21. After several more years of preparation, which involved garnering various permissions to perform the exhumations, the ground survey began in 1998. 22. Mapped by United States Geological Survey ( USGS ) from ground surveys and U . S . Navy air photos 1960-63. 23. An unclassified version of the study, based on data from civilian satellites and airplanes and a ground survey , contains few surprises. 24. He said a team of engineers from Puncak Niaga and a consultant would conduct ground survey to ascertain the exact details. 25. Mapped by United States Geological Survey ( USGS ) from ground surveys and U . S . Navy air photos, 1961-67. 26. Mapped by United States Geological Survey ( USGS ) from ground surveys and U . S . Navy air photos, 1960-62. 27. A ground survey team discovers a vast subterranean energy network with a power source located some 500 kilometers from the ship. 28. Mapped by United States Geological Survey ( USGS ) from ground surveys and U . S . Navy air photos, 1960-63. 29. Officials say counting is a lengthy process of aerial and ground surveys that need to take account of seasonal migration patterns. 30. The annual census of the species involves aerial and ground surveys and educated estimates based on the number of observed birds.
