What changes between M41 and M42
The era switch changes more than a date label. M41 presents the pre-Rift strategic frame, with Cadia still serving as the fortress at the Cadian Gate. M42 introduces the Great Rift, updates affected dossiers, and reframes routes and regional labels around a divided Imperium.
The underlying chart remains stable so the comparison is readable. Keeping the same camera, segmenta, and landmarks lets the viewer see the rupture as a change in strategic context instead of jumping between two unrelated illustrations.
Cadia as the clearest comparison point
Cadia is the most immediate before-and-after record. In M41 it is a standing fortress world whose defenses help define the northern gate. In M42 the planet is destroyed, while its surviving soldiery, identity, and military tradition continue across the Imperium.
Opening Cadia on the interactive map places that dossier beside the same surrounding landmarks in either era. The comparison shows why a location can remain central to the setting even after its physical and administrative status changes completely.
Routes, labels, and world status
Routes should be read as navigational relationships rather than measured travel times. In M41 they provide a relatively coherent strategic web. In M42 the Rift makes some connections more dangerous, uncertain, or disproportionately valuable even when the drawn endpoints have not moved.
Individual dossiers carry the detailed changes. Some worlds are destroyed, isolated, besieged, renamed, or newly significant; others remain comparatively stable. The era toggle lets the large-scale visual change and the smaller record-level changes support one another.
How to make the comparison
Open the M41 chart, choose a landmark, and note its status and nearby routes. Then switch to M42 without changing the selected world. Repeating that process for Cadia, Vigilus, Baal, Terra, and the Eye of Terror produces a clearer comparison than trying to memorize two separate maps.
As with every Cartographia Imperialis layer, the result is a fan-made explanatory model. Dates, classifications, and broad relationships are presented for exploration, while exact coordinates and the geometry of the Rift remain intentionally approximate.