There is also a deficiency with respect to control point distributions over the aerial block. While it is common to fully surround the area of interest with control points, this is not the case in coastal mapping, as control points are usually only measured in land, but not the sea bottom. The problem may be solved if control points on the sea bottom are acquired somehow, otherwise, appropriate flight design and additional cross-flight lines may reduce the effect. The last, but not least limitation is posed by the medium itself; water clarity is not always given and the light penetration defines the maximum depth to be surveyed. Typical photogrammetric problems, such as photo matching in texture-less areas, are still valid in an underwater environment, especially in sandy sea beds.