photogrammetry as a research tool greg burgess derf november 2008

Photogrammetry as a research toolPhotogrammetry as a research tool

Greg BurgessGreg Burgess

DERF November 2008DERF November 2008

Measurement of direction from an imageMeasurement of direction from an image

Photographic determination of the Photographic determination of the coordinates of a pointcoordinates of a point

Fig

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Photographic determination of the Photographic determination of the coordinates of many pointscoordinates of many points

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Camera positionsCamera positions

Camera calibrationCamera calibration

Camera parameters to Camera parameters to determine:determine:

Principal distancePrincipal distance Principal point locationPrincipal point location Lens distortionsLens distortions

Archaeological photogrammetryArchaeological photogrammetryIm

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Mirror panel mould photogrammetryMirror panel mould photogrammetry

Mirror panel photogrammetryMirror panel photogrammetry

A very big dish…A very big dish…Im

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Image c

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SG4 jigSG4 jig

SG4 jigSG4 jig

Photo

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ston

Photo

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Photo

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Photo

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Jig with retro-reflective targetsJig with retro-reflective targets

Vision Measurement System (VMS)Vision Measurement System (VMS)

Problems…Problems…

Principal point instabilityPrincipal point instability

Principal point dependence on camera roll angle

-0.28

-0.26

-0.24

-0.22

-0.20

-0.18

0.05 0.10 0.15 0.20 0.25

PPx (mm)

PP

y (m

m)

-90˚ 0

90˚

Problems…Problems…

DewDew

FSJ4 1 Oct 2008 resultsFSJ4 1 Oct 2008 results

Estimated measurement accuracy:Estimated measurement accuracy:

σσx & x & σσy ≈ 0.5 mm, y ≈ 0.5 mm, σσz = 0.35 mmz = 0.35 mm

RMS height deviation of mounting points from the RMS height deviation of mounting points from the ideal paraboloid: ideal paraboloid: σσh = 0.56 mmh = 0.56 mm

Internal measurement precision: 1:230,000Internal measurement precision: 1:230,000

Pho

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