from the biggest hard coal basin of Turkey. The results show that the previous coordinates in the basin have experienced deformations caused by subsidence.