Preprocessing of Agrowing QX1 images

The camera

Agrowing's modified Sony QX1 multi-spectral is a high-end agricultural multi-spectral camera, which is designed based on Agrowing’s patent pending lens technology.

Agrowing’s camera provides about 8 Mega Pixel resolution per color channel, with less than 1% distortion. Resoltion varies between 7.3 and 8.2 Mega Pixel depending on the settings. Agrowing’s camera has exchangeable NDVI and Red-Edge narrow bands lenses. The NDVI lens acquires 450nm, 550nm, 650nm and 850nm, and the Red-Edge lens acquires 450nm, 550nm, 710nm and 850nm.

Agrowing’s camera is based on a modified Sony ILCE QX1 camera. It weighs 335g (including battery and lens). Agrowing also developed a lightweight (40g) passive Nadir gimbal, which exploits the camera weight to keep its vertical position at all times, without consuming any battery power.

The combination of high resolution, narrow bands and low distortion with the possibility to exactly match the RGB and NIR data in Mavis makes Agrowing's camera a unique product in the market.

The camera records the RGB and NIR data on a single image sensor. Hence, the images must be preprocessed before any photogrammetrical analysis.

Preprocessing in Mavis

Agrowing processing in Mavis is run in batch mode. Simply click Batch and select a folder containing the images. However, several settings are required and can be tested after loading a single or multiple images with "Browse".

Settings

Crop This determines the size of the cropped area. "Strict" is recommended and extracts a smaller part compared to "normal" and "relaxed". This ensures that the darker part in the center of the images is excluded from the cropped sub-images.

Mount It is strongly recommended to mount the camera in portait mode. If it is mounted in landscape mode or some other rotation these should be set accordingly. It is also crucial for mission planning to use the correct settings of the sensor orientation. Agrowing provides *.xml files for the different GCS.

Format .JPG or .TIF can be selected as output formats. If .JPG is used the quality is set to 100%.

Copy Tags In case the Agrowing images are already geotagged "copy tags" should be selected. If georeferencing should be done in Mavis using an Ardupilot log file, this is not required.

Save composite When separating and matching the RGB and NIR images in Batch mode a composite image - such as NGB - can be saved in a separte folder as well.

Organisation of files

When processing the images in Batch mode Mavis generates two foldes

• RGB
• NGN

All further processing should be done in the RGB folder, which should be selected as the workspace in general preprocessing and 3D Mapping. The Digital Surface Model will then be based on the RGB data but two exactly overlapping orthomosaics will be generated. These can be further processing in the Vegetation Indices section of Mavis.

The composite images can be processed as well. This will be faster when generating the orthomosaics, but not provide an RGB orthomosaic. Hence, it is not recommended.

An AgrowingTimeTags.cam file will be written to the RGB folder. This contains the image trigger times and can be used when georeferencing the data to account for missing images. However, it is mandatory that all images on the SD-card belonging to the mission are processed.