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Old Boeing Driver
The RWY 18 TCH is 47.7 feet on the 3.20 degree PAPI Glide Slope. The RWY TDZ is 3 feet above the PAPI (630.6') which is the zero baseline for the drawing, i.e. 630 feet above MSL.
Below is a large scale high res portion of the graphic, showing the PAPI origin, with runway in blue which is 644 feet at threshold and a TCH height of 48 feet. So as drawn, the runway negative slope is increased by 3 feet over 1166, but that has no affect on the position of anything else.
The intercept of the PAPI centerline at IMTOY appears to be correct, but I haven't checked the coordinates, and the I-BXO LOC/DME may not be 'exact'.