Wednesday, 30 June 2010

Archeology in Aerial Photographs

We're pleased to announce a number of new texts now available on the NZETC website, including Kevin Jones' Ngā Tohuwhenua Mai Te Rangi: A New Zealand Archeology in Aerial Photographs, which the Department of Conservation has kindly allowed us to make available online.

Ngā Tohuwhenua Mai Te Rangi
Ngā Tohuwhenua Mai Te Rangi contains pictures of many important historic and pre-historic sites taken from the air, and shows how aerial photography can serve to improve our understanding of our geography.

Features such as the eel channels at Tangimate lagoon and the settlement patterns near the Whenuakura river are practically indiscernible from the ground, but become apparent from the air, and allow us to get a better understanding of land use (and abuse) of New Zealand since human settlement.

The gum-digging trenches on the Ahipara gumfields, created methodically by predominantly Croatian gum-diggers, demonstrate the scars that have been introduced into the landscape, as do the tailings from gold-dredging activities  near Cromwell.

Pre-European and European-era Pā are covered in detail, and the aerial photography allows us to appreciate features such as the ingeniously-constructed Tapui Pā, created by multiple ditches and banks on interlocking bends of the old course of the Te Arai River, near Manūtūke.

Images of fighting Pā such as Ruapekapeka  and Ohaeawai offer us the chance to more-easily visualise the settings of significant action during the Land Wars of the nineteenth century. As Jones describes:
Ruapekapeka, the last engagement in the northern phase of fighting in the New Zealand Wars, lies in hill country about 10 km south of the inner, estuarine reaches of the south-western Bay of Islands. The British soldiers used heavy cannon and howitzers with ball and shell against the pā; rockets were also used. Kawiti, the principal chief of the group occupying the pā, had designed the site with this in prospect. The interior defences of Ruapekapeka consisted of deep pits roofed over with timber and earth, 'bomb shelters', while the perimeter was defended by a heavily timbered palisade, flax-padding, and a continuous line of rectangular pits at the foot of an inner bank. Bastions and flanking angles were formed in the perimeter. These earthwork features all show clearly in the aerial photograph view.

In the fighting, the northern edge of the stockade was breached by cannon balls. As a result of the persistent cannon-fire, most of Kawiti's forces had been forced to camp in the rear of the defensive perimeter. On the advice of their Māori scouts, British troops attacked suddenly, on a Sunday morning. They found the fortification only lightly defended, and forced Kawiti himself to abandon it. The engagement was finished finally by the British forces occupying the pā against Kawiti's counter-attack from breastworks and the forest edge to the south. The position in which the British troops hac their cannon also survives as a shallow ditch and breast work. I photographed this site in February 1992, just after it fell into a light overcast. Luckily, there were distinct crop marks (browned grass) on the breastworks and their pattern shows clearly in the photograph.
Comparison of aerial images, such as the one provided by Jones of Ohaeawai, with a contemporary depiction of the scene of the battle, provide a better appreciation of the effect of the landscape on the outcome of the battle, and provide colour for passages such as James Cowan's account of the attack on Ohaeawai.

As well as the images of fighting Pā, aerial evidence of British and colonial fortifications such as the Kākāramea redoubt and Thacker's and Inman's redoubts — built during Cameron's Taranaki campaign of 1865-66 — give us the chance to appreciate the consequences in terms of fortifications of the imbalance between Maori (without significant artillery) and the European forces, who had support from land and sea-based artillery.

Comparison of images from different points in time allow us to determine the effects of development and erosion on the land, such as with the image of the Maketu peninsular, while images such as those of the storage pits near Paekākariki and the foundations of the Paremata barracks remind us that geographical evidence of history surrounds us, even if it is not always so obvious.

We've made these photographs available online at a higher resolution than we normally do with our texts, in order to let the viewer better see the detail captured. Although a thumbnail of the photograph is shown while reading through the text, repeated clicking on the image will bring up the full-resolution version.

As Jone's relates, the practice of taking aerial photographs involves getting a number of factors right, particularly the lighting which helps add relief to the scene.
To be seen effectively, then, New Zealand sites require strong oblique lighting conditions, typical of higher latitudes, winter, or early morning and late afternoon. Unfortunately, for perfectly valid reasons, it is typical practice in general aerial survey to take the photographs in summer and near midday, and archaeological features cannot be detected because of the lack of clear shadows and sometimes the effects of thistles or other seasonal vegetation growth. The problem is exacerbated in the far north where shadows almost disappear in summer at midday (because of the low latitude, 35°S).

The height at which the photograph is taken is very important in determining the size of the objects which can be seen on the ground: too far away and the site is imperceptible, too close and only the detail of a large site is visible. Archaeological sites vary in size: from a single spot where an artefact may have been found to a pā site that extends for more than a kilometre along a ridge. The plan of an individual storage pit may be as small as 2 by 1 m.
And perhaps another requisite for competent aerial photography is the possession of a good constitution:
High-angle oblique views require uncomfortably tight banks (steep turns) by the aeroplane to get a view unencumbered by its wheels.
Other recent additions
As well as Ngā Tohuwhenua Mai Te Rangi, we're pleased to also announce the following additions to the online collection of the New Zealand Electronic Text Centre:
Improved searchability
We're also been doing some work with access to and navigation around the NZETC's site, and we've introduced a much more comprehensive search interface that we think will help visitors to our site to more quickly be able to find the material they are interested in, and also enjoy the occasional fruits of serendipity.

For example, a search on Katherine Mansfield displays on the result page not only the works by and about Mansfield, but (by scrolling down) the user is able to see many of the photographs we have of, or connected with, Mansfield.

As always, we're interested in feedback about the texts that we make available online, and the experience that people have when accessing our collection.