Hello. First off I am not pro nor trained for such interpretations and decoding. I am here specifically about the map. I plugged in some possible solutions and sat up a kind of "database" and mapping on Google Earth. I noticed one of the murders is missing from the pictures and I apologize for that. You should get the general gist.
I am happy to explain more for those who may be interested. Gotta go run errands.
The map accounts for the magnetic offset in the SF Bay area in 1969. It does not fluctuate much over the time period were concerned with. Then for inches along radians, I scaled my radians to the Mt. Diablo Map included in the letter. I used a clock for representation of radians. After all said and done, the only school that a radian runs directly through is Santa Rita Elementary School.
On the map, the radians align with some of the most prominant murders:
Chen Jo Bates
Donna Lass (Pines)
Edit** My apologies, I did not remember I have posted previously. I have been busy with school for a while. I am unsure if I can, or know how to delete them.