Why the perimeter LED display had to be standing with an angle for more than 10 years ago?

Now the FIFA world cup is keep going on, did you notice that the perimeter LED display? Nowadays, the perimeter LED display is standing up straightly, but they standing with an angle for many years ago and even today in some projects, do you know why?

2 reasons:

1. The technology of the LED lamp widely used is DIP technology for 10 years ago, the DIP lamp has high brightness but the viewing angle is small, only 90 degrees on the vertical, because there is hat brim over the LEDs. We need to make the perimeter LED display standing with an angle in order to let the audiences watch the full advertising directly and easily.
2.  The stadium field is small. Like in the football field, it’s very big and far away from the audiences to the perimeter LED display, so it’s no problem for the perimeter LED display standing up straight. But in the basketball field, the audiences is much higher than the perimeter LED display, the perimeter LED screen may need to be standing with an angle for making audiences watch the ads clearly.

The perimeter LED display installed with an angle is all because of the LED display’s viewing angle, and the viewing angle base on these 2 reasons.

One question for you, do you know from which year the perimeter LED display started to be used by the FIFA world cup for Ads?