This GoogleEarth view might be of interest
I added the terrain - it's exaggerated by 3, so the real slope is nowhere nearly as steep as this looks
This is from house 1 - someone around there would have the best place for a trigger, watching them all the way from the turn from river rd.
The "trigger house" would be mostly blocked by the buildings on the north side of chestnut ( Google dosen't show building heights )
The Taxi would be just about straight on - no good way to judge when to trigger at all, from position or timing.
I’m feeling sea-sick looking at that picture. :-) Interesting way to look at the triggerer issue. Great idea. I agree the taxi would be in a more difficult position to trigger the IED. However, there’s always the possibility of “luck” and that they had four chances to hit a vehicle.
You mention the alleged “trigger house” (to the North) would be blocked by buildings on the north. What about if they were on the roof? Seems like a lot of these houses have flat roofs that are easily accessible.
Logically, the general location of house 1 makes the most sense. What can also be noticed in looking at these pictures, is house 1 would likely have known about the placement of the IED in the first place. The IED was placed in the road and paved over to match the rest of the road. I’m assuming this would have taken some time and made a bit of noiese to tear up the original pavement and redo the pavement. Even at night, it would be hard to believe it wasn’t noticed.