The graphic below shows the Alcantarilha phone masts. I don’t believe these phone masts are pivotal in the disappearance of Madeleine McCann, but I would like to use them to explain the problems posed when interpreting phone data, whether that analysis is by the PJ, by Scotland Yard, or by an armchair detective.
The two masts are located a little to the south east of Alcantarilha, on a sweeping curve on the N125. As you can see from the road signs, Alcantarilha is between Portimão and Albufeira.
According to a mobile phone engineer in the PJ files, the area covered by a phone mast is as follows. In towns and large villages coverage is typically 1.5km. Outside it is 5km to 8km. This depends on terrain, obstacles, height etc. A high phone might connect to a distant high mast rather than a closer low mast.
This pattern is going to make things difficult in several ways.
The main location of a phone mast in Luz is on the water tower to the north west of the town. Unfortunately, a 1.5km radius takes in nearly everywhere in Luz, plus most of the village of Espiche to the north of Luz. This aspect of contact makes phone traffic an indicator of rough location. It is far from being a pinpoint tool.
Returning to the Alcantarilha masts, they are 1.5km from the nearest point on the A22. Given the open country range of 5km to 8km, a large chunk of the A22 should be within range. It is not possible to tell from a single contact whether the phone is on the N125, on the A22 or in the town of Alcantarilha.
As it happens, activations here are most likely to be on the A22 (aka the IC4). In 2007 the A22 was toll-free, though this has now changed. In 2007, it made more sense for long journeys to be made on the A22 as that is much faster than the N125. The McCanns made frequent trips to Faro, and there is the trip to Huelva in Spain.
A close up of the water tower at Alcantarilha shows it does not have telecommunications dishes installed on it. There is a significant spike on top, but I presume that is a lightning conductor.
So now we have twin masts and the mess that is the naming convention of the three mobile operators. Rather than a single name, we should have two for Vodaphone. Optimus located masts by parish, so both masts should be covered by a single name. TMN split data into what appears to be mast name/lobe number, giving 3 names per mast, so TMN should be using 6 names for these 2 masts.
This gives a total of 9 names for the twin masts of Alcantarilha. It is fortunate that a detailed understanding of contacts around Alcantarilha is not central to the Madeleine McCann case.
In other places where detailed understanding is essential, the waters get muddied. An inability to tell Luz from the N125 from Espiche is not the best starting point