This study outlines two novel techniques which can be used in the area of IP geolocation. First we introduce a detailed path-latency model to be able to determine the overall propagation delays along the network paths more accurately.This knowledge then leads to more precise geographic distance estimation between network routers and measurement nodes. In addition to the application of the detailed path-latency model,we describe a method which utilizes high-precision one-way delay measurements to further increase the accuracy of router geolocation techniques. The precise one-way delay values are used as a "path-constraint" to limit the overall geographic distance between the measurement nodes. The approach introduced in this paper can be used to localize all the network routers along the network path between the measurement nodes and can be combined with other existing geolocation techniques. The introduced techniques are validated in a wide range of experiments performed in the ETOMIC measurement infrastructure.