The image is in slant range with a pixel spacing of 8.1 m in range by 5.3 m in azimuth, and oriented along the satellite track, with approximate viewing angles ranging from 24 to 31. The illumination direction is approximately from the west to the east. The ortho-image has a final planimetric positioning accuracy of 30 to 40 m. All geographical and geological features are thus more accurately located and plotted on the ortho-rectified image. Geophysical data sets Regional magnetic maps show the spatial distribution of geological units with different magnetic susceptibilities.
Sedimentary rocks have the lowest average susceptibility and basic igneous rocks, the highest.
In the CSZ, these differences in magnetic susceptibilities result in a highly variable field where the Precambrian rocks outcrop, and in a smooth field under the magnetically transparent Appalachian nappes. The magnetically contrasting areas correspond to variations in Precambrian lithologies and in Precambrian basement depth under the Appalachians. A convenient representation of the depth of the Precambrian basement is offered by the solutions of the Euler deconvolution. Therefore, where the Precambrian outcrops, Euler solutions are shallow, while under the St. Lawrence River, they deepen along with the Precambrian basement. Figure 3 .