"You may be surprised to learn that current touchscreens sense only the geometric center of a user’s contact patch, or its centroid, rather than its entire area

"You may be surprised to learn that current touchscreens sense only the geometric center of a user’s contact patch, or its centroid, rather than its entire area, as shown in Figure 2." Not true. This depends very much on the API and the capacitive touch IC in use. The MacBook multi-touch trackpads send out basic shape data (approximated as an oval).