What is Pix4D? What Products does it generate?
Pix4D is a popular software that is used to generate point clouds from UAS data. It utilizes GCPs and photgrammetry to create point clouds and DSMs.
Why is it so integral to UAS data processing?
Pix4D is so integral in processing UAS data because it produces DSMs from simple pictures, this DSM is the baseline for all other processing.
Assignment Methods:
The first step in processing an image in Pix4D is initial processing of the images. This will report a quality report that is integral in the accuracy of further processing. You perform ONLY the initial processing first because the next two steps (point cloud and orthomosaic) take a long time to process, so if your initial report comes back with bad data, you do not have to waste time processing the next two steps. Figure 1 shows an example of a quality report. Take note of the processing time.
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| Figure 1. Initial Processing Quality Report |
Some of the things the quality report checks for is georeferencing, pixel matching, and camera settings. After confirming your data is correct in the quality report, you can continue with point cloud processing. Figure 2 shows the final point cloud.
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| Figure 2. Final Point Cloud
When dealing with Pix4D data, the number out outputs can become confusing. That is why it important to have a proper file system. An ideal system would have 3 separate folders for collection, processing, analysis with metadata placed in the master folder. Figure 3 shows an example of this file naming convention.
After the DSM has been created from the point cloud, the next step was to create a deliverable product that was easy to consume for the customer. This was done by creating a video of the actual DSM itself. To do this, you needed to chose the trajectory point in the DSM, figure 4 shows the video trajectory points that were created. An actual video of the DSM can be found in the figures page of this portfolio.
The DSM created in this assignment is similar to the one used in Lab #3, the difference is that this DSM did not utilize GCPs. This allowed for not accurate elevation values as shown in figure 5.
Assignment Conclusions:
Pix4D is important in processing UAS data because it takes the pictures that are taken by a drone, and processes them into manipulated DSMs and point clouds. this, however, takes alot of time to get accurate results if trying to process a large area, for example, if trying to process a folder of 6000+ images, it could take upwards of 24 hours depending of how accurate you want the DSM.
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