| Abstract: | Land subsidence measurement is usually based on a comparison of bench-mark elevations surveyed at different times. These bench marks, established for mapping or the national vertical control network, are not necessarily suitable for measuring land subsidence. Also, many bench marks have been destroyed or are unstable. Conventional releveling of the study area would be costly and would require several years to complete. Differences of as much as 3.9 ft between recent leveling and published bench-mark elevations have been documented at seven locations in the Sacramento Valley. Estimates of land subsidence less than about 0.3 ft are questionable because elevation data are based on leveling and adjustment procedures that occured over many years. A new vertical control network based on the Global Positioning System (GPS) provides highly accurate vertical control data at relatively low costs, and the survey points can be placed where needed to obtain adequate areal coverage of the area affected by land subsidence. |
| Genre: | Article |
| ProdID: | 70016162 |
| Citation Author: | Blodgett, J. C.; Ikehara, M. E.; Williams, G. E. |
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| Citation End Page: | 130 |
| Citation Issue: | 2 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Surveying Engineering |
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| Citation Number Of Pages: | 19 |
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| Citation Publisher: | ASCE |
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| Citation Search Results Text: | Monitoring land subsidence in Sacramento Valley, California, using GPS; 1990; Article; Journal; Journal of Surveying Engineering; Blodgett, J. C.; Ikehara, M. E.; Williams, G. E. |
| Citation Start Page: | 112 |
| Citation Volume: | 116 |
| Citation Year: | 1990 |
| Type: | citation/reference |
| Text: | Monitoring land subsidence in Sacramento Valley, California, using GPS; 1990; Article; Journal; Journal of Surveying Engineering; Blodgett, J. C.; Ikehara, M. E.; Williams, G. E. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1061/(ASCE)0733-9453(1990)116:2(112) |
| Date Other: | Mon, 1 Jan 1990 00:00 -0600 |
| Publisher: | ASCE |
