A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by providing an impact signal if the impact meets threshold impact criteria. The impact signal identifies an expected location of a print area (118) in the zone and supplemental impact information for the impact. Responsive to the impact signal, a controller (702) determines whether the supplemental impact information meets supplemental impact criteria and, if so, provides an initiation signal. The impact-dependent portion responds to the initiation signal, if provided, by temporarily appearing along the print area as changed color materially different from the principal color. The print area closely matches the object-contact area in size, shape, and location.

A variable-color region (106) of an information-presentation structure extends to an exposed surface (102) at a surface zone (112) and normally appears along it as a principal color. An impact-dependent portion (138) of the variable-color region responds to an object (104) impacting the zone at an object-contact area (116) by temporarily appearing along a closely matching print area (118) of the zone as changed color materially different from the principal color if the impact meets threshold impact criteria. Object-tracking apparatus (808) tracks movement of the object over the surface and provides an image-causing tracking impact signal when the object impacts the zone according to the tracking. An image-generating system (802, 842, 1152, or 1182) responds to at least the impact signal by generating a print-area vicinity image consisting of an image of the print area and adjacent area of the surface.

Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.

The present invention is related to a sport post associated with a goal, a score or finish line, and a method of using the sport post. The sport post includes at least one post defining at least one slot along a longitudinal axis of the post. The post is substantially aligned with an edge adjacent a sport area associated with a sport surface for determining a sport condition of a goal, a finish or a score. At least one transparent member is received through the slot, and has a configuration so that at least a portion of the edge is visible through the transparent member. The sport post can be associated with a system including a reflective strip on the sport surface, an electromagnetic radiation transmitting device and a detection device for determining if a sport element crosses the edge.

Disclosed is system and method for measuring the tension of a tennis net, and, alternatively or in addition, for determining if a service let occurs via the measuring of the net tension. The disclosed embodiments measure a force exerted on the center-strap or the singles stick by the net. In these embodiments, the measured force provides an accurate reflection of the tension of the net.