Photogrammetry analysis - Site tests April 2023

Photogrammetry reconstruction

GPS & Photogrammetry Alignment (ENU)

GPS vs Photogrammetry Errors

Residuals and correlations

Site Photogrammetry reconstruction (April 2022)

Metashape parameters:

Depth Maps Quality: High
Model Quality: High

Liftoff point offsets

Equivalent distance deltas for Flights 4 through 11 all remain within 5 cm. A representative case is shown: Flight 8.

Photogrammetry reconstruction enhancement results:

The OpenCV photogrammetry reconstruction was enhanced with our own solution, which was based on the fact that the translation vector of the camera is known in 3D world-coordinate space (i.e., the drone coordinates measured by the GPS). This additional information allowed us to further constrain the photogrammetry problem and equations, resulting in a more robust solution that requires only a rough first estimation (± 5°) of the camera attitude to converge to the final camera angles (pitch, yaw, roll)

Flight 07 Photogrammetry reconstruction (Enhanced)

Target Coordinates

Target coordinates for Flight 07, total of 7 targets used for reconstruction: horizontal (left) and vertical (right)

Gaps in the curves mean that the target was not detected and the reconstruction was carried out using the remaining detected targets; this has no effect on the accuracy of the reconstruction, unless more than 2 targets are lost simultaneously.

Camera Attitude reconstruction

Jacknife Analysis

Flight 11 Photogrammetry Reconstruction (Enhanced)

Target Coordinates

Target coordinates for Flight 11, total of 6 targets used for reconstruction: horizontal (left) and vertical (right). Gaps in the curves mean that the target was not detected and the reconstruction was carried out using the remaining detected targets; this has no effect on the accuracy of the reconstruction, unless more than 2 targets are lost simultaneously.

Camera attitude reconstruction

Jacknife Analysis

Close up of the pitch, yaw, roll results of the jacknife analysis, carried out by removing 1 target (5 combinations in total), re-executing the enhanced photogrammetry reconstruction and calculating the standard deviation of each frame across the new sets. The standard deviation of each frame averaged over the full duration of the footage is shown on the top left section of the plot. The shaded section represents the region of uncertainty of each of the camera angles. The average standard deviation over the whole flight is shown for each plot.

Alt-az files with camera angles

An alt-az file that includes the source's pitch, yaw and roll angles has been generated based on the photogrammetry results for Flight 11. An extract of the file is shown below. This file can be found in the Zeus server in:

/storage/drone/field_tests/TOCO/20220429/Altaz_files/CLASS_altazpyr_05-oct/

Pitch, yaw and roll in Telescope reference frame

The pitch, yaw and roll angles obtained from OpenCV -and previously corrected using the GPS drone coordinates- were recomputed to represent the actual angles as observed from the telescope reference frame. This would allow, e.g., to obtain the actual roll angle of the source (and its polarization) as seen by the telescope and its detectors.

Pitch