Overlay of Viking mounds and Mars Express images
The Viking images are from Horace Crater's presentation here. I overlaid these onto the new Mars Express images to see if the original mound locations were accurate compared to the new image. While the locations are approximately according to prediction, changing where on the mounds the lines are drawn from can make the angles change by a degree or more. So the hypothesis of their being constructed as an alien message depends on whether the positions the lines are drawn from are sufficiently unambiguous. A, B, and D have arguably significant points to measure from while E and G have some ambiguity. However using Z instead of E and A, B, and D there are quite precise relationships based on relatively unambiguous mound locations.
The triangle at Z is quite unusual considering Doctor Crater predicted a mound in this area to add to a triangular pattern.