State estimation is a key ingredient in most robotic systems. Often, state estimation is performed using some form of least squares minimization. Basically, all error minimization procedures that work on real-world data use robust kernels as the standard way for dealing with outliers in the data. These kernels, however, are often hand-picked, sometimes in different combinations, and their parameters need to be tuned manually for a particular problem. In this letter, we propose the use of a generalized robust kernel family, which is automatically tuned based on the distribution of the residuals and includes the common m-estimators. We tested our adaptive kernel with two popular estimation problems in robotics, namely ICP and bundle adjustment. The experiments presented in this letter suggest that our approach provides higher robustness while avoiding a manual tuning of the kernel parameters.

Continuous crop monitoring is an important aspect of precision agriculture and requires the registration of sensor data over longer periods of time. Often, fields are monitored using cameras mounted on unmanned aerial vehicles (UAVs) but strong changes in the visual appearance of the growing crops and the field itself poses serious challenges to conventional image registration methods. In this paper, we present a method for registering images of agricultural fields taken by an UAV over the crop season and present a complete pipeline for computing temporally aligned 3D point clouds of the field. Our approach exploits the inherent geometry of the crop arrangement in the field, which remains mostly static over time. This allows us to register the images even in the presence of strong visual changes. To this end, we propose a scale-invariant, geometric feature descriptor that encodes the local plant arrangement geometry. The experiments suggest that we are able to register images taken over the crop season, including situations where matching with an off-the-shelf visual descriptor fails. We evaluate the accuracy of our matching system with respect to manually labeled ground truth. We furthermore illustrate that the reconstructed 3D models are qualitatively correct and the registration results allow for monitoring growth parameters at a per plant level.

In grapevine research the acquisition of phenotypic data is largely restricted to the field due to its perennial nature and size. The methodologies used to assess morphological traits and phenology are mainly limited to visual scoring. Some measurements for biotic and abiotic stress, as well as for quality assessments, are done by invasive measures. The new evolving sensor technologies provide the opportunity to perform non-destructive evaluations of phenotypic traits using different field phenotyping platforms. One of the biggest technical challenges for field phenotyping of grapevines are the varying light conditions and the background. In the present study the Phenoliner is presented, which represents a novel type of a robust field phenotyping platform. The vehicle is based on a grape harvester following the concept of a moveable tunnel. The tunnel it is equipped with different sensor systems (RGB and NIR camera system, hyperspectral camera, RTK-GPS, orientation sensor) and an artificial broadband light source. It is independent from external light conditions and in combination with artificial background, the Phenoliner enables standardised acquisition of high-quality, geo-referenced sensor data.

Monitoring plants and fruits is important in modern agriculture, with applications ranging from high-throughput phenotyping to autonomous harvesting. Obtaining highly accurate 3D measurements under real agricultural conditions is a challenging task. In this letter, we address the problem of estimating the 3D shape of fruits when only a partial view is available. We propose a pipeline that exploits high-resolution 3D data in the learning phase but only requires a single RGB-D frame to predict the 3D shape of a complete fruit during operation. To achieve this, we first learn a latent space of potential fruit appearances that we can decode into an SDF volume. With the pretrained, frozen decoder, we subsequently learn an encoder that can produce meaningful latent vectors from a single RGB-D frame. The experiments presented in this letter suggest that our approach can predict the 3D shape of whole fruits online, needing only 4 ms for inference. We evaluate our approach in controlled environments and illustrate its deployment in greenhouses without modifications.

Precise scene understanding is key for most robot monitoring and intervention tasks in agriculture. In this work we present PAg-NeRF which is a novel NeRF-based system that enables 3D panoptic scene understanding. Our representation is trained using an image sequence with noisy robot odometry poses and automatic panoptic predictions with inconsistent IDs between frames. Despite this noisy input, our system is able to output scene geometry, photo-realistic renders and 3D consistent panoptic representations with consistent instance IDs. We evaluate this novel system in a very challenging horticultural scenario and in doing so demonstrate an end-to-end trainable system that can make use of noisy robot poses rather than precise poses that have to be pre-calculated. Compared to a baseline approach the peak signal to noise ratio is improved from 21.34 dB to 23.37 dB while the panoptic quality improves from 56.65% to 70.08%. Furthermore, our approach is faster and can be tuned to improve inference time by more than a factor of 2 while being memory efficient with approximately 12 times fewer parameters.

Precision farming robots offer the potential to reduce the amount of used agrochemicals through targeted interventions and thus are a promising step towards sustainable agriculture. A prerequisite for such systems is a robust plant classification system that can identify crops and weeds in various agricultural fields. Most vision-based systems train convolutional neural networks (CNNs) on a given dataset, i.e., the source domain, to perform semantic segmentation of images. However, deploying these models on unseen fields, i.e., in the target domain, often shows a low generalization capability. Enhancing the generalization capability of CNNs is critical to increasing their performance on target domains with different operational conditions. In this letter, we present a domain generalized semantic segmentation approach for robust crop and weed detection by effectively extending and diversifying the source domain to achieve high performance across different agricultural field conditions. We propose to leverage unlabeled images captured from various agricultural fields during training in a two-step framework. First, we suggest a method to automatically compute sparse annotations and use them to present the model more plant varieties and growth stages to enhance its generalization capability. Among others, we exploit unlabeled images from fields containing crops sown in rows. Second, we propose a style transfer method that renders the source domain images in the style of images from various fields to achieve increased diversification. We conduct extensive experiments and show that we achieve superior performance in crop-weed segmentation across various fields compared to state-of-the-art methods.