Sun Shadow - Adverse Effects - Eliot Sinclair and Partners

ClientEliot Sinclair and PartnersLocationNew Zealand
ConsultantEliot Sinclair and PartnersContractorSam Cech

Sun Shadow Adverse Effects

Project Summary

The client applied to build a new house and access road, parking on a steep hillside. During the consent process, the owners of the neighbouring vacant section to the south suggested the proposal would have adverse effects on their property.

The task of the ESP team was to survey the property and evaluate the sun-shadow the proposal would cause on the existing environment.


  • Analyse a 3D model of the client property and neighbouring land, and measure the size of expected sun shadows at three different times of a day at maximum summer and winter sun positions.

  •  Calculate sun position and elevation at specified days (using sun almanacs and online software).

  • Cast digital sun rays on the 3D digital model and identify areas of shadow before and after development.

  • The team soon identified that the analysis would require a 3D model for the wider region due to the location of the hill section being on eastern elevation of Port Hills.

  • The impact of existing established large trees and neighbouring property to the North, as well as the existing legal road, had to be analysed prior testing the effects of the new development.


The ESP team selected 12d Model software for its ability to cast digital sun rays using the ViewShed option and 3D modelling tools.

The ViewShed option exclusively works on TINs, and the position of the Sun had to be over the same TIN. This was achieved by calculating the bearing and elevation of the sun at the specified dates and times of day and digital point was placed as the EYE position within ViewShed. It was necessary to model trees, buildings and parking areas, and include these in the same TIN.


12d Model ViewShed analysis generated section strings draped on the TIN, with segments coloured blue indicating shadows and segments coloured yellow indicating sun-shine.

The team manually checked the ViewShed results by generating cross sections, and prepared pairs of plans showing the pre- and post-development shadow effects.

The results from 12d Model ViewShed, and all their manual checks and verifications, convinced all parties 12d Model was the correct tool to use and the shadow results were accepted as the main argument to show there would be little impact caused on the land south of the subject property.

Due to the unconventional use of the ViewShed tool, some processes identified limitations within its core functionality. 12d Solutions was able to assist ESP by modifying the ViewShed to allow EYE positions to be as far away from the site as to imitate a SUN. As a result, they managed to reprocess all plans a few days later and meet their deadlines to present the results of this analysis in a hearing.

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