Clarification: P66 may be the key, not the plotting surface
When I first posted my Z32 candidate, I assumed that SIX INCHES had to be measured physically on the Phillips 66 map itself.
After seeing Shaq’s direct plotting, I realised two things: the supplied P66 section is much smaller than I had assumed — about 8″ × 6¾” (20.3 × 17.1 cm) — and my SIX/SIX construction does not physically land at Neary when six literal inches are measured on that sheet.
I initially thought this was a serious problem with the plaintext.
I now think the problem may instead be the assumption that P66 has to be the final plotting surface.
Zodiac wrote:
“The map coupled with this code will tell you where the bomb is set.”
He did not say that the destination had to be physically plotted on that particular sheet.
My current interpretation is therefore:
P66 supplies the system. Z32 supplies the values.
P66 gives us:
- Mount Diablo as the origin
- the 0–3–6–9 dial
- “0 is to be set to Mag. N.”
- approximately 1 inch = 6.4 miles
Within my restricted plaintext grammar,
AT [direction] [distance] INCHES FROM MOUNT DIABLO [destination]
the Z32 repeat structure selects SIX / SIX before any geography is examined.
Among the four values actually printed on the dial — ZERO, THREE, SIX and NINE — SIX is the only three-letter direction that fits the remaining space, while the repeated-symbol constraints also select SIX as the distance word.
This gives:
AT SIX SIX INCHES FROM MOUNT DIABLO ??T
So SIX/SIX is not being chosen because Neary happens to lie there. The values come first.
The first SIX selects position 6 on the dial.
If:
0 = Magnetic North
then:
6 = Magnetic South
or, mathematically, half a revolution / π radians.
I now think this should be understood as a real-world magnetic reference, established by a magnetic compass in the original 1970 method, rather than by treating the graphical north of the P66 road map as precision geometry.
This distinction matters. If the road map itself is slightly misaligned and we use its graphical north as exact True North, that error is carried into the resulting bearing.
A compass does not depend on the road graphics. It establishes the real-world magnetic direction independently.
The second SIX gives:
SIX INCHES
If the destination were being plotted directly on P66, no conversion would be necessary. We could simply measure six physical inches.
But if P66 is instead the decoding key, then we need a map-independent geographic distance:
6 × 6.4 ≈ 38.4 miles
So the combined instruction becomes:
FROM MOUNT DIABLO
MAGNETIC SOUTH
APPROXIMATELY 38.4 MILES
That vector can then be transferred to a more suitable map using that map’s own scale.
The second map does not need to have the same scale as P66. That is exactly why the conversion from inches to miles matters.
The workflow therefore becomes:
P66 + Z32 → geographic vector → second map → location
rather than:
Z32 → ruler/protractor directly on P66 → location
Only after fixing that vector do I check the geography.
Neary Quarry is approximately 38.4 miles from Mount Diablo and lies very close to the corresponding magnetic-south direction.
That is why the remaining:
??T → PIT
is interesting to me.
The important order is:
Z32 structure → SIX/SIX
then:
P66 → Magnetic South / 38.4 miles
and only then:
geography → Neary Quarry
So the main correction to my earlier posts is simple:
I no longer think SIX INCHES should be physically plotted on P66.
I originally assumed P66 had to perform two jobs: decode the instruction and serve as the final plotting map.
I now think it may only need to perform the first.
P66 may be the key that converts Z32 into a real-world direction and distance.
I am not claiming this proves the plaintext. The largest remaining plaintext assumption is still FROM MOUNT DIABLO, because the map itself already supplies Mount Diablo, and PIT is not completely cipher-forced.
But the proposed mechanism is now quite simple:
P66 is the key.
Z32 selects SIX/SIX.
The magnetic reference gives the direction.
The printed scale gives the distance.
A second map gives the location.