Category Archives: SNH Compliant output

New SNH Visualisation Guidance Published (Lighting)

We were reminded today that the latest version of the SNH “Visual Representation of Wind Farms” came out of draft and was published last month (February 2017).

Version 2.2 of the guidance is an iterative update following the major release update (v2.0) in summer 2014 and the v2.1 revisions in December the same year.

A summary document of changes has been published as a separate download and provides practitioners and interested parties a rapid insight into the changes without the need to compare paragraph by paragraph.  The major change, impacting visual assessment and output for new developments is in paragraphs 174-177:

Turbine Lighting

For turbines in excess of 150m, the need to consult on new lighting visuals is now required.  Although future technical mitigation may help here, there is currently the recommendation to capture images at dusk and create a photomontage based on existing lighting (static streets, moving vehicles, other aviation lighting).
The visualisation should use photographs taken in low light conditions, preferably when other artificial lighting (such as street lights and lights on buildings) are on, to show how the wind farm lighting will look compared to the existing baseline at night.

NOT the Way to Visualise Wind Turbine Lighting!

Specifically the guidance makes reference to innovation in that SNH “encourage applicants to explore new techniques to do this, and emphasise the importance of early dialogue

We are looking for someone who will be creating night light visualisations to ensure that our upcoming night light features being built into VentusAR will work. If you have a project at the right stage, get in touch!


As we have experienced with the difference between animated wind turbines when compared against static imagery, there is a big difference between views of lighting where all the turbines are at a “maximum visibility” (worst case scenario) visibility and a more normalised situation with different wind directions and rotation occluding lights at certain times.  The more realistic effect can create a fairy lights twinkling effect, but is more representative.

For any clients, landscape assessors, planners or developers interested in exploring new ways to communicate, please contact us at

Wind Farm Impacts Study Published

Yesterday (2 July 2015) the ClimateXChange group published the results from a 2-year study into wind farm planning documentation. Specifically the report was designed to determine whether the “visual [and other] impacts predicted by wind farm developers in documentation submitted with their planning applications are consistent with the impacts experienced once the wind farm is operational.

The main report is a fairly weighty 190+ pages and available for download from ClimateXChange. Uniquely, the report has a steering group of government, professional and campaigner interests.

As the report focussed on the visual impact and interpretation of planning documentation, it is of particular interest to Linknode and the development of VentusAR and LVIA communication and engagement tool for planners, developers and communities alike.

The summary below is a very high level assessment of the visual components of the document.

We welcome this research as it clarifies the existing process and reassures the public that professional assessment is of a high quality. But also that process and proportionality are important. At Linknode we create technology to make visualisation and process more efficient and VentusAR now allows you to not only engage interactively, but to do so by following existing guidance. We are happy to discuss impact and implementations with any interested parties.

Study Area
Ten sites were used for case studies. These were filtered from a long-list and varied from large developments to significant single-turbine sites across Scotland. All applications had progressed through the planning process to construction and hence provided an ideal set of as-planned to as-built comparisons.

The ClimateXChange consultants reviewed all the internal (planning authority) and external (developer and consultees, including SNH) planning-stage documents for each application. Eight out of ten contained an Environmental Impact Assessment (EIA) which included a LVIA. Two smaller projects has no formal EIA, but did include landscape reports. Where four went to public inquiry, the reporters findings were also included.

Viewpoints were determined as appropriate for comparative assessment of documentation and for each study area visited twice (summer and winter) by a chartered landscape professional. When assessing viewpoints, the micro-siting (and lack of as-built consent documentation) made some comparisons difficult.

Additionally, a residential survey was carried out to a sample of households within 4km of sites. Six questions elicited answers on preference and for some of those site visits were carried out to assess significance. It was not clear from the document if questionnaire responses were self-selecting (which tends to promote a strong bias away from the normal).

Although disparate planning processes led to inconsistent documentation wrt visuals, GLVIA was generally applied with insignificant variations (fit for purpose).

It was not possible to ensure (through documentation review) that viewpoint coverage was representative and proportionate. In addition, it was not clear if the decision makers had actually visited viewpoints, or relied on printed materials (with some indication that reports were unread and only printed visuals consulted).

For the 25% of viewpoint assessments where the ClimateXChange professionals opinion differed from the original reporters, this was not put down to micro-siting alterations.

More detailed assessments of impacts on individual private views are not always required by the authorities and there is no standard methodology for carrying out such assessments.

Residential surveys show low correlation between residential impact and residents opinion on development. No before-and-after assessment was available.

Key Findings
The latest GLVIA (3, 2015) and SNH (2.1, 2015) guidance should be followed at all times.

A robust methodology for residential visual amenity and consistent implementation is required as consistent guidance.

Planning authorities should develop and agree pre-application and post-submission check lists for visual assessment.

Public consultation does not convey enough relevant information to attendees, and should include advice on micro-siting flexibility.

Pre-application, planning authorities should request a proportional number of viewpoints. And in addition make it clear at Scoping Opinion as to if/how residential visual amenity should be carried out.

At assessment and reporting, officials and reports should reference viewpoints visited and specific cases where their interpretation differs from the ES.

Micro-siting should be in line with documented constraints and aims in order that overall landscape objectives are retained in revisions. Final as-built location should be recorded as a matter of course (and monitored for accuracy by planning authorities).

Consultants Summary (Steering Group Statement)
The consultants suggested further improvements that could be made:
1. Guidance and methodology should be developed for residential visual impact surveys and
also, where appropriate, the overall impact on residential amenity due to the combined
visual, shadow flicker and noise effects of wind energy developments.
2. Checklists are needed for planners at scoping and post submission stages of an LVIA
(Landscape and Visual Impact Assessments) to ensure consistency and consideration of key
3. Consistent and clear reporting on the landscape and visual design objectives for a wind farm
should be set out in assessments.

Linknode Summary
The ClimateXChange report is a valuable tool in proving current, and guiding future planning governance.
The ability of new visualisation tools, in the office and field to provide low-cost, high accuracy proportional assessments of visuals means that developers, planners and communities should all get the opportunity to better understand applications and engage democratically with the planning process. Residential Visual Amenity Surveys should be an integral and essential part of the LVIA mix and VentusAR helps enable this rapidly and efficiently.

VentusAR v3.0 Released

We are delighted to announce that over the weekend, we released VentusAR v3.0 for Android and iPad (plus associated portal updates).

This is a significant feature release. VentusAR now has the added ability to create PDF output from images to comply with SNH guidance. Proudly, we estimate that photomontages can be created in VentusAR in just two hours – significantly shortening the time and expense for each one created. The aim is to make image assessment more inclusive and cheaper within the planning process.


We recommend you update to VentusAR v3.0 to take advantage of these new features.

For the mobile tablet, new features include:

  • Panorama viewer
  • Improved gallery sync
  • Public presentation mode

For the portal, major enhancements include:

  • Redesigned media tab to allow access to the new types of image (panorama, wireline, photomontage etc)
  • Enhanced PDF tab (allows PDFs to be managed more efficiently)
  • Enhanced viewpoint functions (allows viewpoints to be renamed / deleted)

Creating SNH compliant PDFs is a complicated business, and over the coming days and weeks we will document the process here on our blog. However if you would prefer a personal introduction to how the process works, please get in touch with us on 0141 559 6170 or email

Please see the full release notes for Android, iPad and the portal

Research on Trust in Visual Presentation Media

Or “How does the media used to convey a planned onshore wind development affect the understanding and belief in the visual representation?”


As is well known (in the UK at least) the visual impact assessment (VIA) component of the environmental statement is a critical component in planning for development, especially so in onshore wind.  Guidance has existed for many years based on the Landscape Institute’s GLVIA guidelines and focussed for onshore wind by Scottish Natural Heritage publications.  Neither are a legal framework for planning, but represent best practice and are de-facto standards for print production.

Digital technologies are becoming prevalent in all aspects of our life.  3D modelling, virtual, mixed and augmented reality are increasingly used as communication tools for planning (including Linknode’s VentusAR) where they can be more flexible, cheaper and dynamic. In 2014, Linknode utilised academic funding to create an independent assessment of paper and digital media.  The School of Psychology at The University of Glasgow undertook the research, headed by Dr David Simmons.

Existing Research

Recent research on GIS techniques for landscape and VIA assessment (WISERD, 2012) found that for digital landscape visualisation (LV):

  • Photomontages were rated highest overall in all in each of the four evaluation areas (ease of interpretation, landscape and visual impacts and perceived accuracy)
  • LV-based outputs were generally felt to lack the ‘realism’ of photomontages
  • Animated LV was rated more highly than static LV for assessing potential landscape and visual impacts
  • Problems with usability were a major issue with regard to dynamic LV-based visual tools, particularly navigation of the viewer position using the real-time LV model

In particular reference to onshore wind and landscape, Highland Council and The University of Stirling published results in 2012, leading to updates in the SNH guidelines.  This compared the effect of focal length on printed materials (not digital), however, it did not include figures on any observed statistical significance of the results.

SNH and LI (GLVIA) also publish and reference research extensively.

Psychology of Landscape and Visual Perception

At All-Energy 2014 in Aberdeen , we presented an introduction to the psychology of landscape visualisation called “Visualisation and Perceptions in Trust”.  A download link is available under the ‘documents’ section here.

This was the background to the trial that was designed and implemented by The University of Glasgow.

2014 Trial

Local, academic and professional people were invited to take part in a blind, naive trial – the real purpose was not exposed until the end (and thus had to be approved by the ethics committee).  Assessing a viewpoint from the University, participants were given a questionnaire and an ordered set of locations to attend.  Some locations were “at a viewpoint” with a clear aspect to the proposed turbine, and some were away – where there was no real-world view.  In both zones, a viewpoint visual (prepared to SNH standards by LDA Design), a static PDF of the visual and a tablet-based view based on a live, or near-live image with animation was presented.


The full results will be published in a peer-reviewed journal later this year for academic reference.  However, as part of the All-Energy Conference in Glasgow today (6 May 2015) we are highlighting key findings.  The slides below show how there is a consistent preference for digital technologies over paper and static digital.  The graphs show a median and IQR because averages are not appropriate statistics in this type of evaluation.

All Energy 2015 - A

It is up to the academics to answer the question such as Why?  But we do have observer comments that can clearly signpost us towards some of the reasons and one such eloquent description is below:

“the animated views were much more convincing and realistic of the visual impact of [the wind turbine], especially near window where I could easily visualise and compare this view both with and without the [wind turbine]”


Being “At the viewpoint” is important.
Observations showed that (using whatever medium), it is better assessed at the viewpoint, rather than away from the viewpoint.  This is important in comparing the input and influence of planning officials, elected members and committees when assessing a site.  The experience of users in different locations leads to different levels of belief and understanding of the project.

Tablet Medium was Preferred, Digital Static Not So
Observations showed that the tablet was rated “as good as” or “better” than other views for ALL tests (Ease of Use / Clarity / Trustworthiness / Information Shown / VIA Effectiveness).  Additionally, in overall preference, the tablet had the most trustworthy visuals and was referred, and the static digital view was the least preferred.

All Energy 2015 - B

It’s On / Under the Horizon

We all know the earth is not flat (well, apart from members of the Flat Earth Society).

Popular belief says that in the middle ages, sailors didn’t want to sail too far from their home port in case they fell off the edge of the world (though a quick bit of research on Wikipedia would suggest that this is a bit of a myth).

The earth is a complex shape, mathematically defined as a geoid (TL;TD – Wikipedia) or, more simply, it can be represented as an Oblate Spheroid (“oblate” because it is slightly oblong in appearance, “spheroid” because it is almost a sphere, but not quite) or rotated ellipsoid. VentusAR allows you to see far enough that we need to correct for curvature and ensure that the terrain shown in our 3D visualisations is not considered to be flat either.

There are a couple of good reasons for doing this: It makes our visualisations accurate when using a large viewing distance and it is required to be compliant with SNH standards for visualising windfarms. You’ll hear us talking alot about SNH standards for visualising windfarms over the next few weeks and months. We are in the process of making VentusAR capable of producing photomontages, wirelines and panoramas that are compliant with SNH Standards. So this is the first of several changes we’ve made to VentusAR to make the process of producing photomontages quicker (and therefore cheaper). Stay tuned to future blogs to hear what else we are doing.

Not correcting for earth curvature can make a huge difference to what can and cannot be seen. Over a viewing distance of 30km, a 60m turbine could drop completely out of sight. Consider the scene below: not correcting for earth curvature would suggest the tips of the turbine would be visible over the terrain. However because of earth curvature, the turbine tips would actually be hidden below the terrain.

No earth curvature correction: the turbine tip is visible over the terrain.

No earth curvature correction: the turbine tip is visible over the terrain.

Actual Model: The turbine tip is hidden behind the terrain

Actual Model: The turbine tip is hidden behind the terrain

SNH have produced guidance on how to include Earth Curvature and Atmospheric Refraction in your visualisations. Their requirements are published in their updated Visualising Windfarms guidance (v 2.1) – See Annex D on page 50. There are two corrections we need to make to calculate how much of a windfarm would be hidden behind the terrain: Earth Curvature and Atmospheric refraction.


Curvature is the most significant component that has an effect on how much of a windfarm is hidden behind the terrain. It is then a case of using Pythagoras theorem to calculate the height drop on the object. The equation used to calculate the vertical correction (the number of metres we should drop an object) due to earth curvature is shown below. [Note: there is an approximation in this formula, however unless you can see a distance approaching the radius of the earth – 6367km – it has a negligible effect on the maths].



  • h is the vertical correction in meters
  • c is the distance from viewer to object in meters
  • r is the radius of the earth in meters (6,367,000)


In reality, rays of light in sightlines are also curved downwards due to refraction of light through the earth atmosphere. This has the effect of allowing you to see approximately 15% beyond the expected horizon calculated using curvature alone. The standard formula used in surveying work takes into account refraction by adding a refraction coefficient (k) to the equation. For absolute accuracy, this coefficient should be measured at both ends of the line of sight – however this is not required for visualisation and visibility analysis so a reasonable average value of 0.075 has been used.

This makes our equation for working out vertical correction:



  • h is the vertical correction in meters
  • c is the distance from viewer to object in meters
  • r is the radius of the earth in meters (6,367,000).
  • k is the refraction co-efficient (0.075)


To give an idea of the effect of earth curvature and refraction on the visualisation produced, I’ve included a copy of the calculations as printed in the SNH guidance. To put this in context – if you were on a beach looking towards a wind turbine, over a distance of 30km a 60m wind turbine would not be visible because it is below the horizon.

Distance (c) Vertical Correction (h)
5km 1.7m
10km 6.7m
15km 15.0m
20km 26.7m
25km 41.7m
30km 60.1m

Implementation in MonoGame

It is well known that here at VentusAR, we use MonoGame to produce our visualisation screens. We have done two things to allow us to add Earth Curvature & Atmospheric Refraction to the VentusAR My View and Gallery: changed to using shaders and implemented shaders to include the vertical drop required.

What are Shaders

(This might get a bit technical – sorry)

3D Computer Graphics are based on a rendering pipeline. To convert a 3D representation of the world in computer memory, a series of steps are applied to the 3D data to produce something that can be displayed on the tablet screen. This rendering pipeline needs to be completed really quickly to ensure that the animation on the screen looks smooth – 60 times a second. Advances in computer graphic have given rise to powerful graphics cards to handle this processing. MonoGame allows developers to customize the processing that happens at different stages of this pipeline using shaders. As the shader functionality is very flexible, there are lots of possibilities of what developers can do with a shader: apply lighting to a 3D scene, change the texture on an object, change the position of an object.

(XNA / MonoGame pipeline from

(XNA / MonoGame pipeline from MSDN)

Summary: A shader is an operation that happens during the graphics rendering pipeline and can change the 3D model.

Earth Curvature Shader

We have written an Earth Curvature Shader that calculates the vertical drop (described above) based on the distance from the observer (mobile tablet) to the point in the 3D scene. As we chose to implement this as a shader, doing these calculations are quick: the visualisation screens can update 60 times a second to provide high quality animation and smooth motion. If it would help anyone, the implementation of the shader we are using can be found at VentusAR_TerrainShaderDiffuse.fx (please note: this is a .txt file, you will need to rename the shader file to be .fx)

Usage in VentusAR

We could never think of a time that users of VentusAR would not want to include Earth Curvature & Atmospheric refraction in their visualisations. So we have included it in the model every time the My View or Gallery is used (we don’t use it in the Fly Through, but as that evolves we may start to include it there). All visualisations produced with VentusAR 2.2 or later will include Earth Curvature and so be compliant with SNH guidelines.