 A Continental Network
George Davidson lived through the San Francisco earthquake in 1906. He removed the telescope from his private observatory in the city to allow the building to be used as emergency shelter for women and children left homeless by the fire. There were extensive geodetic re-surveys of the primary triangulation network made, to discern earth movements along the San Andreas Fault. One set of measurements supported Davidson in a dispute that went back decades. He had surveyed the peak of Mount Tamalpais in the 1850s. A subsequent survey, in the 1870s, found a discrepancy in his positioning. He asserted that his measurements were accurate, but that the mountain had moved. The re-survey after the 1906 earthquake confirmed that he had indeed been correct.
A hundred years ago, in 1907, Davidson made his last journey to Alaska, exactly 40 years after his initial trip in 1867. He made the first trip because he had been asked to advise Congress whether the nation should purchase Russian America, as it was then called, from Imperial Russia. His favorable report tipped the balance. The United States acquired Alaska, and, of course, the Coast and Geodetic Survey then was given responsibility for charting its coast and islands.
How might he have reflected about his life in his steamship cabin on that last long voyage back to San Francisco? By that point he had received every honor imaginable in California--president of the California Academy of Sciences, regent and professor of the University of California, a member of the state's Earthquake Commission, a senior advisor to the state on water systems and irrigation, and more. From his letters and published writings, however, these matters paled compared to the pride he felt in the quality of the geodetic network he created to describe the state's topography.
All his initial local networks, starting with the tent observatory site at Point Conception, had been corrected and connected into a continental network that, in evolved form, is the framework for all geopositioning today. When we press a button on a GPS receiver to find out where we are, we do so relative to Davidson's geodetic framework. Davidson also took enormous pride in the visible expression of the network, the many changing editions of the maps and charts produced by the Coast Survey. The coast is the most dynamic environment on the planet, and every chart of it is a complex snapshot of changes continually underway.
Changing Priorities
In 1869, Henry Mitchell, who was the chief hydrographic scientist in the Coast Survey, published a treatise on reclamation of tidelands as an appendix to the Survey's annual report. He described the context of change well under way on the Atlantic Coast, but only then beginning in California. In the East, Mitchell said, the rapid development of railroads and wagon roads was changing every aspect of coastal life, previously based exclusively on large and small boats. Estuary channels that had been major thoroughfares became literal backwaters once the villages near them could be reached easily by land. This made for great cultural and ecological stresses, as watercourses began to be seen as potential agricultural land, once the waters were drained away. Rival and incompatible uses of the coast were proposed. Local preferences had also to be balanced with larger constituencies, as draining wetlands in one place could affect flooding in another. As Mitchell noted:
"Were the entire value of a water-course always to be measured by its service, as an avenue for 'market men,' the conversion of its territory from commercial to agricultural uses would be generally popular as soon as the bed of a stream became more valuable than its water, and no strife would occur; but in most cases there are other interests involved which are antagonistic to this change, viz: the trade in foreign or distant products, the fisheries, &c. Sometimes, too, an arm of the sea which has ceased to be of use to the residents upon its banks has still a national value as a harbor of refuge or as a thoroughfare."
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