Standard Referencing with GCP Overview

MultiPhoto provides two different modes of standard referencing:

• Full Reference 
  The 3D model is s transferred into a superior co-ordinate system by using known co-ordinates of externally surveyed GCP (at least three) by similarity transformation. 
• Single Point Mode 
  The 3D model is transferred to a co-ordinate system by using the co-ordinates of a single externally surveyed point (GCP) by similarity transformation. This mode is only available if the model is already referenced (EXIF GNSS positioning or imported camera co-ordinates). It allows to transfer the 3D model to a user defined co-ordinate system. 

User interface

To enter the referencing interface the button “Referencing” and “Ground Control Points” from the pull down menu has to be selected. 

The user interface Referencing of the MultiPhoto comprises the 3D viewer, the list of GCP and statistic parameters at the left hand side. On the right hand side it consists of a viewer showing the currently selected image for referencing and corresponding partner images.

1. 3D viewer                                                                  
2. GCP list
3. Viewer with selected image                                    
4. Partner images                                                         
5. Statistics

Features

Ground Control Points

• Full Reference - Mode for referencing the 3D model using three or more GCP
• Single Point - Mode for referencing the 3D model using a single GCP
• Co-ordinate system - Defines the co-ordinate system [generic or specified]
• Add GCP  - Adds a new GCP
• Load GCP From Text File  - Import co-ordinates from a text based file (“.csv”, “.txt”, “.dat”, “.prt”)
• Remove Selected GCP  - Removes the selected GCP
• Remove All GCP  - Removes all GCP
• Show Advanced Statistics  - Statistic extended with the reprojection and depth error 

View (2D Viewer)

• View full image  - Fits the size of the image to the size of the viewer
• Zoom to Target Region  -Zooms to the target region
• Manual Target Mode  - Activates manual targeting
• Automatic Target Mode  - Activates automatic targeting
• Sliders
  • 3D Marker Size - Changes the size of the target in the 3D viewer
  • 2D Crosshair Size - Changes the size of the crosshair in the 3D viewer
  • Target Region Radius - Defines the zoom (radius) to the target region
• Enable Image Filter - De/activates the image filter. 
  • Enabled filter: Images of the currently  clicked position in the 3D viewer are listed. 
  • Disabled filter: All images used for 3D model generation are listed.

Status

It provides a complete set of statistics, including Depth Error and Residuals, with maximum, mean, and standard deviation values. Additionally, the user receives information on the configuration of each individual GCP point (Baseline and Inliers), the current status of the referencing procedure, and guidance on the next step to perform.

Feedback on individual GCPs:

• Baseline: Indicates whether the selected measurements provide sufficient baseline
• Inliers: Indicates whether there are enough valid image measurements

Global Status is indicated using colour coding, with the following meanings:

• Red: The configuration contains errors and referencing cannot be performed. The status provides instructions on how to correct it.
• Orange: The configuration shows warnings. Referencing may be possible, but the data should be checked for validity first.
• Green: The configuration is valid and can be used for referencing.

General

• Save - References and saves the 3D model (“.jm3x”)
• Referencing - Choose another action: Inspect 3D Model 
• Export Data - Opens a dialog for selecting export possibilities; i.e. the reconstruction report (“.pdf”), ortho-photo (“.png”), GeoTIFF (“.tif”) and “.obj” export. See Chapter 13.
• Exit - Closes the MultiPhoto