For example, you said he didn’t use RADIANS in the plaintext.  This goes against his explicit instruction/hint.  Did he misuse the word?  That is another story.  Clock hours hint would be radial lines.

In summary, then …

A map does not have to be accurate to function as a map. The London tube station map provides the perfect illustration of this fact. What is consistent about the way that we use any map whatsoever is the following: whatever it is that we are identifying on the map—any map, accurate or otherwise—is precisely what we are intending to reference on the ground also.

And we can identify features on a map in a multitude of ways. We could, for example, merely point to a specific feature and have it understood by the person looking at it with us that this is the place that we are interested in. Alternatively, we might stick each of two pins in distant points on the map, and from each extend a pencil on a string, each of a given length, and advise our friend that the place I want to draw attention to is at that point where the two arcs drawn by said two pencils cross. And if these two arcs cross at, say, Euston station, then Euston station is precisely the place in am interested in.

Likewise, we may set down a single pin in a specific location, such as where the summit of Mount Diablo is drawn on the Phillips 66 map, and we might further draw out our string again to a specific length. We can then draw a full arc on the map and, this time, indicate my specific point of interest by having you draw a straight line out from Mount Diablo at a given angle to straight-up-the-page.

However we were to do this, the point is this… It is not the method of construction, nor the ‘coordinates’, nor anything else that, of themselves, single out my place of interest. It is that, using this method, these coordinates, on this map… this is what they point to. And if that point on the map thus identified corresponds, on the map, to the intersection of Tuolumne and Valle Vista in Vallejo, CA then, on the ground, it must correspond to this same intersection also.

What we don’t get to do is take the coordinates of this intersection as they relate to our imprecise map and apply them, without correction, to our modern Google map and then claim that they are actually pointing somewhere else.

This is not how maps work. 

What I identify on my map is what I want you to identify on the ground. It’s the feature that is of importance, not how we located it on the map, what coordinates we might have used.

So, if you are still insistent on using Google Maps to help you solve the Z32 cipher, you at the very least have to do the following. You have to first analyse the Phillips 66 Map and determine precisely, and in what manner, it relates to the representation of the same area on your Google Map. You will find that the Phillips 66 Map is rotated very slightly, so that true north and map north are out by about 1 to 2 degrees. You will also find that the stated scale of 6.4 miles to the inch is actually inaccurate, and you would need then to use a corrected conversion factor, once determined, in order to translate map inches into miles on Google. Then, having done this, you will know how to correct for the coarse errors of the Phillips 66 to reach your equivalent coordinates on Google Maps, only …

Only you will know when you have satisfactorily introduced all the required corrections precisely when the raw measurement on the Map and your converted coordinates on Google Maps converge in identifying one and the same place.

Posted by: @shaqmeister

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So, if you are still insistent on using Google Maps to help you solve the Z32 cipher, you at the very least have to do the following. You have to first analyse the Phillips 66 Map and determine precisely, and in what manner, it relates to the representation of the same area on your Google Map.

A preliminary analysis (I won’t go into the details here) would have the map north direction on the Phillips 66 map—that is, the direction corresponding to straight up the map page—to be somewhere close to 5° off, counterclockwise, from true north. Likewise, the overall scale of the map, rather than showing 6.4 miles to the inch, is somewhere closer to 7.04 miles to the inch.

Posted by: @shaqmeister

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A preliminary analysis (I won’t go into the details here)…

See Plotting your Z32 Solution using Google Maps (if you must) for the detailed analysis.

Posted by: @coder1987

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For example, you said he didn’t use RADIANS in the plaintext.  This goes against his explicit instruction/hint.  Did he misuse the word?  That is another story.  Clock hours hint would be radial lines.

The Zodiac’s misuse of this word, which I wholly agree with, is such that it is no longer a unit of measurement—as are ‘hours’ or ‘degrees’—but simply a descriptor—as ‘radial lines’.

We might then still see the word ‘RADIAN’ in the plaintext, as in ‘THIRDRADIAN’ or ‘RADIANTHREE’, but should not expect to encounter its plural form, e.g. ‘THREERADIANS’. 

It is for this reason that we likely have the subtle phrase “concerns Radians” in the postscript, rather than any indication that, like inches, we should be thinking of ‘[#]RADIANS’ (plural).

Some final, reflective thoughts.

It’s 1970, and we’ve just been handed a section of a gas station road map and a cipher. It is an alternative universe we inhabit and, in this universe, the Harden’s were likewise able to solve the Z32 just as easily as they had the Z408. We have, therefore, a coordinate pair which, without needing to be specific here, “concerns Radians and #inches along the Radians.” Basically, we have the Phillips 66 map of the San Francisco Bay area, together with something constituting (in form) a bearing (from Magnetic North at Mount Diablo) and a range (in inches). What, then, are we to do with these?

It’s 1970, and we have a map and a distance in inches. What options do we then have as to where we are to apply this distance in inches? We certainly have inch rulers in 1970, and we do have a map. We could apply this distance in inches there, couldn’t we?

More importantly than this, however, is the following question: Is there, at all, anywhere else that we could apply an inch distance to find a place?

The answer to this question, I feel compelled to argue, is categorically no.

In 1970, the only even vaguely conceivable alternative to simply laying out the inch distance on the Phillips 66 Map is to lay it out on some other Map? Only, the Zodiac has not given, nor identified for us, any other map. And, having not done so, we could have no knowledge of what the scale of that other map is and where our inch distance would take us.

Even if we had had some ‘alternative’ map identified for us, we would then be compelled to undertake conversions of scale and adjustments for the errors of the Phillips that would add nothing to the actual complexity of the initial obfuscation through the cipher, especially when he could have given us that actual map instead of the Phillips, and would only be serving to waste his time as much as ours. And, even then, the result that we would achieve on this other map would have to match the same location that we would get from simply laying out the inch distance on the Phillips 66, and so it wouldn’t be leading us to any information we wouldn’t have already.

In short, the only strategy that is open to us is to heed the North direction on the Map, mark around a positive angle from there at Diablo corresponding to our personal preference as to what the Bay Area magnetic declination was in 1970 and then plot out the coordinates that the Harden’s (in this alternative universe) had provided for us. And then, in the most simplest of fashions, where it lands us is where it lands us.