Decision makers from a variety of disciplines need to review large quantities of high-resolution visual information in real time. Data sets ranging from millions to billions of pixels or voxels are not uncommon and the number of simultaneous users many vary from one user to tens of users. A large area display of 2m by 4m, not an uncommon size, requires 95 million pixels to achieve near eye limiting resolution when viewed a 1m distance. The required size and resolution of these images far exceeds the ability of a single projection display. It is therefore necessary to devise techniques to seamlessly tile images from multiple projectors to meet this need. This paper discusses the difficulties in tiling multiple projectors, and the methods currently used to overcome them. Large area images exhibit geometric distortions caused by projector misalignment, imperfect lenses and folding mirrors and those from the displays themselves. The images, if uncorrected, generally have luminance and color variations both between, and within, each projector channel. Finally, the images must be tiled in such as way as to have smooth transitions between each of the projector channels.