50th Annual MeetingAssociation of Environmental and Engineering GeologistsLos Angeles, California
Thursday, September 27, 2007
The Benefits of Ground-BasedStereo Photography in Engineering Geology
PART 2 – A Brief Introduction to Processing Your Two Geopictures
Edmund Medley, PhD, PE, CEG, F.ASCEElizabeth Lincoln Mathieson, CEGSachiko Tanikawa
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 2
CAUTION!: Using anaglyph glasses
•YOU MAY NOT SEE STEREO IF YOU HAVE ONE STRONGER EYE
•JOG YOUR HEAD SLIGHTLY SIDE TO SIDE TO IMPROVE STEREO VIEW.
•BEWARE HEADACHES OR DIZZINESS: TAKE THE GLASSES OFF!!!!
left eye - red lens
Red/Cyan Anaglyph Glasses
(cyan = blue-green)
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 3
Checking Your 3-D Glasses
Pahoehoe lava, Hawaii Photo: Dr. E. Medley, 2006City Center, Oakland, CA Photo: Dr. E. Medley, 2007
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 4
From 2-D to 3-D -our eyes are
stereo viewers!
Why Stereo Photos Look 3-D
Graphic: after C. Snell, CEG
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 5
Left Camera
Right Camera
Cameras Mimic Eyesight
Graphic: after C. Snell, CEG
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 6
Ed Medley, Sachiko Tanikawa and Betsy Mathieson Photo: Dr. D. Zekkos
LEFT RIGHT
Most Important Tip:TAKE TWO GEOPICTURES!!
Part 1 lecture showed the value of taking two photos instead of one.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 7
“1-in-30 Rule” for Stereo Base
• Normally about 65 mm eye spacing
• Stereo base is the horizontal distance the camera moves
• Often 1/10 to 1/50 distance between lens to nearest object;
averaged as 1/30(e.g., distance 60 feet = move camera 2 feet horizontally)
• Variable stereo success within an image for features at
different distances from the camera
• Beware: If stereo base is too small: no stereo. If stereo base
is too large: exaggerated stereo.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 8
Medley’s Really Rough Rules
• Take photos with about 85% to 95% overlap (horizontally)
• “Cha-cha” for shots within a few tens of feet
• Use stereo-photo features of new digital cameras
(e.g., Canon®’s “stitch assist” mode)
• Rely on software to remove errors
• Take several photos or short digital movie
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 9
Stereo Base for Close Objects
Close Distance to Object
Depth of Field
Graphic: after C. Snell, CEG
Inches
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 10
Example Problem with Wide Stereo Base
Poor registration in very close foreground leads to fuzzy image (can be cropped) but also exaggerated stereo.
Pah
oeho
e La
va, H
awai
i
Pho
to: D
r. E
. Med
ley
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 11
Example Overlap for Close Views
Take LEFT photo first
For digital cameras, use LCD screen playback feature to help compose next frame.
Then take RIGHT image accordingly.
RIGHT
Left image overlap with right image > 90%
LEFT
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 12
Example Overlap for Close ViewsUse an identifiable object in both photos as a reference point.
LEFT? RIGHT?
+ =
Photos of rumpled fabric, with and without zipper.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 13
Photo Spacing for Far Objects
Far Distance to Object
Depth of Field
Graphic: after C. Snell, CEG
Feet
(mountains)
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 14
Example Overlap for Far Views
Don’t worry about vertical offsets, which can be removed in processing.BUT do not rotate camera – move it laterally.
Left image overlap with right image > 80%
LEFT RIGHT
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 15
HOWHOW do we see 3-D with our 2-D geopictures ?
Graphic: after C. Snell, CEG
Left Photo
Right Photo
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 16
Seeing 3-D Photographs
• Parallel and cross-eye “free viewing”• Stereoscopic viewers (single users)
– Portable– Format-specific– Can print images on paper
• Projection (audiences)– Slide projectors and LCD projectors– Red-cyan/red-blue anaglyph– Polarized
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 17
L
R
Stereoscopic Viewing
FUNDAMENTAL: MUST force left eye to look at left image and right eye to look at right image!! (or else headaches and confusion)
Graphic: after C. Snell, CEG
Screen/optical medium
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 18
Anaglyph (Red-Cyanor Red-Blue) Methodwith Glasses
Graphic: after C. Snell, CEG
L
R ProcessedImage
CombinationRed/Cyan
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 19
Sharing 3-D Photographs (on Paper)
• Parallel and Cross-Eye “free viewing”
– Not practical for reports or client use
• Stereoscopic viewers (single users)
– Can print images on paper
– As easy to produce as it is for mono photos
– Very effective in reports
– Cheap (<50¢) to expensive (>$10) viewers can be provided to clients/users
• CANNOT project for audiences
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 20
Projecting 3-D Photographs for Audience
• Use two 35-mm slide projectors or LCD projectors (need to use polarized filters and glasses)
• Use one LCD projector/monitor/plasma screen, etc., with red/cyan anaglyph images (need to use red/cyan glasses*) or other processed images
*Red/green and red/blue anaglyph images are also available and require corresponding colored glasses.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 21
Projector
AAnnaaggllyypphhiicc PPrroojjeeccttiioonnSc
reen
Left Image (red) andRight Image (cyan/green/blue) superimposed but slightly displaced.
Put your 3D glasses on!
The picture is blurry!!
Graphic: after C. Snell, CEG
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 22
Processing Images
• Do not need any processing if viewing prints with free stereo vision or stereoscope
• If you want to prepare images for computer review, reports or presentations, you must process them
• Can use many available cheap or free software programs such as Anaglyph Maker or PokeScope® or use any graphics program that will apply red and cyan layers
• Research web under “anaglyph software”• Reference: (both sites have much information on
stereovision. PokeScope® site also offers stereo viewing hardware.)– Anaglyph Maker
http://www.stereoeye.jp/software/index_e.html– Pokescope® http://www.pokescope.com
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Example - Processing Using PokeScope®
Open PokeScope®
Make sure “Stereo Mode” button is
depressed.
Make sure “Two File Input” button is
depressed.
All screen-captures were taken from PokeScope® Version 2.6.
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Open LEFT file Open RIGHT file
Example - Processing Using PokeScope®
Make sure “Side-by-Side” button is
depressed.
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Select common point on both images using cross-hair bars
(emphasized for example)
Click “Show Alignment” button
Example - Processing Using PokeScope®
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Click “Show Alignment” button again to generate aligned stereo pair
Example - Processing Using PokeScope®
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 27
Click on “Anaglyph Format” button to show
image as an aligned anaglyph image.
Example - Processing Using PokeScope®
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 28
ZOOM image to enlarge and review on-screen with anaglyph glasses
Example - Processing Using PokeScope®
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 29
Choose “Align” button to make fine adjustments using keyboard arrows (or bigger adjustments
using “Shift” key and arrows)
Example - Processing Using PokeScope®
Note: Use Left/Right keystrokes for adjustments in the X direction, Up/Down keystrokes for adjustments in the Y direction.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 30
SAVE AS anaglyph graphic file
Example - Processing Using PokeScope®
Choose desired image format (e.g., JPEG, TIFF, etc.)
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 31
SAVE AS stereo pair graphic file (or as processed individual LEFT and
RIGHT images)
Example - Processing Using PokeScope®
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 32
Fuzziness Due to Varying Stereo Base
Stereo image aligned to mid field of images, which results in uncomfortable anaglyph in foreground and background.
Can correct this by making separate images with different alignments. OK for analysis - not good for report or presentations.
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 33
Exaggerated Stereo
Near field exaggerated and distracting stereo. Solution? Crop it!
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 34
The Restless Sea and Other Movements
LEFT
RIGHT
Hanauma Bay area, Oahu Photo: Dr. E. Medley, 2007
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 35
Serendipitous Stereo
LEFT RIGHT
Too much stereo base and some rotation
Movement!- cars not in same positions in both images
Hanauma Bay area, Oahu Photo: Dr. E. Medley, 2007
two ordinary 2D panorama snapshots = unexpected, useful stereo
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 36
Stereo alignment optimized for middle
ground of image
Hanauma Bay area, Oahu Photo: Dr. E. Medley, 2007
...but stereo still OK for analysis.Serendipitous Stereo
E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 37
• Ground-based stereo images are cheap/easy to
take and process
• Take multiple pictures - digital cameras make it
easy and affordable
• Stereo images are invaluable where spatial
relationships are important
• Very effective for reports and presentations
Conclusions
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Think about your audience – they may not all be geologists or accustomed to readily seeing spatial relationships.
Conclusions
Photos: Anonymous Courtroom Bailiff, 2006
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Presentations are available at: http://www.geoengineer.org/stereophotos.html