C.-C. Chen | USGS Science

USGS2006

Automatic alignment of vector data and orthoimagery for the national map

A general problem in combining road vector data with orthoimagery from different sources is that they rarely align. There are a variety of causes to this problem, but the most common one is that the latest products are collected with higher accuracy and improved processing techniques. In previous work, we developed techniques to automatically correct the alignment of vector data with orthoimagery using a technique called conflation. However, in applying our technique to real-world datasets provided by USGS, we discovered that these techniques failed in some areas. In this paper, we describe some refinements to our original approach that provide consistently better results in aligning the vector data with the orthoimagery.

Conference Paper↗

USGS2000

Performance of the Taiwan Rapid Earthquake Information Release System (RTD) during the 1999 Chi-Chi (Taiwan) Earthquake

A major earthquake occurred near the town of Chi-Chi in Nantou County, Taiwan, at 1:47 am (local time), 21 September 1999, about 150 km south of Taipei. This is the largest earthquake to have occurred on land in Taiwan during the 20th century. Although Taiwan has an earthquake building code, thousands of buildings collapsed due to the earthquake, leaving more than 100,000 people homeless. The death toll exceeded 2,300 with more than 10,000 injured. Within 102 seconds after the earthquake's origin time, a good estimate of the hypocenter (23.87° N, 120.75° E, Depth = 10 km) and magnitude ( M L = 7.3), and a shaking map were determined automatically by the RTD system. The result was immediately disseminated to governmental emergency response agencies electronically in four ways, by e-mail, World Wide Web, fax, and pager. This rapid information system has been successfully operating in Taiwan for more than four years. During the Chi-Chi earthquake, the rapid availability of earthquake information facilitated the emergency response. The RTD system worked very well throughout the whole aftershock sequence (several aftershocks had local magnitude of 6 or larger). Again this timely information was useful to the emergency response teams. In this paper, we briefly describe the RTD system and summarize its performance during the Chi-Chi earthquake.

Seismological Research Letters↗