Fully verified photomontages

Recently, ACD was commissioned to undertake the production of fully verified photomontages, also known as Accurate Visual Representations (AVR) and Visually Verified Montages (VVM). We thought that it would be useful to share the process of how we prepare these.

The verified views are created using a combination of photography, survey data, 3D modelling and Computer-Generated Images (CGI). The photomontages produced are accurate, scaled images of what a scheme will potentially look like in the context of its proposed location. All verified views use precise, site-specific geographic data (including total survey station in the field) and 3D modelling to create the virtual view exactly as it would be seen. CGI is then used to place the development within the photomontage, making it a seamless transition between the reality of the photograph and the 3D model.

Taken from a specific viewpoint and using site-specific data, photomontages allow you to gauge the visual impact of the project before a single brick is laid. The methodologies are constantly evolving to be more sophisticated and detailed, with advice notes published by organisations such as the Landscape Institute detailing the current and correct procedures to follow. Visualisations are presented in 4 classifications: Type 1, Type 2, Type 3, and Type 4. Each category describes the level of render and detail applied. Type 1 visualisations provide a simple annotated viewpoint photograph. Type 2 are basic wireframe montages. Type 3 visualisations are ‘photorealistic’ photomontages, with Type 4 being verifiable. The higher the type classification, the greater the detail.

The first step is to take what is known as a ‘baseline’ photo. This involves undertaking a site visit and taking high-resolution, full-frame photos from pre-selected locations, that have ideally been agreed as part of a scoping exercise with the Local Planning Authority. This provides a current unaltered view of the site. For all verified views, it is important to use a fixed lens at a consistent focal length, that is in line with industry guidance.

Certain developments will require the use of panoramic photography to fit the whole scheme into one image. In this case, the numerous frames are manually stitched to the correct parallax point, allowing an approximate overlap of 20% at which point they are joined. A single viewpoint frame, usually centred on the site, is always supplied along with the panorama to show what a standard human would look like in the given situation.

During the site visit, a qualified surveyor will visit all the viewpoint locations and gather GPS readings to generate point data for objects within the baseline photos, this is undertaken simultaneously with the qualified landscape architect. Point data includes objects such as, lamp posts, railings, or corners of buildings. These ‘control points’ allow the views to be verified to +/- 20mm accuracy. The information collected is then cross-referenced with topographical surveys and OS data. The final point is used to visually align the virtual model with the original photograph in model space, before the photomontage creation.

Verified views are all about the development proposals; what the final build will look like within the existing context, therefore, modelling is key. It ensures that the design team’s intent is accurately understood and visualised. ACD create models of proposals either from scratch or from hand-drawn plans, AutoCAD drawings and Revit models. Using GPS topographic survey data, either gathered during the site visit or provided by the client, the model is positioned in the real-world model space occupied by the virtual cameras. Depending on the level of render and type classification, accurate architectural details are modelled onto the elevations, with proposed materials applied and accurately matched daylight and environments to illuminate the model.

The survey data and point cloud information are vital. They allow the control points to be aligned with the original photo to a great degree of accuracy. Without this information, the results are merely photomontages open to interpretation. Virtual cameras are set up in the modelling software which exactly matches the technical settings and physical locations of the site visit cameras. Focal lengths, ISO settings, aperture controls and exposure speeds are all determined with the GPS readings. The point data is visualised as cones in the model space and the virtual camera are aligned to match the baseline photos.

The final stage of the creation process is to merge the accurate camera-matched model with the corresponding baseline photo. Highly detailed renders are produced in the modelling software. These are then combined with the baseline photos in photo editing software.

To show the planting proposals over time, it can be useful to visualise how trees and shrubs may look in years to come, often between Year 0 and Year 15. The height and growth rate of the proposed vegetation is taken from industry data and provides an indication of potential vegetation cover or mitigation planting as it matures.

To fully understand the final verified views, all the information gathered and used in the creation process is compiled into a document, showing each viewpoint and each type classification output associated with it, ready for planning submission. This information includes camera settings, lens choice, times and dates, GPS coordinates and mapped camera locations, and reference photos of the camera and tripod in-situ.

If you would like more information regarding photomontages for your site, please contact ACD Environmental on 01666 825646 or emailing mail@acdenv.co.uk.