Alongside his colleague Wei Pu, Shen planned to map the orbital paths of the Moon and the planets in an intensive five-year project involving daily observations, yet this was thwarted by political opponents at court. To aid his work in astronomy, Shen Kuo made improved designs of the armillary sphere, gnomon, sighting tube, and invented a new type of inflow water clock. Shen Kuo devised a geological hypothesis for land formation (geomorphology), based upon findings of inland marine fossils, knowledge of soil erosion, and the deposition of silt. He also proposed a hypothesis of gradual climate change, after observing ancient petrified bamboos that were preserved underground in a dry northern habitat that would not support bamboo growth in his time. He was the first literary figure in China to mention the use of the drydock to repair boats suspended out of water, and also wrote of the effectiveness of the relatively new invention of the canal pound lock. Chinese philosopher Mozi (470–391 BC) so far is the first person in history to describe camera obscura (a basic camera). Shen implemented an improved version of the camera, nearly 2000 years later. Shen wrote extensively about movable type printing invented by Bi Sheng (990–1051), and because of his written works the legacy of Bi Sheng and the modern understanding of the earliest movable type has been handed down to later generations. Following an old tradition in China, Shen created a raised-relief map while inspecting borderlands. His description of an ancient crossbow mechanism which he himself unearthed proved to be a Jacob's staff, a surveying tool which wasn't known in Europe until described by Levi ben Gerson in 1321.