Quality of the watermarked data is an important metric for measuring the invisibility of the watermark and the validity of the marked data. Some energy based metrics

e.g. peak signal to noise ratio(PSNR)

have some limitations while applied to vector map watermarking systems. This paper considered this issue in the aspect of map shape. The idea of time series clustering and shape similarity matching techniques has been used and the watermarked-map quality measurement based on distance metric is presented. The proposed algorithm extracts 1D feature functions from 2D vector maps and evaluates the quality of the watermarked data by measuring the shape difference between two feature functions before and after watermark embedding. Experiment results indicate that the proposed metric fits the characteristic of vector map data better and

furthermore

it can achieve more reasonable measuring results than previous methods.