As you yourself pointed out on page 1, the Phillips 66 map has both a north-alignment error of approximately 5° and an actual scale of approximately 7.06 miles per inch, rather than the printed 6.4.

You also provided the following calculations:

«Bearing: 197 + 5 = 202°

Range: 38.38 / 7.06 = 5.436 inches.»

I think these figures are particularly interesting when compared with my Z32 interpretation.

My Z32 calculation:

– Magnetic bearing: 180°

– Historical easterly declination: approximately 17°

– True bearing: approximately 197°

– Distance: 6 inches × 6.4 miles per inch = 38.4 miles

Your corrected P66 calculation:

– Bearing from map north: 202°

– Distance: 5.436 inches × 7.06 miles per inch ≈ 38.38 miles

Once the map’s north-alignment error is accounted for, both calculations give essentially the same geographic bearing and distance.

This also raises an interesting question about your 12-radial diagram.

If the vertical axis of the P66 map is approximately 5° west of true north, then placing magnetic north 17° clockwise from that axis would not account for the map’s rotation.

Using the correction you identified, magnetic north would instead be approximately 22° clockwise from the map’s vertical, placing magnetic south at approximately 202°.

That is almost exactly the bearing you calculated for Neary Quarry.

In other words, your own corrected measurements appear to converge remarkably closely with the direction and distance derived from my Z32 interpretation.

I think that is a rather interesting point of agreement between our two approaches.

—

Turning to the three points in your latest post:

1. Compass and navigation

I agree that plotting a location on a map is not the same as physically navigating to it.

However, establishing magnetic north still requires a reference. You can use a compass, or calculate it from true north using the historical magnetic declination.

And Zodiac did write, “you have until next Fall to dig it up.” So while the initial task may be to establish a location on a map, someone would eventually have to reach that location.

2. The 12 radials and magnetic declination

Your explanation that Zodiac may have selected magnetic north to bring an intended destination onto one of the 12 radials is certainly possible.

However, applying the approximately 5° map-alignment correction you identified to your radial diagram places magnetic south at approximately 202° from the map’s vertical, matching the bearing you calculated for Neary Quarry on page 1.

3. The length of Z32 and fractional values

You suggest that Z32 may be too short to accommodate fractional values in both the bearing and distance.

But Zodiac chose the length of the cipher himself. If more symbols were required, he could have made it longer.

In my interpretation, the two SIX values already provide the necessary information without fractions: one establishes the directional position, and the other supplies the map distance.

—

Regarding your three-step sequence

In my approach, the map is part of the key, not simply the final plotting surface.

That is the fundamental difference between our interpretations.

You begin with:

1. Solve the cipher.

But in my interpretation, solving Z32 and performing the map operation are not two separate stages. They are part of the same process.

The Phillips 66 map supplies information needed to interpret the cipher itself, including the directional reference and the printed scale.

So I am not suggesting that your three steps fail to work together. I am suggesting that your first step assumes the cipher can be solved independently of the map.

My interpretation does not make that assumption.

There is nothing inherently wrong with your three-step interpretation. It is a perfectly reasonable approach.

But I don’t see why it should be regarded as the only obvious interpretation.

My approach does not depend on GPS or modern mapping technology. It uses a paper map, magnetic north, radians, and the printed map scale — all available in 1970.

The distinction is that I treat the map as part of the cipher’s key, rather than assuming that the final location must be established by physically measuring inches on that particular sheet of paper.

Your own findings concerning the P66 map’s orientation and scale are relevant here. They show why a distance derived from the printed scale need not correspond to the same physical measurement on the map.

So the reason I am considering another interpretation is not a modern mapping bias. It is that the instructions allow us to investigate how the cipher and map work together, without assuming in advance that your three-step sequence is the only possible operation.

Posted by: @northkey

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2. The 12 radials and magnetic declination

Your explanation that Zodiac may have selected magnetic north to bring an intended destination onto one of the 12 radials is certainly possible.

However, applying the approximately 5° map-alignment correction you identified to your radial diagram places magnetic south at approximately 202° from the map’s vertical, matching the bearing you calculated for Neary Quarry on page 1.

This reasoning evidences a major conflation between your application to the map and to the real world of certain concepts. Actual magnetic north at the time certainly does move actual magnetic south around to 202° relative to north on the Phillips 66. But we are using the map. We are not interested in the real-world correspondences. We are interested in where we get to if we rotate map north round by 17°. Yes, the north direction marked on the map is out by 5°, but it is the map we have been given and, as you acknowledge, no one in 1970 was analysing the Phillips 66 to see if it were properly aligned and scaled. Consequently, on the map, magnetic south is (albeit erroneously) at 197°.

The rest of what you’re adding prior to this does confuse me, however. You seem to be merely applying the corrections required from the analysis to reach the real-word coordinates from those on the map and then expressing surprise when they match. ???

Posted by: @northkey

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There is nothing inherently wrong with your three-step interpretation.

It is categorically not an ‘interpretation’. That is the point.

Here’s a piece of paper with some stuff on it. Here’s a bearing and a length in inches. Go get a protractor and an inch ruler. Where does it get you?

It is a gross error to suppose that your alternate method here sits in any degree at the same level of plausibility.

Posted by: @northkey

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So I am not suggesting that your three steps fail to work together. I am suggesting that your first step assumes the cipher can be solved independently of the map.

 

My interpretation does not make that assumption.

On the contrary, the straight-forward method makes no assumptions beyond the mere fact that we’ve been given a map so we work on the map, which is wholly reasonable and obvious and demands no formal statement. Your method, in contrast makes the unfounded assumption that, aside from the hand additions, we should confine ourselves only to considering the erroneous scale value and then set the map aside.

Where were we instructed to do that?

Posted by: @northkey

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My interpretation uses the scale as it was printed on the map Zodiac supplied. Whether that printed scale was geographically accurate is a separate question. A modern demonstration that the map itself was inaccurate cannot retrospectively alter the scale that a solver in 1970 was given and would have had to work with.

The solver in 1970 was given a physical map and a distance in inches. There is then no need to give consideration to any scale whatsoever, correct or otherwise. The map could be as inaccurate as you like, it would change nothing. This is the simplicity of the method you seek some alternative to. What I have yet to fully understand is why. To my present understanding it merely smacks of post hoc retro-fitting to a favoured result. How might you help me to see it otherwise?

I agree that we were given a map, and that working with that map is the obvious starting point.

But I think you are overlooking how much of the Phillips 66 map my method actually uses.

Mount Diablo establishes the geographic origin. Zodiac’s 0–3–6–9 diagram provides the directional framework, with 0 set to magnetic north. The printed scale converts the decoded six inches into approximately 38.4 miles.

The map and cipher therefore work together. I am not assuming that the cipher can be solved independently of the map, nor am I simply extracting the scale and discarding everything else.

Where our methods differ is in what happens after the direction and distance have been established.

Even if you measure six physical inches directly on the Phillips 66 map, its printed scale still represents approximately 38.4 miles.

Once that distance has been established, it can be transferred to a more detailed map using that map’s own scale, while preserving the correct geographic bearing and Mount Diablo as the origin.

The reason for consulting a more detailed map arises from the result of the Phillips 66 operation itself.

Once we have a direction and a distance, the practical question becomes: what is actually located at the calculated position?

Would investigators in 1970 necessarily have driven out with the Phillips 66 gas-station map alone, or would they first have consulted more detailed maps to determine what was present in that area?

That is not an assumption required to solve the cipher. It is a natural investigative step following the operation.

And this is where the distinction between the map’s printed north and the actual magnetic direction becomes important.

If we measure directly on the Phillips 66 map using its erroneous orientation, we may obtain a different geographic endpoint.

But my original operation uses a compass-based magnetic north reference. Position 6 gives 180° magnetic. Applying the historical declination of approximately 16°53′ east gives a true geographic bearing of approximately 196°53′.

Together with the nominal distance of 38.4 miles from Mount Diablo, that produces approximately the same geographic endpoint near the historical Neary/Gravel Pit area when plotted on a correctly oriented map.

The endpoint does not change simply because a different map scale is used.

There is also an important point about the chronology.

When I developed and posted my Z32 interpretation, I was not aware of the orientation error in the Phillips 66 map.

I only became aware of it after you pointed it out, following my original post.

And discovering that error did not cause me to change the Z32 operation or its calculated result.

The decoded values remained the same. The magnetic bearing remained 180°, the corresponding true bearing remained approximately 196°53′, and the distance remained approximately 38.4 miles.

What I corrected was my explanation of how the Phillips 66 map is used, particularly the distinction between its printed north direction and magnetic north established independently using a compass.

I did not introduce a new bearing, alter the distance, or move the proposed endpoint in response to your observation.

Your observation helped clarify the role of the original map in my method. It did not require me to change the underlying calculation.

So, to answer your question directly: no, Zodiac did not explicitly instruct us to consult a more detailed map.

But neither did he instruct us to use the original Phillips 66 map as the exclusive geographic plotting surface throughout the entire operation.

Treating the Phillips 66 map as the only permissible plotting surface is itself an assumption. It may be a reasonable one, but it is not an explicit instruction from Zodiac.

That is precisely why I regard it as an interpretation rather than an established requirement of the cipher.

The original map is essential to establishing the operation. A more detailed map allows us to investigate the resulting geographic location.

Those two uses of maps are entirely compatible.

Posted by: @northkey

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So, to answer your question directly: no, Zodiac did not explicitly instruct us to consult a more detailed map.

The question was not whether The Zodiac had instructed us to use another map or not. It was where we had been instructed only to give consideration to the scale on the map we were given and then perform calculations to determine where that would reference on the assumption that the map scale were correct. Because the two methods produce different results, as we know.

The direct and obvious one requires no consideration of any scale whatsoever. The operation is wholly unchanged if we were to have found that the Phillips 66 had no scale marked on it at all, correct or incorrect. And we are not directed to the scale. Thus the application of any method that does use the scale at all, in preference over the simple act of measuring inches, as we were given, requires justification.

The two methods produce different results. WHY are we to prefer the abstract one that demands we pull back from the map as a measurable artefact and perform operations we weren’t explicitly directed to carry out?

Let’s focus back on this for a second.

Posted by: @northkey

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Treating the Phillips 66 map as the only permissible plotting surface is itself an assumption. It may be a reasonable one, but it is not an explicit instruction from Zodiac.

We were explicitly and incontrovertibly given it. We were directed, along with the code, to use “The Map.” There is no ‘assuming’ here.

The Map.

… as a Map.

Point to a place or area on the Map. Then you can put the map down and go there by whatever means you like.

Posted by: @northkey

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Even if you measure six physical inches directly on the Phillips 66 map, its printed scale still represents approximately 38.4 miles.

Six inches on the Phillips 66 map represents 42.24 miles on the ground. You keep fudging the difference issue as if it isn’t there. It doesn’t matter what the printed scale says.

I can go a little further with this if an answer is forthcoming to the question posed, otherwise I think everything has been covered.

Posted by: @shaqmeister

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Six inches on the Phillips 66 map represents 42.24 miles on the ground. You keep fudging the difference issue as if it isn’t there. It doesn’t matter what the printed scale says.

And more to the point, as a final note, it doesn’t matter what the distance on the map corresponds to in miles on the ground, because we’re not interested in “on the ground.”

The Zodiac merely measured the length, in inches, of a straight line between two points on the map, and our job is simply to reconstruct this length from the cipher, in inches, and read off, from the map, where it ends.

Thank you for taking the time to explain your position. I appreciate the discussion, even though we clearly disagree on how Zodiac’s instructions should be interpreted.

You say that we are not interested in the distance “on the ground.”

But Zodiac explicitly wrote: “You have untill next Fall to dig it up.”

That IS an instruction from Zodiac himself. It concerns a physical location in the real world, not merely a point on a paper map. Whether anything was actually buried is a separate question.

You also state that Zodiac simply measured a straight line between two points on the Phillips 66 map. But that is YOUR interpretation of how he constructed the puzzle, not something Zodiac actually told us.

I think there is a misunderstanding about when and why we convert inches into miles.

The conversion is not part of the cipher-solving operation. We first derive the proposed instruction from Z32: Mount Diablo, the six direction relative to magnetic north, and six inches.

Only after that do we use the printed scale to convert those six inches into 38.4 miles, so that we can investigate where the resulting bearing and distance lead in the real world.

That is a geographical check of the proposed solution, not an additional step required to derive it from the cipher.

You also wrote:

“We were explicitly and incontrovertibly given it. We were directed, along with the code, to use ‘The Map.’ There is no ‘assuming’ here.

The Map.

… as a Map.

Point to a place or area on the Map. Then you can put the map down and go there by whatever means you like.”

But that is exactly what we are doing. We use the Phillips 66 map, its printed scale, and Zodiac’s magnetic north instruction to establish a geographical direction and distance. We then put that map down and transfer the bearing and distance to a more detailed map to investigate where they lead.

Our disagreement is not about whether to use “The Map.” It is about whether using that map necessarily means physically measuring six inches on the paper, rather than using the scale printed on it. You are asking why we introduce the scale into the cipher operation. We don’t. We use it afterwards to investigate the geographical endpoint.

And finally, your figure of 42.24 miles is based on a retrospectively calculated scale of 7.04 miles per inch. That is not the scale printed on the Phillips 66 map. The map states approximately 6.4 miles per inch, giving 38.4 miles for six inches.

You previously referred to “the cognitive bias inherent in the modern GPS mapping era.”

Yet your conclusion that the Phillips 66 map has an effective scale of 7.04 miles per inch must itself rely on geographical information beyond the map Zodiac provided. The printed scale says approximately 6.4 miles per inch.

So while you insist that we must work with “The Map” Zodiac gave us, you are also introducing external geographical information to correct that very map.

That is the inconsistency I am questioning. Why should information from outside the Phillips 66 map be acceptable when correcting its scale, but not when investigating the geographical endpoint of our proposed solution?

We are not ignoring the discrepancy. We are questioning why a retrospectively calculated correction should override the scale actually printed on the map Zodiac supplied.

And since you say that it doesn’t matter what the printed scale says, why must the six inches be measured physically on the Phillips 66 map? Where did Zodiac instruct us to disregard the printed scale but treat the physical dimensions of that particular map as definitive? And what makes your interpretation the only valid way to use the map Zodiac provided? And if the scale does not matter, why should converting inches into miles be a problem?

If we are to solve the puzzle using the information Zodiac provided in 1970, we must start with what the map actually tells us — not what we later discovered it should have told us.

Posted by: @northkey

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You say that we are not interested in the distance “on the ground.”

But Zodiac explicitly wrote: “You have untill next Fall to dig it up.”

We are not interested in any “distance on the ground.” You dropped distance out of the quotes. Once we’ve identified the place or area on the map, sure, we’re gonna go there.

How far the bomb location is from Mount Diablo in statute miles is not of any relevance to the problem and its solution whatsoever. NONE! I’m sure LE are not going to be driving there having gone to the summit first.

As to your other points here, I’m simply not seeing the same prowess and acumen that you appeared to show in your last thread. Just forget scale. Forget how accurate the map is and whether The Zodiac knew that even. Forget statute miles, the distance from Mount Diablo in miles is an utter irrelevance.

We have a map, and we have map coordinates. IN INCHES.

And I know this is going to sound horrendously arrogant, @Northkey, and I do apologise, but I am not merely presenting an alternative and competing interpretation here, I am correcting the errors inherent in yours. You have an epiphany awaiting you. 🤔

Posted by: @northkey

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Only after that do we use the printed scale to convert those six inches into 38.4 miles, so that we can investigate where the resulting bearing and distance lead in the real world.

The bearing and distance are given to us, the latter in inches.They point to a place we can identify on the map. In the real world, we go there.

Maps have places and roads and towns marked on them. We can point to them … on the Map. Please don’t try and convert the London Underground map into bearing and distance. You will become hopelessly lost. Just get on the right line and get off when your station is called.

Posted by: @northkey

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Yet your conclusion that the Phillips 66 map has an effective scale of 7.04 miles per inch must itself rely on geographical information beyond the map Zodiac provided. The printed scale says approximately 6.4 miles per inch.

My explanation assumes nothing whatsoever about the scale. Absolutely NOTHING! No conversion of any kind is required at any point!! It can be three beetle wings to the length of a Canadian freight train, the scale is irrelevant.

Given inches, use inches.