KNOWLEDGE BASE

Processing with Pix4Dmapper

August 2016

Note: Pix4D has created an extensive repository of user guides and documentation as well as detailed how-to guides and webinars for all aspects of the software. Altavian strongly recommends utilizing the information provided on their support website to keep abrest of software updates and feature requirements: https://support.pix4d.com

For information regarding recommended computer hardware for Pix4Dmapper, click here to view the knowledge base article.

Software versions used for this article:
Pix4D Pro 2.2.22
Flight Visualizer 1.2.0.7
Payload Manager 1.1

Importing Flight Data

Pix4D features a user-friendly interface for importing flight data. Data from Fusion MP22 series payloads are directly supported in Pix4D. After specifying the desired images, Pix4D can automatically read the GPS information from the image EXIF tags and seamlessly process the data without any manual configuration. However, to fully utilize the advanced features of Fusion MP22 series payloads and increase potential processing accuracy, some manual configurations may be necessary.

Orientation Values

Inertial Navigation System (INS) values (referred to as ‘orientation’ in Pix4D) are only used for processing when the ‘Accurate Geolocation and Orientation’ calibration method is specified in Pix4D’s advanced Initial Processing settings menu. INS values are not directly importable in Pix4D using EXIF tags, therefore the dataset’s nav.txt file must be manually imported as a supported geolocation file. The closest configuration to Fusion MP22 series nav.txt files is a file format Pix4D calls ‘Latitude, Longitude, Altitude’.

In order to conform to this geolocation format, the TimeStamp values (second field) must be removed from the nav.txt file prior to importing. This may be done manually using a text editor or automatically by opening and editing the nav.txt file in Flight Visualizer. Once these values are removed, the nav.txt file is ready to import.

  1. On the Image Geolocation section, under Geolocation and Orientation, click From File…
  2. On the File Format drop down list, select Latitude, Longitude, Altitude
  3. Click Browse…
  4. On the Select Geolocation File pop-up, navigate to the image geolocation file, select it and click Open.
  5. On the Select Geolocation File pop-up, click OK.

Once loaded, the orientation values will appear in the Image Properties window.

Accuracy Definitions

When importing images with the Image Properties window, Pix4D generates default accuracy weights for horizontal and vertical GPS values. These default weights assume a low-accuracy GPS unit and therefore may yield poor processing performance. Altavian recommends to constrain these accuracy weights to match the accuracy specifications provided by the GPS unit manufacturer.

Values mentioned here are for X model Fusion MP22.

  1. In the Image Properties window, right-click one cell of the Accuracy Horz [m] column.
  2. Click Edit all Horz. Accuracies.
  3. Type 0.5.
  4. Hit the Enter key or click outside the cell.
  5. Right-click one cell of the Accuracy Vert [m] column.
  6. Click Edit all Vert. Accuracies.
  7. Type 1.5.
  8. Hit the Enter key or click outside the cell.

These values may be loaded automatically by concatenating them to the end of each line in the nav.txt file. In Flight Visualizer, navigate to Settings > Write GPS Accuracies for Pix4D and select the payload model.

Processing Color-Infrared (CIR) Data

Pix4D includes features to utilize color-infrared imagery for index calculations and precision agriculture solutions. In order to take advantage of these features, some manual configuration is necessary before processing.

Setting Central Wave Length & Band Weights

Before configuring bands in Pix4D, it is very important to understand the band order of the images that will be used for processing. By default, Fusion MP22 CIR payloads export images with a band order of R/G/NIR (Red/Green/Near-Infrared). If the bands have been flipped using Flight Visualizer, the band order will then be NIR/G/R. If wave length or weight values are specified for the wrong bands, resulting indices may produce poor results.

  1. In Pix4D’s Menu Bar, click Project > Image Properties Editor…
  2. In the Camera Model section under the Camera Model Name, click New.
  3. Enter a new name for the camera model.
  4. In the Image Properties Editor, under the section Selected Camera Model, click Edit.
  5. In the Camera Model section, click Edit.
  6. In the Camera Model Bands section, click Edit.
  7. In the Edit Camera Model Band Configuration window, click Edit.
  8. In the Edit Band Configuration window, configure the band names and weights as follows.

If the bands have NOT been flipped:

Name Central Wave Length [nm] Band Width [nm] Weight
 Red  660.0  0.0  0.0722
 Green  550.0  0.0  0.2126
 NIR  880.0  0.0  0.7152

 

If the bands have been flipped:

Name Central Wave Length [nm] Band Width [nm] Weight
 NIR  880.0  0.0  0.7152
 Green  550.0  0.0  0.2126
 Red  660.0  0.0  0.0722

 

  9. In the Edit Band Configuration window, click OK.
10. In the Edit Camera Model Band Configurations window, click OK.
11. In the Camera Model section underneath the Camera Model Name, click Save to Database.
12. In the Camera Model window, click OK.

Once complete, this newly-created camera model will be available in Pix4D’s camera database. For future projects using the same model Fusion MP22 CIR payload, selecting this model from the database will utilize these band configurations for processing.

 

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