In the course of trying to find the significance of the Martha Tabram location, I noted that it comes within ten feet of the line between the Pinchin Street location and the steeple of Christ Church near Commercial and Fournier.
That got me to wondering whether it should be precisely on the line, and whether I had gotten the location right, so I decided to delve into the evidence more deeply. There is quite a debate over the precise location where her body was found, which is possibly intended as a hint of the significance of the precise location, and not to reach any conclusions. I concluded that she was found about halfway back, as I previously assumed just to save time. Some claim that she was found at the back of the building, but that doesn't make sense in light of some of the testimony from those who saw the body where it was left. A few of the witnesses believed Tabram's body to be someone sleeping on a stairway landing, which was supposedly customary (although I would have chosen the top floor, where there would be the minimum amount of traffic - but perhaps it was typical for all of them to occupied). I doubt it would be customary to sleep at the rear, because the rear was more open to the elements in a cold, wet city. Besides, if she had been found at the rear of the building, someone would have said so, but they all described the location as being part of the staircase. (The staircase apparently had a folded, or "switchback" configuration, and occupied the rear half of the building. The bottom of the staircase was apparently at the rear; at least this was the case in a nearby building which might have been based on the building in question, which was after all a "MODEL lodging house" - a prototype.)
The "best" evidence I saw that it was at the back, is a statement that the location was 12 feet from a certain apartment, which was assumed to mean from the apartment's entrance, although this was in the context of a discussion about the fact that nobody definitely heard the attack. In such a context, most people would refer to the minimum distance between their bed and the attack location, even if this distance were measured along an imaginary line running through walls. ("I was only X feet away, and I didn't hear a thing.") Another report used the term "right angle," indicating that there was a corner in the path from the rear of the apartment building to the attack site, which supports my position.
But this more detailed examination led to the discovery of a photo of the rear of the building (included as evidence in the aforementioned debate), and this led me to realize that I could directly pinpoint the location on the Ordinance Survey map excerpt which shows the outline of the building and the major surrounding streets. (The photo of the rear of the building also supports the general consensus on the configuration of the staircase, although it isn't definitive.) Before finding the photo, I wasn't able to put the map's outline of the building into perspective. I now realize that the section which extends behind the main building (which was added after the Ripper's rampage) ends at the stairwell, and that the stairwell is indicated in the OS map by the dark line across the main building, at the bottom end of the aforementioned addition, as indicated in the illustration above.
This allowed me to eliminate a step in the process which I previously used for determining the Tabram-coordinates. (I used a very detailed map to locate the stairwell in the area map, but this approach introduced some errors.) After pinpointing the stairwell directly on the area map, it was just a matter of taking careful measurements, determining ratios of distances between major streets, and transferring these ratios to Google Earth. The end result is the latest set of coordinates on my Jack the Ripper - significant locations map, which is about 7 feet further toward the south end of Gunthorpe than the previous coordinates. This put the coordinates a little closer to the line from Pinchin Street to the Christ Church steeple (in my Google Earth version), and when I zoom out, the Tabram location appears to be precisely on this line. In my opinion, it's close enough to conclude that it was intentional (the difference in the headings of Pinchin-Tabram vs. Pinchin-Christ Church is about 0.2 degree, and this could be due to measurement errors).