Visual Representation of
Windfarms
Technical Session 2:
Getting the pictures out of the camera
(and what to do with them)
Ian McAulay
[email protected]
SNH Requirements
For each viewpoint…
•
•
•
•
•
90°-360° baseline photo
90°-360° cumulative wireline
‘75mm’ wireline (53.5° wide)
‘75mm’ photomontage (53.5° wide)
Panoramic JPEG photomontage for digital
viewer
• ‘75mm’ photomontage (27° wide)
Different projections
Cylindrical Projection:
• 90°-360° baseline photo
• 90°-360° cumulative wireline
• Panoramic JPEG photomontage for digital viewer
Planar Projection:
• ‘75mm’ wireline (53.5° wide)
• ‘75mm’ photomontage (53.5° wide)
• ‘75mm’ photomontage (27° wide)
Planar Projection
Single frame
Planar Projection
Wider field of view but still planar
Planar Projection
Multiple frames
Cylindrical Projection
Reconstructing the Perspective
Reconstructing the Perspective
Workflow
• This is the way Envision do it.
• It’s not the only way you can do it.
• These are not the only tools you can use.
Workflow
DTM data
Photo
parameters
Windfarm
model
Photos
Panoramic
wireline
Rendering
Photo
panorama
Layered
Photoshop
file
53.5°
Planar
wireline
90°
Cumulative
wireline
90°
Baseline
photo
Panoramic
JPEG
montage
53.5°
Planar
montage
27°
Planar
montage
Panoramic Wireline
• Provides geometric framework for matching
photomontage
• Envision usually work with 180° or 360°
panoramas
• Envision standard resolution is 36,000 x 3000
pixels
Photo Panorama
• Constructed semi-automatically from
separate photo frames
• Many software solutions for stitching
• Envision have used PTGui and Hugin
successfully
Stitching Software
• Must allow inspection/correction of control
points
• Must blend frames smoothly without
obvious blurring
• Must support wide output images
• Must deliver geometrically reliable results
Reprojecting
Single frame as taken
Reprojecting
Single frame reprojected to cylindrical
Reprojecting
• All panorama stitching software
reprojects the individual frames as part
of the stitching process
• Better software also corrects lens
distortion
• Hugin can also act as a standalone
reprojector
Stitching (PTGui)
Control Points
Control Points
Matching
• Wireline is the geometrical framework for
matching
• Adjust photo to fit wireline (not the other
way round)
• Use terrain and as many reference objects
as you need
• Reference objects may be well away from
main direction of view
Matching
Matching
Matching
• Terrain provides a good reference for
matching in upland areas
• Terrain is useless in flat areas!
• Identify likely reference objects in the
view
• Find coordinates for them (Google Earth
is good for this)
• Model them as additional objects in the
wireline
Matching
• If it’s impossible to get a good match on
all the reference objects at one,
something may have gone wrong
• Check that the viewpoint coordinates are
right (transposed digits?)
• See if the coordinates look reasonable on
a map
• Find the viewpoint on Google Earth and
double check that way
Reality Bites…
YOUR CAMERA IS NOT LEVEL!
Levelling/Straightening
• Minor levelling errors manifest as curved
panoramas
• Unavoidable within limits of accuracy of
equipment
• Fix in Photoshop!
Straightening
Straightening
Rendering
• Match between wireline and photo
establishes and verifies perspective
parameters
• Parameters can go straight into rendering
software to produce shaded image of
windfarm for montaging
• Envision variously uses POVray, V-Ray and
Sketchup with final tweaks in Photoshop
Montaging
Montaging
Montaging
Finished Images
•
•
•
•
•
90°-360° baseline photo
90°-360° cumulative wireline
‘75mm’ wireline (53.5° wide)
‘75mm’ photomontage (53.5° wide)
Panoramic JPEG photomontage for digital
viewer
• ‘75mm’ photomontage (27° wide)
Finished Images
90°-360° Baseline photo:
• Crop from photo layer of layered file
• More than one if more than 90° needed
Finished Images
90°-360° Cumulative wireline:
• Crop from wireline layer of layered file
• More than one if more than 90° needed
Finished Images
‘75mm’ wireline (53.5° wide):
• Generate separately as planar projection
• (Reprojecting line drawings makes them
slightly blurry)
Finished Images
‘75mm’ photomontage (53.5° wide):
• Extract from merged montage and photo
layers of layered file
• Reproject to planar using Hugin
Finished Images
Panoramic JPEG photomontage for
digital viewer:
• Extract from merged montage and photo
layers of layered file
• Crop to size
Finished Images
‘75mm’ photomontage (27° wide):
• Crop down from 53.5° photomontage
Page Layout
• Image and page sizes are fully specified
by SNH
• The Viewpoint Pack is A3
• All other visualisation pages are ‘half A1’,
841 x 297 mm
Page Layout
90°-360° baseline photo
90°-360° cumulative wireline
• Images 820 x 130 mm
• Page ‘half A1’, 841 x 297 mm
Page Layout
‘75mm’ wireline (53.5° wide)
• Image 820 x 260 mm
• Page ‘half A1’, 841 x 297 mm
Page Layout
‘75mm’ photomontage (53.5° wide)
• Image 820 x 260 mm
• Page ‘half A1’, 841 x 297 mm
Page Layout
‘75mm’ photomontage (27° wide)
• (For viewpoint pack)
• Image 390 x 260 mm
• Page A3 (420 x 297 mm)
Printing
• Minimum image resolution 300 ppi (pixels
per inch)
• Check sample prints for colour balance
and legibility
• (Slight over-sharpening of images is
sometimes required for printing)