了解融雪

Author:Renata BarradasGutiérrez

Regions of the Canadian Arctic are experiencing unprecedented warming as a result of the greenhouse gases emitted by human activity. The western Arctic specifically has experienced significant increases in near surface ground temperatures over the past few decades, almost twice that of the global average temperature increase. This warming trend has resulted in significant changes to the regional ecosystems and the physical processes operating across these environments.

To better understand how the Arctic tundra will respond under further climate change scenarios, members of the Marsh Lab Trail Valley Creek (TVC) research group from Wilfrid Laurier University in Canada led by Dr. Philip Marsh travelled more than 4,000 kilometres to study the changing hydrology of Canada’s western Arctic using Leica Geosystems GNSS instruments. The research collects data on all components of the water cycle and aims to understand how further temperature increases will affect the local and regional freshwater systems by combining:

• detailed field observations
• 遥感
• GNSS positioning and modelling.

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Survey time

作为雪的水的年度输入是水文循环的最重要方面，也是北极溪流和湖泊系统的最大淡水贡献者。在冬季结束时，在4月至5月中旬之间，沼泽实验室TVC研究人员进行了雪调查，测量了多个研究盆地的雪深和储水。一组研究人员准确地测量了在冬季积累的年度降雪，以量化液体水储存量（以雪水等效的量测量，并计算一旦雪融化，水文系统可用的水量。

To better understand the heterogeneous nature of the tundra snow cover, Marsh Lab TVC researchers use many recent technological advances, including:

• Unmanned aerial vehicles (UAVs)
• aerial based snow depth data
• 自动化雪depth recording probes
• experimental cosmic ray neutron probe stations.

目前的研究小组使用了两个莱卡GS10 GNSS receivers and two CS20 field controllers to collect point type data for a wide variety of research projects. With Leica Captivate field software, the team collects and organises the data while Leica Infinity survey software is used to project and filter the collected field points, ensuring data is stored in the correct coordinate system. UAV post processing software is also used.

“Our field work relies heavily on obtaining high accuracy spatial datasets and our Leica Geosystems GNSS system makes all of this work possible,” said Branden Walker, Research Associate at Wilfrid Laurier University. “Previously using Leica Geosystems instruments at other research sites with excellent results, we chose to go with them again for this project.”

The group of researchers also used the GS10 GNSS receivers and CS20 field controllers for regular surveying of ground control points, and surveying topographic changes for ground validations and change detections of permafrost features.

“The majority of our ongoing research projects are centred on obtaining highly precise and accurate GPS data,” said Walker. “Compared with other data sets, Leica Geosystems GNSS systems have proven to provide robust and reliable data.”

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Collecting data form above and below

One of the main methods for measuring the snow across larger areas is through the experimental use of UAVs. In order to validate, georeference and correct the GNSS data from the UAV, Marsh Lab TVC researchers need to measure the actual Snow and Ground Surface Elevation on the ground using a Leica Geosystems GNSS system for surveying ground control points with UAV mapping points with a high level of accuracy. These highly precise ground control points are then processed in Infinity survey software and a photogrammetry software to improve the accuracy of the UAV mapping points.

“The Leica Geosystems GNSS system we use allows us to create ground control points with a known position with sub-centimetre accuracy. This is very important for correcting our elevation products from the UAV, which may only differ from one flight to the next by a few centimetres,” said Walker. “This data allows us to quantify snow depth and water storage with previously unobtainable spatial and temporal resolutions. The data from our UAV is post processed and georeferenced using ground control points collected with our Leica RTK system to produce highly precise and accurate spatial datasets.

“Our Leica Geosystems instruments are the backbone of our research programme. The precision and accuracy provided by our GNSS instruments provides the spatial data required to map small scale variations in snow depth using the UAVs and helps us to save time in the field when setting up and collecting data points.”

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帮助地球的水图任务

The research conducted by Marsh Lab TVC researchers using Leica Geosystems GNSS systems will also be the main ground validation for Air Surface Water & Ocean Topography (AirSWOT) in North America, a component of NASA’s Arctic Boral Vulnerability Experiment (ABoVE). The AirSWOT validation mission measures the surface height of water on as many lakes as possible during flights. AirSWOT is part of SWOT mission to map Earth’s water from space to know how much fresh water there is on Earth and to calculate river flow rates and monitor coastal ocean currents.

NASA的空气现象学空中雷达遍及加拿大北部和阿拉斯加，测量了数以万计的水体水面高于250米的水体。对于Airswot任务，该团队有一个小窗口来捕获所需的测量值，因此他们必须具有快速可靠的GNSS仪器，能够从远距离范围内测量。

“The reliability of the rover to make quick and accurate measurements several kilometres from the base gives me confidence we will be able to validate NASA’s AirSWOT data successfully,” said Evan Wilcox, MSc Geography Candidate at Wilfrid Laurier University.

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Training field researchers

Marsh Lab TVC hosts research groups from North America and Europe who study Canada’s arctic regions. Wilfrid Laurier researchers regularly help train student researchers on how to use Leica Geosystems products.

“Being part of a university led research group also results in a high student turn around, so the simplicity and intuitive design of Leica Geosystems products makes training the next round of field researchers and students much easier – again, saving our group time and money in the long run,” added Walker.

此外，恶劣的北极条件可以推动大多数设备的限制。Leica GeoSystems GNSS接收器和CS20场控制器设计为在最极端的条件下执行。

沃克说：“我们的现场工作的性质将所有工具都带到了它们的绝对突破点和最高点。”“我们的Leica GNSS系统已经在各种恶劣的北极条件下工作，包括-20°Celsius的温度。”

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关于气候变化的可靠信息

在借着利卡地地理系统的准确性和精度后支持，研究人员对北极苔原系统如何发生了更大的了解，这是由于气候变化导致的空气温度升高而发生了变化。需要准确而可靠的数据，以更好地了解雪深，雨水，湖泊水平，植被，多年冻土和流量之间的复杂关系，以及在发挥作用的物理过程，以便能够使用数学模型预测未来的变化。

目前，众多研究科学家和研究生目前正在使用这项研究生成的数据，重点是测试和验证新的数据收集技术。获得的信息还为一个长期的研究项目做出了贡献，该项目收集了北极苔原的历史数据集。了解北极的水文过程将提供有关气候变化如何链接湖泊水平，溪流和积雪以及这如何影响加拿大人生活的可靠信息。