含水印数据的质量评价是衡量水印嵌入隐蔽性和数据可用性的重要指标。峰值信噪比（PSNR）等基于能量的度量指标在应用于矢量地图水印系统时具有一定的局限性。从形状的角度考虑了矢量地图水印的数据质量评价问题，借鉴时间序列聚类和形状相似性匹配的思想，提出了基于距离度量的水印地图数据评价指标。算法从2维矢量地图中提取1维特征函数，通过度量水印嵌入前后特征函数的形状差异来评价含水印地图的数据质量。实验结果证明，本文提出的度量方法更符合矢量数据的特点，能够得到比现有方法更准确的度量结果。

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.