The techniques adopted include magnetic method, gravity, transient electromagnetic method, frequency domain electromagnetic method, direct current method and seismic method. 其中包括磁法，重力，瞬变电磁法，频率域电磁法，直流电法和地震法等。
The watermark is embedded in the significant coefficient in the low frequency was found to be robust, but the watermarked image is easily visible distortion. 将浮水印藏在影像频率域中的低频带的重要系数，经研究可使浮水印较具强韧性来抵抗外部影像处理攻击，但也因此牺牲影像的品质。
