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50 th Annual Meeting Association of Environmental and Engineering Geologists Los Angeles, California Thursday, September 27, 2007 The Benefits of Ground-Based Stereo Photography in Engineering Geology PART 2 – A Brief Introduction to Processing Your Two Geopictures Edmund Medley, PhD, PE, CEG, F.ASCE Elizabeth Lincoln Mathieson, CEG Sachiko Tanikawa

The Benefits of Ground-Based Stereo Photography in ... · The Benefits of Ground-Based Stereo Photography in Engineering Geology ... but also exaggerated stereo. Pahoehoe Lava, Hawaii

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Page 1: The Benefits of Ground-Based Stereo Photography in ... · The Benefits of Ground-Based Stereo Photography in Engineering Geology ... but also exaggerated stereo. Pahoehoe Lava, Hawaii

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

Page 2: The Benefits of Ground-Based Stereo Photography in ... · The Benefits of Ground-Based Stereo Photography in Engineering Geology ... but also exaggerated stereo. Pahoehoe Lava, Hawaii

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)

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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

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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

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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 5

Left Camera

Right Camera

Cameras Mimic Eyesight

Graphic: after C. Snell, CEG

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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.

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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.

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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

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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

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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

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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

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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.

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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)

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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

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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

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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

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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

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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

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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

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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.

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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

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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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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 23

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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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 24

Open LEFT file Open RIGHT file

Example - Processing Using PokeScope®

Make sure “Side-by-Side” button is

depressed.

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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 25

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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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 26

Click “Show Alignment” button again to generate aligned stereo pair

Example - Processing Using PokeScope®

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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®

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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®

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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.

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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.)

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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®

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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.

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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 33

Exaggerated Stereo

Near field exaggerated and distracting stereo. Solution? Crop it!

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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

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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

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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

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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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E. Medley, E. Mathieson and S. Tanikawa, AEG Los Angeles, 2007 38

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