Sun Shadow Adverse Effects
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
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.
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
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
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