photographic obstruction mapping/media/com/velux days... · halioglass.com 2 daylight and views are...

Photographic

Obstruction

MappingAndy McNeil,

Kinestral Technologies Inc.

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▪ Daylight and Views are widely desired• Daylight is the most desirable benefit employers can offer to employees

• Homes with ample daylight are more valuable than those with less

▪ Humans are terrible at manual control of shading• We are triggered by glare

• The un-trigger is ambiguous and rarely noticed

▪ Shades stay down far longer than needed• Daylight is squandered

• Views are blocked

Daylight is awesome, manual shades are not.

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▪ Automation needs to be cost effective at small scale• € / window for 10 windows vs. 1,000 windows

▪ Automation needs to do the ‘right thing’ all the time.• 95% correct = Wrong 2 hours per work week

• 99.5% correct = Wrong 12 minutes per work week

▪ One thing that needs to be done right:

Don’t activate shading when the widow is in a shadow!

Automated control is the way forward

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Obstructions…

▪ Cast shadows on windows

• Neighboring buildings

• Static Shading devices, eg.

overhangs, fins

• Mountains / Hills

• Trees (?)

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Currently accounted for by

ray-tracing CAD models

▪ Model preparation can be time consuming and costly

▪ CAD model availability is spotty.• Often limited to building outlines

• Height needs to be estimated

▪ Errors are often baked into the schedule, and difficult to diagnose and correct.

▪ Substantial up-charge is passed on to the customer

• Economical for large projects

• Not practical for small projects

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▪ Collect obstruction information

onsite with calibrated camera.

▪ Remap pixes to angular

coordinates

▪ Identify sky vs. obstruction

▪ Query with sun position

Photographic Obstruction Maps

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Calibrated Camera (Prototype)

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▪ 180° Fisheye lens

▪ Black shroud for

positioning

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Accelerometer

▪ Accelerometer to correct for crooked hand

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Lens distortion

▪ Angular calibration to correct for lens

distortion

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▪ X-axis:• azimuth angle

• projected into horizontal plane

▪ Y-axis:• profile angle

• projected into vertical plane

▪ Lines that are orthonormal to the direction of view are straight lines in the orthonormal projection.

‘Orthonormal Pseudocylindrical’ Projection

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Image Plane0°

+90°

-90°-90° 0° +90°

Azimuth

Pro

file

Angle

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‘Orthonormal Pseudocylindrical’ Projection

Equirectangular Projection Orthonormal Projection

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Re-projection

▪ Fisheye to orthonormal projection

▪ Straight Line = Pleasant!

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Equirectangular…

Equirectangular

▪ Not straight line = awkward

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Trace Visible Sky

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Now it’s an angular obstruction map!

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Validation

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▪ Predicted time:

7:39

▪ Actual time:

7:42

▪ Error of 3 minutes, 0.4°

Sun begins to shine on the window

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▪ Predicted time:

11:06

▪ Actual time:

11:03

▪ Error of 3 minutes, 0.7°

Sun ceases to shine on the window

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▪ A calibrated camera can be used to generate angular maps of exterior

obstructions

▪ The maps are thought to be accurate to within 1°, though validation is

ongoing.

▪ This method is economical for small projects.

Summary

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Example:

Paris Hotel

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Example:

New York City Office

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Example:

Los Angeles Office

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