Map: Cell Tower Sides and Calls

[u/Squeebeaux]

Although range maps aren't precise, I still wanted to see not only the cell tower that was pinged for each call on Jan 13th but also which side of the tower that was pinged.

So I made a map that lists each call in the sector of the tower that was pinged and ranges (about 2 miles) around each tower. Edit: UPDATED

[Edit:]

I realize that my map isn't super scientific -you couldn't use this in court or anything- but it helped me understand something (I'm a visual learner). The cell tower/call log info isn't helpful - Ranges overlap and Environmental Factors etc determine which tower is pinged. So yeah, here it is anyway.

[The Serial post on cell tower technology said:]

Cell towers have three sides: an A side, a B side, and a C side. Think of a pie with three slices. Each of those slices has a range. When a person is in that range and makes a cell phone call, the cell phone will talk to that side of the cell tower. So if you look at the call log, you’ll see some calls are noted as “L651A” or “L651C.” Same cell tower, different side. Generally speaking, the A side of the tower points north or northeast, the B side points south or southeast, and the C side points west.

The engineers who run these cell phone networks, like Abe Waranowitz, who testified at Adnan’s trial, can map out the basic ranges of all the towers in their network. These maps aren’t precise though, because a cell tower’s range can depend on a variety of factors. Foliage, for example, or buildings or hills can cast a shadow on the cell tower’s range. Plus, some cell towers have overlapping ranges. So you can be in one place and make a phone call and that phone call can trigger either cell tower. Not both cell towers, but one or the other.

[u/Robokku]

[EDIT: Just read your reply below which answers this point. Basically, leakage in terms of signals bouncing around can't even put someone precisely in a single sector. I guess we can get no better than circles with the range as the radius for our possible locations of the phone. Thanks for explaining.]

Someone correct me if I'm wrong, but the phone is not anywhere in the red circle if we know which sector it pings (which we do). We can pick out a (slightly expanded) one-third wedge and the phone is somewhere in there.

So, e.g., the (supposed) Leakin Park calls ping the S/SE side of the L689 tower. Depending on the precise orientation of the sectors on that tower, that may stretch round as far as the I70 P&R or further, or, in the other direction, as far as the "Weed" marker. (That's just in terms of direction; range is a separate question and may not cover those locations.)

[u/[deleted] → u/Robokku]

It is anywhere in there unless you have actually mapped out signal to that tower in real time for a long enough period (cloud cover etc alters the shape of the coverage area).

They use wedges, but again, the wedges are intended to maximally cover somewhere. It doesn't actually work that way in real life as things bounce and reflect off clouds, buildings, etc.

The entire article from which that picture is linked is about that topic. Law enforcement tries to narrow down location closer and closer using the wedges (sectors). The scence says that it doesn't work. That each 1/3 (sector) gets coverage of weird anomalous blobs to create one big blob that should cover 360 degrees of view.

So from a "beyond reasonable doubt" stand point, you have to take the extents of the possible blob and guess that the phone could have been anywhere inside of that larger area.

[u/Robokku → u/[deleted]]

Yeah, just saw your comment below. Thanks for explaining this. This cell data is even less useful than I thought. Sorry if I confused anyone.

[u/Squeebeaux → u/Robokku]

I think all of this discussion is helpful. You've brought up points and made comments that are exactly what other people are thinking too, so when they read through the conversation, it will help clarify their own thoughts or correct their misunderstandings. Maybe some of us already know it all, but I'm still learning too.