부산대학교 도서관

Over the last year, IBM has extensively used survey quality Global Positioning Satellite (GPS) technology to obtain accurate location data for air emission sources, building and property locations, groundwater wells and risk management plan sensitive receptors. In that time period, IBM has made advances in the use of this technology. The GPS data collected on-site needs to be post processed to remove the effect of the government induced Selective Availability (SA) error. This is accomplished by using a GPS base station at a known location that sees the same GPS satellites over the corresponding time period. Initially, IBM was correcting the data based on remote NOAA CORS GPS base stations located over 60 miles away. Recently, New York State has upgraded the network of accurately located benchmarks as part of the federal High-Accuracy Reference Network (HARN). As part of the HARN network, these high resolution benchmarks in New York State are separated by no more than 30 miles. Using the NYHARN station at the Duchess County airport, and two GPS units, IBM was able to set up an accurate benchmarks on-site. With accurate GPS located benchmarks on-site, the time requirements for collecting site GPS information has been significantly reduced. This is due to the fact that the correcting base station is now on-site and only at the worst case within 1 mile of the sampling location. The time a sample must be taken to obtain survey quality data accurate to the centimeter level depends on how close the sampling GPS unit is to the correcting base station. Using the CORS base stations, samples needed to be taken over 1--2 hours to obtain the required amount of satellite data to correct to the sub-meter level. With the correcting base station now located on-site, survey quality samples can be obtained in 15--20 minutes, thus allowing more samples to be taken in the time it took for one sample in the past.