Crowd means a large number of persons gathered together, however I've found some examples in which this expression is used "a large group of crowd".
In the future, these flying drones may be seen inspecting pipes or flying over a large group of crowds, streaming images. A Dragonfly Robot Taking Off
It's very rare to see large group of crowds congregating in one place in Seattle, the Folklife Festival is one exception.
It seems such usages are redundant, such as "large group of groups". My question: is this grammatically correct to use such expression?