Fig. 80—A shoal in Hereford Inlet north of Wildwood, N. J., as seen from a height of 10,000 feet. The breaking waves indicate that the shoal is only slightly submerged. (Tidal variation is here about 4 feet.) The sand spit north of the shoal, the south end of Sevenmile Beach, like other spits of the New Jersey coast, is building southward and may in time annex the shoal. Scale, about 1:13,000.
Fig. 81—Sand bars at Cape Charles, Va. South of the town at the right is the harbor, into which a tug-boat is towing a barge. West of the town (left) is a belt of light-colored beach sand and sand bars ending at the south against the breakwater, north of the harbor. The sand bars appear somewhat dim because they were photographed through water. They are under water 1 to 6 feet deep at low tide, or 4 to 9 feet at high tide. Scale, about 1:6,000.
“aerial photo-hydrography.”[12] On the other hand, Volmat reports the successful use of air photography for similar purposes on the French coast, where photographs of objects down to a depth of 17 meters (about 56 feet) were found useful in several ways—among others, the discovery of points of rock which had