Trimble GPS Tutorial - Location

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Location

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"Where am I?"

The first and most obvious application of GPS is the simple determination of a "position" or location. GPS is the first positioning system to offer highly precise location data for any point on the planet, in any weather. That alone would be enough to qualify it as a major utility, but the accuracy of GPS and the creativity of its users is pushing it into some surprising realms.

Knowing the precise location of something, or someone, is especially critical when the consequences of inaccurate data are measured in human terms. For example, when a stranded motorist was lost in a South Dakota blizzard for 2 days, GPS helped rescuers find her.

GPS is also being applied in Italy to create exact location points for their nationwide geodetic network which will be used for surveying projects. Once in place it will support the first implementation of a nationally created location survey linked to the WGS-84 global grid.

The Italian Grid

Using Trimble SSE GPS receivers, the Italian Military Geographic Institute is creating what is reputed to be the first nationwide geodetic network . This grid is based on the WGS-84 global grid, a mathematically created grid that surrounds the earth. While this global grid is accurate enough for geodetic research and measurements, it lacks the precision for local and regional projects.

With the addition of GPS location data collected using Trimble systems, surveyors will no longer have to perform preliminary surveys to calculate differences between WGS and local survey data. This is the first case of a national survey organization creating data that's linked to WGS-84. This project is paving the way for similar networks in Europe and possibly around the world.

Sometimes an exact reference locator is needed for extremely precise scientific work. Just getting to the world's tallest mountain was tricky, but GPS made measuring the growth of Mt. Everest easy. The data collected strengthened past work, but also revealed that as the Khumbu glacier moves toward Everest's Base Camp, the mountain itself is getting taller.

The Man Who Measured Everest

Most people wouldn't blame Brad Washburn if he retired to rest on his laurels, "said Paul Perreault, Washburn expedition member and Trimble employee. "At 83, he's climbed Alaska's Mt. McKinley many times, logged the first ascent of Mt. Baker and Mt. Sanford, and in his spare time has served as founder and director of the Boston Museum of Science." But there was one more thing Dr. Washburn wanted to accomplish: to measure the growth of Mt. Everest, the world's highest mountain.

In early 1995, Dr. Washburn and his team made a series of measurements using GPS between well-established survey marks in the Himalayas. Their goals were to make solid GPS observations to verify past work, make the first long-term GPS observations above 25,000 feet, and use GPS to determine the flow of Everest's Khumbu glacier.

Many GPS systems were installed on and around the mountain, and a wealth of data was collected about the location and position of key landmarks and survey points. Unfortunately, the climbing team ran into very deep and soft snow about 1000 feet below the summit, and no GPS data was collected at the peak itself. A major effort to complete this system all the way to the summit will be made in May 1996.

The expedition was an incredible test of people and equipment, and the U.S. and Nepali climbers were the finest in the world. The receivers installed around the mountain collected data for over 12 hours under conditions that challenged their engineering. And the team enjoyed the side benefits, too - many breathless moments at 18,000 feet and above, looking out over the most spectacular and majestic scenery in the world.