This paper presents theoretical and practical implementation of the chipless RFID technology to measure the orientation of tags attached on a 2D surface. Analytical expressions are used to recover tag orientation from mono-static co-polarization measurements. Simulations are performed to validate the orientation estimation technique. Moreover, measurements in anechoic chamber and real environment are done to evaluate the performance of the proposed solution. Contrary to already implemented techniques, the one introduced in this paper is not sensitive to distance variations which is an advantage for practical applications. Our solution can estimate the orientation of a chipless tag with an error less than 5° in a range of 90° .