Mapping the ground

You'll have to take my word for it, I'll never find a reference for this story. Ireland was mapped in the 19thC by teams of land-surveyors: chains, theodolites, triangulation and wet socks. Cost of labour has rocketed since the 1840s, so when the Ordnance Survey of Ireland needed to update their maps 30 years ago - because the pace of change and development was hotting up and the 1911 survey didn't show a rattle of by-passes, bridges and housing estates. This obsolescence of old paper maps benefitted me last year when I purchased the whole SE corner of Ireland at 1:50,000 scale. So the OSI put out to tender a contract to capture the landscape in precise series of overlapping aerial photographs. The company that won the tender had looked at Irish weather, the size and speed of their Cessna and reckoned that they would budget 18 months to be sure to be sure of getting enough cloud-free days to cover the country. They started in early Summer in the midst of a rare anticyclone, flew all the hours of daylight and finished the task 15 days later: Win!

The gossip is that the Department of Agriculture does it all by satellite now, snapshotting every field every five days. That may be just a rumour to stop farmers burning their hedge-clippings and throwing their plastic silage wrappers into the bonfire. You may be certain sure that the Dept Ag doesn't have the manpower to analyse all these data: they are too busy drinking tea and doing sudoku at their desks.

Photo-technology has moved on mightily since the 1990s. You just think Google Streetview. My students capture the view down their microscopes with their smartphones . . . which is a little annoying. One of the most amazing technologies matches the macro with the micro and uses LiDAR to detect minutes variation in height over swatches of countriside - even when the hard surface is masked by vegetation. We know what LiDAR is and how it works but their isn't consensus on what the acronym means; eithee  light detection and ranging OR light imaging, detection and ranging. See The Blob on APGAR for a backronym.

The UK Environment Agency has taken out a contract to map the whole country from the air using LiDAR. They are hoping to discover wonders like the layering of a modern motorway and a 19thC farmstead on top of a Roman fort and its associated access roads [L].  Bloomin' amazin'. The amount of data when you map the entire country at 1 metre resolution is impossible to store, let alone process, without a huge server. But these data are going to be made freely available to industry and Josie Public and you may bet your sweet bippy that the data are going to be put to some quite unforeseen creative use.  there are 11 terabytes of data in it which has been downloaded 500,000 times and stored on another server somewhere else. That's a LOT of bytes. But it still is a microdot compared to the trillion crap photos which are uploaded to The Cloud every year . . . never to be seen again.
In England, even if there are some occluding trees, you can still get access to the interesting sites for field work on the ground. It's a bit different in the Central American jungle where the storied vegetation fills the sky from ground to 50m up and then cascades down again as lianas, vines and thorns.  With LiDAR you can strip away the jungle to reveal a whole network of interconnected Mayan cities where nowadays only people with blow-guns hunt for a bit of bush-meat. And the mapping data doesn't stay on the server; chunks of it can be downloaded onto a laptop to create a virtual reality landscape linked to GPS. The archaeologist can image the next pyramid invisible in the impenetrable jungle and make a direct bee-line for the gods of the Maya. Asombrosamente increíble!

drone scope boyne henge scape

The Bend in the Boyne Brú na Bóinne is richer in neolithic structure than anywhere else in Europe. It knocks our wee Neolithic Ringstone into the ha'penny place. Newgrange is the cherry of the artifacts partly because it was 'restored' in 1967-1974 from an ould hape to a structure with a dazzling white wall of quartz which may have existed 5,000 years ago in the same place. The currants in the local landscake are the similar but less impressive, less tricked-about mounds at Dowth and Knowth and dozens of rings, lines, pits, holes, ditches, banks which can be picked up if you know where and how to look [source for more detail].  or Maybe Boyne Valley Landscapes Project Phase III Final Report 2010 by Davis, Megarry, Davis, Barton from The Heritage Council INSTAR Program.
That picture is taken with LiDAR [bloboprev] which captures and exaggerates minute variations in the height of the ground: ignoring plant cover which might be taller than the maximum soil-height difference.
You can see every wart and suture in the landscape EVERYTHING . . .you might think. Because you'll agree that, for the whole field nearest to the extreme SW [bottom left] corner [clipped out L], it's a case of nothing to see here, folks. But you would be wrong because there are other ways of seeing the landscape, with different tools, at a different time, with a different mindset. Anthony Murphy is a local man, a sub-editor on the Farrrrmer's Journal, who has been fossicking about the North of Co Meath for nearly 20 years, looking at things sideways and talking to people and reading books . . . and writing them, and taking photographs and running a website all about the interface between human history, myth and the landscape called Mythical Ireland. A couple of years ago he got a drone and started to look at things from above. And then we had a punishing drought and he took out his drone because of the drought-marks being reported in the UK.  He snapped a picture of that same-old same-old field and found a 'new' circular structure where none was documented before:Gobsmacked, he was:“When I saw it first I was like ‘what’s that? What the hell is that?’ It’s something I had never seen before. It is huge.”
I've turned it upside down to make it clear how the new henge - sacred enclosure - fits into the busy landscape. The circles at the right edge of each picture are the same thing. It was suggested on the wireless, not entirely as a joke, that these henges might have been a 2,000 capacity sports ground rather than a place of religious ritual. Then again, sport and religion blend into each other is a rather uncomfortable way. The drought exaggerates any discrepancy in the water-retaining capacity of the soil. The surface of the field after thousands of years of rainfall and windstorm and, especially, ploughing is flat like a billiard table and so LiDAR-opaque. But the 200m wide circle of wooden pillars sunk into holes 4,500 years ago has changed the soil, its microbial community and its porosity forever. More coverage, better pics: RTE; BBC; RIA; Twitter; Indo; 

Turlough

Y'll need some background music to this, what better than a compendium of Turlough O'Carolan Toirdhealbhach Ó Cearbhalláin (1670-1738) Sí bheag, sí mhór - Planxty Irwin -  Eleanor Plunkett - Farewell to Music.

Almost the last talk at the EnvSciCnf this week came from the Geological Survey of Ireland GSI, one of Ireland's most productive government quangos. It was a report on the 400 examples of 'groundwater flooding'. This is when water comes blurfing out of the ground instead of either falling from the sky or travelling by beck rill stream and river through on its way to the sea. They only occur if the underlying rock is super soluble limestone karst: the water dissolves the calcium carbonate CaCO₃ so that it becomes a complex network of sub-surface fissures. Given several thousand years, the fissures grow into interconnected tunnels and caves like Mitchelstown. Limestone cave-systems are thus always connected with and by water: as my pal Roy found in his near-death experience in Sleet's Gill. Groundwater flooding is when, hours or days after a good spill of rain, the underground network fills up and spills out of the top to flood the landscape. In Ireland these temporary lakes are called turloughs and they look like this:

Joan Campanyà <trigger Catalonia> of the GSI is The Effective in project GWFlood tasked to map the turloughs in space and time, so that all the stake-holders have a good idea about when and where and how deep water will appear. We have a pretty good idea of the location of all the [N=400] places where a turlough has ever appeared, but some of these locations are up a rough bohereen in Co. Roscommon and [so] there is no continuous record of their ups and downs and disappearance. There are two main techniques

• Put a sufficiently tall pillar in the lowest part of the local landscape. Incorporate an electronic dip-stick in the bottom and a radio-telemetry beamer on the top and an hourly report of water-level can be captured in GSI head office.
• Satellite  mapping with LiDAR [prev] and SAR - synthetic aperture radar.

This before and after picture-pair caused an audible WTF?gasp at the conference - to which I contributed. In a dry summer, the landscape is covered in grass and quietly chomping cattle belching us all into oblivion with their methane-laden burps. In a typical winter windsurfers can scud across the choppy waves. Rahasane turlough in Galway is 2500 ha in extent. My post-talk question was "how often must you change the batteries?" A: never nowadays because each post has a solar charger. Nevertheless setting up 400 wet-depth poles doesn't scale up from the N=20 pilot study. This is where SAR kicks in with its ability to detect back-scatter;

SAR-sat directs a radar beam to earth as it passes over the landscape. IF it strikes flat water THEN radar-waves bounce off and awaaaay [the angle of incidence is equal to the angle of reflection] ELSIF the beam strikes something bumpy [trees in pic above, but also rocks, hillside, undulations] THEN some of the waves are returned to be picked up by a detector on the satellite. Joan and co. have cross-referenced the terrestrial depth-post data with the satellite data and found a good enough match; so that's probably where they are going forward. For me this is a really nice mix of 19thC mapping & surveying with 21stC satellite magic. On the top of our hill in the Blackstairs is a rainfall monitor owned by Met Eireann: a copper funnel with a precise diameter over a collecting churn. One of the teenage girls in the last cottage up our bohereen was contracted by Met Eireann to yomp up the hill on a regular basis and measure the accumulated water since the last tally and throw it away so the churn was zeroed for the next slop of data. That is romantic but not efficient.

Why does it matter? Continuous data streaming of depth and area from groundwater flooding can help planners to determine where NOT to allow building to address Ireland's housing crisis. Because GW flooding involves landscape with no surface escape path for the flood-water, turloughs tend to hang around for a long time. Several families were unable to drive to-fro their homes for weeks after the "100-year floods" of Jan 2015. With climate change, you can bet your sweet bippy that 1000 year floods are now 100 year floods and 100 year floods will come more frequently. Cross-referencing the rainfall data with the flood-rise data allows a much wider demographic to plan their lives so that the car is on the right side of the turlough as if spreads across the bohereen . . . and go and buy a dinghy next time ALDI has one on Special.

Ghost Net

I just bought myself another set of garden secateurs €3 from ALDIDL. I think we have about a dozen knocking about the farrrrm in various states of usefulness. They take a hammering, not from pruning the roses but from filleting the tangles of ropes & buoys & nets & floats & hooks & pots which I find along the Waterford Coast. I don't need secateurs for boots, footballs, baby Crocs or driftwood: just a bag to carry them to the car-park., Indeed, The Beloved won't let me touch her secateurs because the fulcrum gets torqued out of true and they by-pass the rose-stems. Imagine having a job [above] detangling oceanic detritus and making an inventory of ghost nets in the Pacific Ocean. Ghost net is the technical term for hanks of orphan fishing gear lost at sea.

Boyan Slat is talking hot and hard about ghost nets, because microplastic [L in a sorting swirl in the Ocean Clean-up lab] is sooo yesterday. But more importantly, it's in recognition that it's easier to find and dispose of BIG chunks than the confetti that's left after the sun does it's photo-degradative work. "The French government offered a reward for ghost nets handed in to local coastguards along sections of the Normandy coast between 1980 and 1981. The project was abandoned when people vandalized nets to claim rewards, without retrieving anything at all from the shoreline or ocean [source]". Bounty incentives don't work for foxes or Tasmanian devils but have some success with lionfish. Boyan's key contribution is not to be disheartened by the vastness of the ocean and the low density of the the problem plastic. If you start somewhere with the biggest sweeper you can afford you're doing better than sitting on your sofa getting depressed about it and eating more crisps . . . out of  plastic. He has been pushing his boom broom [prev] solution but note that other people have different toolkits including microbial degradation of PET. His team has scaled to a 600m long sweep-net called Boomy McBoomface [woot! prev] made from HDPE = polythene. Here is that mother-if-all-booms being assembled in California.

They were concerned that their sampling methods were biasing the data to small bits. If you use only a children's dip-net, you'll never catch a salmon worth eating. So he went round the marinas or Hawaii and California and recruited 30 yachties to participate in a coordinated sweep across the North Pacific Gyre in the hope of seeing some trees in the woods. There are lots of Silicon Valley millionaires who have retired on their money and can do what they want with their time and their yacht.That was partly successful and they fished out several clots of ghost-net. But Boyish and enthusiastic Boyan is a classic example of TED-fodder and a money magnet. So they next leased a Lockheed C130 Hercules transport plane loaded it with short-wave IR sensors and LIDAR [prev on land from the air] and cameras and did a two sweep aerial reconnaissance of the Gyre. Integrating the two sorts of data, they now estimate that 50% of the 80,000 tonne mass of plastic [and below]could be ghost-nets . . . and so 'easily' recoverable. Well, easier than sieving out 2 trillion barely visible microplastic shards, while leaving the same-sized living plankton in place.

The Ocean Cleanup has a beautifully produced, informative and data-rich site.
The bold Boyan Slat is not the only one who is interested in sampling the oceans to assess the damage: data must precede solution! U Exeter have crowd-funded [they've exceeded their £20K target] an expedition to the Barents Sea in a romantic sailing ship. Barents Sea (not to be confused with Bering Sea on the other side of the Arctic) is the wet stuff between Svalbard [NO] and Novaya Zemlya Но́вая Земля́ [RU] not to be confused with Nova Zembla an island in the Canadian Arctic. Sails Against Plastic is not to be confused with Plastic Change a Danish sailing expedition to the Pacific. Confused? Me too!

I really hope that these parallel projects are talking to each other. I don't think I want them to merge to pool their resources yet. There is, of course, some duplication of effort but the positive aspect is that you have more creative heads working independently and banging those ideas up against each other to see which is best. Best for the Arctic may not be best for the Pacific, for starters.