Binary format Trajectory format (binary) PCAzip The compression is made projecting the Cartesian snapshots collected along the trajectory into an orthogonal space defined by the most relevant eigenvectors obtained by diagonalization of the covariance matrix (PCA). In the compression/decompression process, part of the original information is lost, depending on the final number of eigenvectors chosen. However, with a reasonable choice of the set of eigenvectors the compression typically reduces the trajectory file to less than one tenth of their original size with very acceptable loss of information. Compression with PCAZip can only be applied to unsolvated structures. 1.22 PCAZip format is a binary compressed file to store atom coordinates based on Essential Dynamics (ED) and Principal Component Analysis (PCA).