Some aspects of the use of fluxgate magnetometers (gradiometers) in geophysical prospection in archaeology

For more than half a century, air photographs made with hand held cameras have made major contributions to the discovery of sites in northern Europe. Most appear as discolorations in crops or soils. Photos taken over many years show different details which only a proper drawing on a large scale plan can reproduce. Two useful algorithms for the improvement of picture quality and for geometric correction, creating pseudo-vertical imagery are described. They can be used in standard mini computers with reasonable processing times and storage.