We talk a lot about Ljubljana Marshes, that 160 sq km marshy plain south of Ljubljana, and we have reasons for that. First, there is a lot of natural, archaeological, and historical moments to be found here (Iška moor nature reserve, prehistoric pile dwellings, Plecnik’s church), and second, the Marshes are flat and perfect for flying a kite…
Famous little church of St. Michael by Jozef Plecnik.
Ljubljana Marshes were a shallow lake in time of Neolithic and Bronze Age pile-dwellers. As the millenia passed it slowly silted up, turning into a large swamp with river Ljubljanica flowing through it, when suddenly – the Romans.
Area where the pile-dwellers built their pile dwellings 7.000 years ago.
As the Roman Empire expanded to the east in the beginning of the first century CE, gobbling up Noricum and Pannonia and Illyricum, the Romans first encountered our large marsh. And Romans being Romans, they went straight to work. They built a river port at the vauclusian springs of Ljubljanica near Vrhnika – Nauportus, they founded a city further up the river when the Marshes gave way to terra firma – Colonia Iulia Aemona, today’s Ljubljana – and they even moved a section of the whole river to bring it closer to the marble quarries of Podpec.
Moving rivers – the marvels of Roman engineering.
Romans weren’t really water people. They were the masters of land travel, they were the greatest road builders in history, criscrossing their conquests with (usually) straight lines going from town to town, from one Colonia to another, stretching for thousand of miles across the Empire, made for fast military movements, transport of goods and people – and, of course, all of them leading to Rome.
But these Marshes, they were something else. The wet, soft, swampy ground simply eats up anything you put on it. The ancient pile-dwellers knew that, so they built their huts on piles driven deep in the clay. But a Roman road – with intricate layers of rubble, slabs of stone, pebbles and gravel, topped up with smooth paving stones – going for miles? No way, not here.
Even today not many roads cross the Ljubljana Marshes.
And yet, the stubborn Romans persisted. They invented a fine wooden mesh that functioned as a pontoon, floating on the wet soil, on which they built a lighter layered road – one that withstood the Marshes. They constructed one from Ig in the south of the Marshes to Babna gorica and Lavrica on the eastern side – the first road was made, the Marshes were tamed. The road was so well constructed that a part of it is still used – you can drive on this Roman road today!
And even where this road is not a road anymore, it is still visible. For most of its course it’s a bit higher that the surrounding moors, so it can be seen on LIDAR data of the area:
LIDAR map with the Roman vicinal road marked. Courtesy of dr. Mija Toplicanec, Institute for the Protection of Cultural Heritage of Slovenia.
This road – for we know exactly where it is – is a perfect playground for our near-infrared camera testing. So we did the usual NIR, multispectral and visual kite aerial photos, flying the venerable Rokkaku in almost non-existing wind, under a hot summer sun, and here is what we got:
Roman road goes from left to right. Its typical trapezoidal cross section is still discernible. “Normal” photo, Canon A810.
Near-infrared photo of the road. NIR mod Pentax WG 10 with the 720 nm filter. The road is flatter than the surroundings and the plants grow poorly as the soil beneath is thinner.
Multispectral image of the road. Pentax WG-10 without the filter.
NDVI gradient map created from a NIR and a multispectral photo. NIR reflectivity of the plants on the road is reduced.
NDVI gradient map created from a NIR and a visual photo.
Animated GIF of the NDVI superimposed on the visual photo of the Roman road (marked with white lines). The difference in plant health (and NIR reflectance) is obvious.
Ortophoto and LIDAR map of the area we shoot.
As the tests go, this was a successful one. Now it’s time we put the camera and the kite on a real test – to discover something we don’t know yet …