Web connected RTK GNSS to measure glacier change and flow
Kirk configuring the dGPS node on Breiðamerkurjökull. The white dGPS antenna is on the rod, the small black antenna links it to the base station on the moraine and the small black square antenna on the plate links it to Iridium. The bolts on each leg have not yet sunken into the ice to anchor it.
We are measuring ice flow with the help of new dGPS technologies. Earlier research used dGPS recordings with traditional high cost devices. Our research is using the latest generation of lower cost real-time kinematic dGPS so that more sites can be monitored for the same cost. It also means the loss of one unit in a glacier has a reduced financial impact. Our system automatically provides location measurements from synchonised dGPS units, which wait for a static RTK fix and then sleep between sessions. The readings are sent once per day to a web server via the Iridium satellite network, allowing the system to operate anywhere in the world. The fixes are accurate to around 2cm and they take less than two minutes to acquire, with only 50 bytes to transmit (vs hundreds of kBytes with dGPS recordings). This reduces the power requirements by around a 50th and opens up the possibility of year-around live monitoring.
In 2016 we carried out a simple experiment to track an Iceberg with the help of Formula E. This helped us carry out trials in 2017. Thanks to National Geographic we extended the system in 2018 and monitored into 2020. 2022 sees the start of a new project The role of subglacial soft bed hydrology on glacier response to climate change – It includes ice-tracker2 and UAV/remote sensing.
in 2017 we installed differential dGPS units on two Glaciers in Iceland. Each site has one fixed base station and one moving unit on a glacier. The two are synchronised to wake up when readings are needed. The location data are sent back to the UK via Iridium Satellite messaging and combined with other data to study the glaciers.
The new dGPS units from Swift were linked to an Iridium Satellite-messaging unit (Rockblock) using a Python programmed Espruino Pico computer. See the schematic below for details.
We where able to see the data coming in every day. See our Blog.
Here is a Schematic of our Piksi Multi based node showing how we power up the GPS/Iridium separately when we need them. Also the use of multiple batteries to increase capacity and avoid duplicating power supplies. The Espruino Pico was programmed entirely in MicroPython making it easy to adapt in the field.
Schematic of our RTK dGPS prototype node showing the power control over the GPS and Satellite communications unit. You can you can see separate batteries for each unit. sw = FET switches to control the power.
View inside a rover case when we packed it up for shipping to Iceland – showing our Espruino Pico board (top left), Iridium Rockblock, Piksi Multi (bottom left) with its Freewave radio (bottom right).
In October we swapped the Rockblocks to v3 and reset the base station’s fixed location F1.
If you click on this image and zoom in – the rover is just behind/left of the base GPS antenna.
This is the second Fjalls base station location – covering a wider area of the glacier.
this is the newer position of the Fjalls rover – higher on the glacier but with a good signal from its base station.
distance moved (m) by Fjalls rover. You can see the movement has not slowed down much in winter. Also visible are straight lines where the rover did not send data back.
See our Blog posts on data from Breida
Imaging, GPR and other Surveys
We also carried out a quadcopter imaging survey in order to create a 3D model of the Fjallsjokull margin:
This is our 3DR Solo quadcopter – used for filming and with a Mapir camera to carry out accurate surveys of the ice margin.
This “fly through” was created by moving through the 3D model – it is not a quadcopter video. Models like this can be used to monitor the changes over time as we produce one of the same area each year.
Together with the dGPS units we carried out a GPR survey of the ice being measured at Breida’ and left a timelapse camera observing the ice margin at Fjallsjokull.
Where next?
We’re very happy with the concepts of our design – and many spot measurements do provide good data for analysis. Due to Covid we didn’t deploy new things recently but concentrated on designing a lower power system with better communications capabilities. We look forward to trying the Ublox F9P based system in 2023.