Why is the error message “MapAnalyst is damaged and can’t be opened. You should move it to the Trash” displayed on Mac OS X? Open MapAnalyst. It should work this time …although you still get: “MapAnalyst is an application downloaded from the Internet. Are you sure you want to open it?” Click “Open” MapAnalyst assumes that the old map and the new reference map use the same projection. If they do not share a common projection, visualizations will be overly distorted. If the projection of the old map is known, the reference map should first be converted to this projection using a GIS, before the reference points are added. If the projection of the old map is not known (which is often the case), an approximation of the projection can possibly be deduced by an analysis of the distortion pattern. The projection does not play an important role and can often be ignored for maps at large and medium scale and/or for maps that are highly distorted. The recommended way is to compare each old map to a new reference map and to generate the visualizations in the coordinate system of the reference map (see for how to do this). You can then export the visualizations for each map and combine them in a GIS or a vector graphics software. This allows you to overlay the distortion visualizations of different maps. Yes, although the recommended way is the one outlined above involving a GIS. Nevertheless, you can load an old map instead of a modern reference map on the right side of the MapAnalyst window. Control points can then be added and visualizations can be computed as with a modern reference map. However, the scale value and all distances computed or displayed are completely meaningless in such cases. A distortion grid or displacement vectors computed in this way, however, might be useful: if the grid has regularly sized cells, and the vectors are very short, one map is likely a copy of the other map (or both maps are a copy of a third one). With the current version of MapAnalyst it is not possible to resample old maps to register them with reference maps. This feature is currently under development and will be released with one of the next updates. Scans of maps can be very large in terms of required memory. It is recommended that you down-sample your images to a maximum size of approximately 5000 by 5000 pixels. Large raster images might possibly slow down MapAnalyst, depending on the speed of your computer. The maximum possible size mainly depends on the amount of available memory. Source.