Today, radar systems are used in a variety of applications including remote sensing. One of the most important challenges is to determine the position and the displacement vector of targets with high accuracy. For this purpose, the sensors installed on the ground platforms are used. In this paper, a method is presented that determines the absolute and relative position of the targets and also estimates the displacement of the targets in three dimensions. An FMCW mm-wave ground-based MIMO radar that has two transmitter antennas and four-receiver antennas are simulated. The sensor is designed to move on a two-dimensional plane and received the echo signals which are propagated by transmitters. Using the phase information of the signals captured by receivers antennas in different positions of the sensor, the arrival angle of the signal reflected from the target to the receiver antenna is determined. Then using the least square adjustment equations, the absolute location of the target is determined in the 3D space. Two scenarios were performed to evaluate the proposed model. The first test showed that the RMSE of the absolute position determination is less than 3 mm. in the second scenario, the determination of the displacement vector of the targets is examined. The result shows that the RMSE of the estimated displacement vector in three dimensions is less than 0.1 mm. It was also shown that the proposed method has no limitation in determining the relative displacement with different sizes. The presented model has the ability of the large displacement estimation without using phase unwrapping algorithms.