More sea ice reconstructions

Because we all focus so hard while writing workshops, right? Here are a couple more ‘fun with sea ice’ visualisations. There’s nothing really scientific about these, they’re based on some proof of concept work which is very slowly iterating toward science.

So, just enjoy! Firstly, SIPEX II Ice station 7 – made from crossing-over flights.

It’s pretty! And you’ll notice that all the heights are referenced to an ellipsoid. It’s not a rigorous science dataset in this incarnation.

Next, a strip mapping test over progressively thin ice at the edge of a polynya:

You can see the ice getting progressively darker toward viewers right, as it thins. If you view by elevation – you can also see some inherent issues with single-strip mapping and loose camera calibration – it’s pretty warped. So we learn, see if it works, and hopefully get to try again another day.

Ice floe interactive visualisation, take 1

I recently spoke at POLAR2018 about using aerial photography for observing the properties of snow on sea ice. I’d really hoped to present some new work I’d been trying out on estimating local curvature, roughness and other properties from high resolution 3D models of sea ice topography.

Unfortunately I didn’t get all the way there. Firstly, I reprocessed a bunch  of data and the results were worse than work I’d done in the past. So back to the drawing board, and the fallback position of explaining a bunch of work we’ve done over the past decade. A PDF of my slides is available via researchgate, but preferentially wait for the interactive web version to finish – it’ll be more up to date, have better links and side notes!

I did, however, put together the beginning of a 3D visualisation for sea ice from the surface (using photogrammetric reconstruction) and below (from upward looking sonar). Click and drag below to move/zoom around; and expand the hamburger menu at top left to expose more navigation tools, measuring tools and styling options. Or, click here to open a full page view.

Many thanks to the Antarctic Climate and Ecosystems Cooperative Research Centre for funding the work behind this; and for getting me to Davos.

Drifting sea ice and 3D photogrammetry

3D photogrammetry has been a hobby horse for ages, and I’ve been really excited to watch it grow from an experimental idea [1] to a full-blown industrial tool. It took a really short time from research to production for this stuff. Agisoft Photoscan turned up in 2009 or 2010, and we all went nuts! It is cheap, super effective, and cross-platform. And then along came a bunch of others.

Back to the topic – for my PhD research I was tinkering with the method for a long time, since I had a lot of airborne imagery to play with. I started by handrolling Bundler + PMVS, and then my University acquired a Photoscan Pro license – which made my life a lot simpler!

My question at the time was: how can we apply this to sea ice? or can we at all?

The answer is yes! Some early thoughts and experiments are outlined here, and below are  some results from my doctoral thesis, using imagery captured on a 2012 research voyage (SIPEX II). Firstly, a scene overview because it looks great:

Next, stacking up elevations with in situ measurements from drill holes from a 100m drill hole line on the ice. The constant offset is a result of less-than-great heighting in the local survey – I focussed heavily on getting horizontal measurements right, at the expense of height. Lesson learned for next time!

And finally, checking that we’re looking good in 3D, using a distributed set of drill holes to validate the heights we get from photogrammetric modelling. All looks good except site 7 – which is likely a transcription error.

How did we manage all this? In 2012 I deployed a robotic total station and a farm of GPS receivers on drifting ice, and used them to make up a lagrangian reference frame (fancy word for ‘reference frame which moves with the ice’) – so we can measure everything in cartesian (XYZ) coordinates relative to the ice floe, as well as using displacement and rotation observations to translate world-coordinates to the local frame and vice-versa. Here’s a snapshot:

I don’t know if this will ever make it to publication outside my thesis – I think the method should be applied to bigger science questions rather than just saying ‘the method works and we can publish because nobody put Antarctica in the title yet’ – because we know that from other works already (see [2] for just one example).

So what science questions would I ask? Here’s a shortlist:

  • can we use this method to extract ridge shapes and orientations in detail?
  • can we differentiate between a snow dune and a ridge using image + topographic characteristics?

These are hard to answer with lower-density LiDAR – and are really important for improving models of snow depth on sea ice (eg [3]).

For most effective deployment, this work really needs to be done alongside a raft of in situ observations – previous experience with big aircraft shows that it is really hard to accurately reference moving things from a ship. That’s a story for beers 🙂



[2] Nolan, M., Larsen, C., and Sturm, M.: Mapping snow depth from manned aircraft on landscape scales at centimeter resolution using structure-from-motion photogrammetry, The Cryosphere, 9, 1445-1463, doi:10.5194/tc-9-1445-2015, 2015

[3] Steer, A., et al., Estimating small-scale snow depth and ice thickness from total freeboard for East Antarctic sea ice. Deep-Sea Res. II (2016),

Data sources


Dr Jan Lieser (University of Tasmania) instigated the project which collected the imagery used here, let me propose all kinds of wild ideas for it, and was instrumental in getting my PhD done. Dr Christopher Watson (University of Tasmania) provided invaluable advice on surveying data collection, played a massive part in my education on geodesy and surveying, and also was instrumental in getting my PhD done. Dr Petra Heil and Dr Robert Massom (Australian Antarctic Division) trusted me to run logistics, operate a brand new (never done before in the AAD program) surveying operation and collect the right data on a multi-million dollar investment.  The AAD engineering team got all the instruments talking to each other and battled aircraft certification engineers to get it all in the air. Helicopter Resources provided safe and reliable air transport for instruments and operators; the management and ship’s crew aboard RSV Aurora Australis kept everyone safe, relatively happy, and didn’t get too grumpy when I pushed the operational boundaries too far on the ice; and Walch Optics (Hobart) worked hard to make sure the total station exercise went smoothly.






Acquiring prism lock: the cover photo

The cover photo for this site shows.. the back of my head, a Leica Viva TS 15, a prism, and a bright yellow, low cost, very effective instrument warming/battery box I’m very proud of! I’m acquiring prism lock using the remote control, before heading out to collect locations on a SIPEX II ice station. The sea ice surveying project was part of my work for the Australian Antarctic Division, and complements my PhD studies. It was a challenging task – nobody knew if the total station would play happily at -20 degrees celcius on drifting sea ice. It performed admirably, and the results will provide much-needed spatial glue for on, over and under ice spatial datasets collected on the voyage. Photo: Polly Alexander