No circular shadow of the saucer can be seen. Only the hexagonal shadow of the legs.
During the fight in the car between John Carter and the alien, the steering wheel moves visibly from side to side, showing that it is only loosely anchored to the prop dashboard.
Whenever The Invaders' UFO is on the ground, the shadow beneath it is angular, not the circle one would expect to see under the saucer. This indicates that the landing legs were merely attached to a platform, a "live" set with which the actors could be filmed. The miniature of the saucer exterior was matted over the platform later.