One of the most obvious, but frequently overlooked, facts of archaeological investigation is that it is often a destructive process, and one that consumes a non-renewable resource. The awareness of this is particularly acute within the field of buildings archaeology, for unlike subsurface archaeology where there remains the constant possibility of an archaeological feature being unearthed; it is clear there is a dwindling inventory of pre-1900 structures. The economic factors such as development that drives the heritage sector are legislated for and administered by Heritage New Zealand Pouhere Taonga and private sector consultants, with the assessment of archaeological values largely determining how onerous the conditions for demolition and re-development will be. It is often tacitly understood that the commissioning of an archaeological report as a condition for an archaeological authority to demolish is sufficient mitigation for the irrevocable and destructive loss of New Zealand pre-1900 building stock. Whilst the rigor and detail of an archaeological report is essential, I would argue that the opportunity for providing the broader public with a more accessible and tangible way of engaging in New Zealand’s lost built environment has not yet been sufficiently met, with much of this information lost in the oblivion of ‘grey literature’. This situation is not helped by Heritage New Zealand’s practice of removing detailed information about listed buildings that have been demolished, further reducing the already scant amount of information about demolished heritage buildings available to the public.

In terms of visual representations one of the most common recording requirements is the production of two dimensional plans, sections, elevations, and other architectural details. Alongside photography this provides the primary visual record of a building. Advances in technology have reduced the time spent recording so that it is no longer necessary to record a building with a tape measure and graph paper as I was first taught, but the ways in which such information is shared and communicated still lag behind the building industry whose technical innovations are relied on so heavily by buildings archaeologists and heritage architects.

What I propose

 What I propose here is a publicly assessable 3D database of NZ heritage buildings. This would be a web-hosted platform where consultants would upload 3D data such as point clouds, photogrammetry, 2D elevations drawings – these could then be navigated zoomed and rotated, thus providing an accurate representation of our lost building stock for future generations.

What is photogrammetry and point cloud

 American Society for Photogrammetry and Remote Sensing states that photogrammetry is “the science and technology of  obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena” (aprs.org). A basic picture of a photogrammetry workflow would involve somebody with a camera or drone taking pictures of a building, importing the photo data into a computer program which would then process an exportable 3D model of the building that could then be hosted on-line. Point cloud is similar to photogrammetry and is usually captured with a 3D scanner. It provides a similar result but is generally a much faster recording process if somewhat more expensive due to the required equipment.

This is usually a three-step process that involves:

• The creation of a complex 3D model (very processor intensive) where the photos are extracted, and a texture rich model is generated.

• The initially complex model is the reduced to simplified mesh that enables the efficient use within a 3D viewing environment.

• The photos are then texture mapped onto a 3D mesh model.

A video link of both photogrammetry and point cloud models is provided below and should provide some indication of the attractiveness and ease of use of such media for the end user

What is stopping this happening?

 Like most problems in professional life, they can be divided into two categories: technical and bureaucratic.

The technological problems are manifold, this first issue would be that of hosting. There are a variety subscription services (free to the end user) where 3D models can be hosted. But the optimal solution would be to have a New Zealand-based platform and preferably a government subsidised one. But stable long-term platforms such as sketchfab.com with over 3,000,000 users worldwide, is a viable alternative in lieu of a New Zealand-based site. One argument for democratising this process on an open platform is that it would enable the public to 3D print models of demolished heritage building and bring them back to life in a tangible way.

The second technical issue is data security and avoiding obsolete formats, at the present time uncompressed TIFF is considered the gold standard for archiving digital photos and is all that would is required to reconstruct a 3D model in the case of data loss or eventual platform obsolescence.

The third issue is having personnel trained to capture adequate quality photography. A buildings archaeologist will often piggyback off architects and engineering consultants who will initially record a large site with a 3D scanner, sometimes with variable results. The below image is an ‘ortho-photo’ – a scale photographic elevation produced from point cloud data which can then be traced over in native CAD application to produce metric drawings. In this case several digital artefacts are reproduced in the image and will need to be corrected for by having recourse to photography.

The cost of implementing this is quite affordable and would only require a digital SLR and several hundred dollars for an appropriate software option. The use of affordable drone technology paired with HD cameras makes such a workflow flow a cost-effective option over standard building recording techniques due to the reduced recording time, and had the added benefit that scale 2D elevations (a normal requirement of most building reports) can easily be extracted at a later time.

In fact, it has been proven that by using appropriate methods of image capturing and by using robust software, the high expense of 3D laser scanning can be completely replaced.

On the bureaucratic side of the equation there are two major problems. Firstly, there is the question of who would take responsibility for administering a visual database. In the case of sites of international significance web-hosting is often site-specific, but on the other end of the spectrum there is a push for a more democratic and crowd sourced photogrammetry, especially for museums and curated collections. This makes obvious sense for cultural institutions that lack financial and human resources for digitisation work, and there is no reason why this could not be scaled up to include large objects such as built structures. Such a strategy has been used successfully in digitally reconstructing lost artefacts and monuments that have been destroyed during recent middle east conflict, and the idea is clearly relevant to potential natural disasters. I would go as far as to suggest that Category 1 heritage listed buildings should be pre-emptively 3D scanned, a process that could piggyback off engineering and condition reports that would use the same data sets. It would seem to me that this would be better implemented at a regional level through local body council regulations as a best practice for significant buildings scheduled on district plans. Christchurch is the prime example, where this loss of place is felt most acutely in an urban environment. Unfortunately too few buildings were scanned prior to demolition following the 2011 earthquake, even so many of these point clouds that could be easily converted to 3D models in the public domain remain largely neglected, and provide a valuable if unrecognized resource for digital heritage projects

But more broadly there needs to be a reassessment of how mitigation is understood for heritage management. The usual process when a developer attempts to demolish a heritage building is they have first proven that it is unfeasible to repair it for reuse or relocate it elsewhere, in which case assuming the assessment of values does not determine the building is of unique significance, it is then recorded prior to demolition. In the case of particularly significant buildings there is often additional monetary mitigation which might be, for example, directed to a local heritage fund. What I suggest is being lost in translation here is the understanding of mitigation relating to site specific intervention. The argument would go that if a structure is significant enough in terms archaeological values to warrant additional mitigation beyond the cost of commissioning a consultant’s report to the required standards, then these outputs should primarily be related to the production and preservation of site specific interpretations commensurate to the archaeological and historic heritage value of the building – 3D models are but one example of this. A non-virtual example of this often-missed opportunity is the too infrequent use of interpretative panelling, signage and other site-specific intervention that memorialize place. It should be noted that these two categories are not mutually exclusive, the overlapping of physical and virtual geographies is the next frontier in heritage management, with companies like http://www.virtimeplace.com/ producing apps that enable the viewer to walk through heritage sites and reconstruct a lost or degraded built environment based on an archaeologically accurate reconstruction. There is no reason why this technology could not be integrated with heritage signage and potentially broadened to incorporate other socially significant historical events where the connection between memory and the built environment has been disrupted. Overseas examples abound of the seamless integration of interpretive signage and multimedia that is incorporated into local body heritage planning policy, and should be understood as an aspect of forward looking and humane urban planning that takes some local responsibility for the inevitable consequences of development in New Zealand towns and cities.

What is being suggested here is really not that radical but requires a broadening of policy focus, one that takes further account of the stake the public has in its heritage. Such a shift would have the additional positive consequence of educating developers about the public interest in the management of heritage assets, one which is not merely a financial penalty, but a process of producing memory and cultural knowledge on a larger scale.

Michael Healey