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GCPCtrl can be used to assess the accuracy of a set of orientation from Check Points. The tool computes the image and ground reprojection error for each GCP. The tool is documented in DocMicMac.pdf ( Accuracy Control with GCPCtrl).


In photogrammetry, a standard method to control the accuracy of georeferencing result is to use couple of points called Check Points (CP). Check points, unlike Ground Control Points (GCPs), are used either to estimate the 3d similarity (GCPBascule) or for the compensation (Campari) on ground measurements. Residuals on check points allow to qualify the accuracy of the georeferencing result. If for a dataset, several ground measurements are available, a part may serve to perform georeferencing step (GCPBascule) while the rest of ground measurements can be used to qualify the accuracy and used as check points.


mm3d GCPCtrl -help

Mandatory unnamed args :

  • string :: {Full name (Dir+Pat)}
  • string :: {Orientation in}
  • string :: {Ground Control Points File}
  • string :: {Image Measurements File}

Named args :

  • [Name=CPI] bool :: {when Calib Per Image has to be used}
  • [Name=ShowU] bool :: {Show unused point (def=true)}


An example of the use of GCPCtrl:

mm3d GCPCtrl ".*JPG" Ori-RTL-Bascule CP.xml MesuresFinales-S2D.xml


— Ori-RTL-Bascule : are sets of orientations computed using Ground Control Points with (GCPBascule)

— CP.xml : are Check Points coordinates (not used to compute orientations of Ori-RTL-Bascule)

— MesuresFinales-S2D.xml : 2d Check Points coordinates

Residuals are used to estimate the accuracy. It is printed by GCPCtrl where D is the 3d residual and P is vector of deviations in axial components:


Ctrl 1 GCP-Bundle, D=0.00711013 P=[0.00157584,0.00215343,0.0065904]

Ctrl 2 GCP-Bundle, D=0.00213116 P=[-0.000812961,-7.10012e-05,0.00196873]

Ctrl 3 GCP-Bundle, D=0.00503373 P=[-0.00225834,0.000504016,0.00447037]

Ctrl 4 GCP-Bundle, D=0.013416 P=[-0.00209372,0.00171374,0.0131404]

Ctrl 5 GCP-Bundle, D=0.00778608 P=[-0.00129931,-0.000609828,-0.00765265]

Ctrl 6 GCP-Bundle, D=0.00432863 P=[-0.00166909,-0.00255773,-0.00306743]

Ctrl 7 GCP-Bundle, D=0.00536168 P=[0.00157972,-0.0050588,0.000812824]

Ctrl 8 GCP-Bundle, D=0.00493167 P=[-0.000829516,0.00146171,-0.00463645]

Ctrl 9 GCP-Bundle, D=0.00217372 P=[-0.000790291,-0.00131989,0.0015357]

============================= ERRROR MAX PTS FL ======================

|| Value=0.80781 for Cam=DSC08643.JPG and Pt=7 ; MoyErr=0.698737