Tar Heels first to check satellite data on small rivers

在2023年10月一个迅速变暖的日子里, Sophia Harvey waded into the muddy water of California’s Owens River to anchor a GPS receiver on a tripod. She and three Carolina classmates were gathering data on the river’s water level to compare with data from NASA’s new Surface Water and Ocean Topography satellite.

自10个月前推出以来, the SWOT satellite has orbited Earth at an altitude of over 500 miles to measure water surfaces worldwide. It yielded data on oceans, rivers and streams in precise detail never seen before. NASA and its partners at France’s space agency designed the satellite to survey rivers and streams that are wider than 50 to 100 meters, showing details such as the slope of a stream’s flow and the height of the water in it.

研究ers were surprised by the satellite’s ability to register smaller rivers, but no one had compared SWOT data for the smaller rivers to on-the-ground measurements. The opportunity to do so came when students in a first-year seminar taught by Drew Coleman, 艺术与科学学院地球系教授, 海洋与环境科学系, prepared for a re太阳城娱乐城 trip to California’s Owens Valley near the Nevada border.

Tamlin Pavelsky, a freshwater re太阳城娱乐城er and professor in the same department who leads the hydrology science team for NASA’s SWOT mission, knew that the satellite would pass over the valley when the class was there. Pavelsky asked Coleman if the students could perform some of the first ground-truthing of satellite data by measuring water levels along the Owens River, 宽度在6到15米之间.

科尔曼同意. Pavelsky’s lab staff trained Harvey and classmates Talia Benjamin, Kate Merrin and Jackqueline (Jack) Wilson on setting up global navigation satellite equipment. 一天之内，他们参观了三个地方, setting up a receiver to measure water surface elevation for an hour. The device received signals from the same GPS satellite constellation that smartphones use, 但准确度更高. The students used these GPS signals to capture the precise height of the water surface above sea level with an accuracy of a few inches.

然后，学生们将他们的太阳城娱乐与SWOT数据进行比较. “两个地面测点, the average height of the water surface elevation data points SWOT picked up had a discrepancy of less than 1 meter compared to our data and a discrepancy of 3 meters at the other,他们的报告写道。. “Additionally, SWOT could accurately approximate the river’s slope, yielding a 0.1米/公里误差. 虽然必须收集更多的数据, these findings suggest SWOT may be capable of surveying narrower rivers than initially expected.”

“It’s hard to comment on precision and accuracy when we visited so few spots along the river,哈维说。. “But SWOT may have the potential to tell us important things about discharge and water availability on narrow rivers that impact ecosystems or human use.”

帕维尔斯基与美国宇航局分享了学生们的太阳城娱乐, which acknowledged that the data suggested that SWOT can provide useful water surface elevation data on relatively narrow rivers. 据我所知, their work was the first time anyone had compared SWOT elevations on such a narrow river to on-the-ground measurements of water surface elevation,他说.

科尔曼的班级产生了四个与swat相关的项目. “All of the projects were ground-breaking, and this one stood out. It is truly UNC undergraduates contributing to international re太阳城娱乐城. And they were first-year students, no less,” Coleman said.