Circular Error 90%.  Usually expressed as a distance in metres, the CE90 describes the positional error and accuracy of an aerial or satellite image.  It means, an identified control point in an image will fall within a circle having the radius of the stated CE90, 90% of the time, when compared to the true position on the Earth. The smaller the number, the better the positional accuracy will be. For example, our satellite imagery has a CE90 of 23m for the Quickbird satellite, but WorldView 3 and WorldView 4 have CE90 of only 3.5m.