Assessing Biodiversity in Boreal Forests with UAV-Based Photogrammetric Point Clouds and Hyperspectral Imaging

Forests are the most diverse terrestrial ecosystems and their biological diversity includes trees, but also other plants, animals, and micro-organisms. One-third of the forested land is in boreal zone; therefore, changes in biological diversity in boreal forests can shape biodiversity, even at global scale. Several forest attributes, including size variability, amount of dead wood, and tree species richness, can be applied in assessing biodiversity of a forest ecosystem. Remote sensing offers complimentary tool for traditional field measurements in mapping and monitoring forest biodiversity. Recent development of small unmanned aerial vehicles (UAVs) enable the detailed characterization of forest ecosystems through providing data with high spatial but also temporal resolution at reasonable costs. The objective here is to deepen the knowledge about assessment of plot-level biodiversity indicators in boreal forests with hyperspectral imagery and photogrammetric point clouds from a UAV. We applied individual tree crown approach (ITC) and semi-individual tree crown approach (semi-ITC) in estimating plot-level biodiversity indicators. Structural metrics from the photogrammetric point clouds were used together with either spectral features or vegetation indices derived from hyperspectral imagery. Biodiversity indicators like the amount of dead wood and species richness were mainly underestimated with UAV-based hyperspectral imagery and photogrammetric point clouds. Indicators of structural variability (i.e., standard deviation in diameter-at-breast height and tree height) were the most accurately estimated biodiversity indicators with relative RMSE between 24.4% and 29.3% with semi-ITC. The largest relative errors occurred for predicting deciduous trees (especially aspen and alder), partly due to their small amount within the study area. Thus, especially the structural diversity was reliably predicted by integrating the three-dimensional and spectral datasets of UAV-based point clouds and hyperspectral imaging, and can therefore be further utilized in ecological studies, such as biodiversity monitoring

Cetuximab continuation after first progression in metastatic colorectal cancer (CAPRI-GOIM): A randomized phase II trial of FOLFOX plus cetuximab versus FOLFOX

Background: Cetuximab plus chemotherapy is a first-line treatment option in metastatic KRAS and NRAS wild-type colorectal cancer (CRC) patients. No data are currently available on continuing anti-epidermal growth factor receptor (EGFR) therapy beyond progression. Patients and methods: We did this open-label, 1:1 randomized phase II trial at 25 hospitals in Italy to evaluate the efficacy of cetuximab plus 5-fluorouracil, folinic acid and oxaliplatin (FOLFOX) as second-line treatment of KRAS exon 2 wild-type metastatic CRC patients treated in first line with 5-fluorouracil, folinic acid and irinotecan (FOLFIRI) plus cetuximab. Patients received FOLFOX plus cetuximab (arm A) or FOLFOX (arm B). Primary end point was progressionfree survival (PFS). Tumour tissues were assessed by next-generation sequencing (NGS). This report is the final analysis. Results: Between 1 February 2010 and 28 September 2014, 153 patients were randomized (74 in arm A and 79 in arm B). Median PFS was 6.4 [95% confidence interval (CI) 4.7-8.0] versus 4.5 months (95% CI 3.3-5.7); [hazard ratio (HR), 0.81; 95% CI 0.58-1.12; P = 0.19], respectively. NGS was performed in 117/153 (76.5%) cases; 66/117 patients (34 in arm A and 32 in arm B) had KRAS, NRAS, BRAF and PIK3CA wild-type tumours. For these patients, PFS was longer in the FOLFOX plus cetuximab arm [median 6.9 (95% CI 5.5-8.2) versus 5.3 months (95% CI 3.7-6.9); HR, 0.56 (95% CI 0.33-0.94); P = 0.025]. There was a trend in better overall survival: median 23.7 [(95% CI 19.4-28.0) versus 19.8 months (95% CI 14.9-24.7); HR, 0.57 (95% CI 0.32-1.02); P = 0.056]. Conclusions: Continuing cetuximab treatment in combination with chemotherapy is of potential therapeutic efficacy in molecularly selected patients and should be validated in randomized phase III trials

Reconstruction of Cylindrical Surfaces Using Digital Image Correlation

A technique for the reconstruction of cylindrical surfaces using optical images with an extension of least squares matching is presented. This technique is based on stereo-image acquisition of a cylindrical object, and it involves displacing the camera following the object length. The basic concept behind this technique is that variations in the camera viewpoint over a cylindrical object produce perspective effects similar to a conic section in an image sequence. Such parallax changes are continuous and can be modelled by a second-order function, which is combined with an adaptive least squares matching (ALSM) for the 3D object reconstruction. Using this concept, a photogrammetric intersection with only two image patches can be used to model a cylindrical object with high accuracy. Experiments were conducted with a cylinder on a panel with coded targets to assess the 3D reconstruction accuracy. The accuracy assessment was based on a comparison between the estimated diameter and the diameter directly measured over the cylinder. The difference between the diameters indicated an accuracy of 1/10 mm, and the cylindrical surface was entirely reconstructed

Automatic Orientation of Multi-Scale Terrestrial Images for 3D Reconstruction

Image orientation requires ground control as a source of information for both indirect estimation and quality assessment to guarantee the accuracy of the photogrammetric processes. However, the orientation still depends on interactive measurements to locate the control entities over the images. This paper presents an automatic technique used to generate 3D control points from vertical panoramic terrestrial images. The technique uses a special target attached to a GPS receiver and panoramic images acquired in nadir view from different heights. The reference target is used as ground control to determine the exterior orientation parameters (EOPs) of the vertical images. These acquired multi-scale images overlap in the central region and can be used to compute ground coordinates using photogrammetric intersection. Experiments were conducted in a terrestrial calibration field to assess the geometry provided by the reference target and the quality of the reconstructed object coordinates. The analysis was based on the checkpoints, and the resulting discrepancies in the object space were less than 2 cm in the studied cases. As a result, small models and ortho-images can be produced as well as georeferenced image chips that can be used as high-quality control information

DETERMINATION of THE INDIRECT ORIENTATION of ORBITAL PUSHBROOM IMAGES USING CONTROL STRAIGHT LINES

The aim of this paper is to present an experimental assessment of two models that use "control lines'' for the indirect orientation of pushbroom imagery. Since pushbroom image acquisition is not instantaneous, six exterior orientation parameters (EOPs) must be estimated for each scanned line. The sensor position and attitude parameters are modelled with a time-dependent polynomial. The relationship between a straight line in the image space and its homologous form in the object space is established in the first model, based on the principle that the position vector containing an image point (projection ray) and the vector normal to the projection plane in the object space are orthogonal. The second model is based on the equivalence between the vector normal to the projection plane in the image space and the vector normal to the rotated projection plane in the object space. The equivalence property between planes was adapted to consider the pushbroom geometry. A model based on collinearity equations using points adapted to the pushbroom geometry was also implemented, aiming at a comparison of the methodologies. Six experiments using different sets of observations for indirect estimation of EOPs of images from the China-Brazil Earth Resources Satellite (CBERS) were carried out, by varying the geometric distribution and the number of straight lines. Also, experiments combining points and straight lines were accomplished. The results showed that an accuracy of around twice the ground sample distance (GSD) in the check points can be achieved with the models studied, which can then be used to estimate the EOPs of pushbroom images. Several other factors affecting the accuracy, such as the distribution and number of control features, were also assessed.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Bundle Block Adjustment of CBERS-2B HRC Imagery Combining Control Points and Lines

The aim of this work is to present the results of the assessment of rigorous bundle block adjustment models for orbital imagery of the High-Resolution Camera (HRC) of the CBERS (China-Brazil Earth Resources Satellite). The work is focused on the experimental assessment of the combined use of ground control points (GCP) and ground control lines (GCL) in a block adjustment. The mathematical models relating object and image spaces are based on collinearity (for points) and coplanarity (for lines) conditions with polynomial modelling of the spacecraft trajectory and attitude. These models were implemented in the software TMS (triangulation with multiple sensors) with multi-feature control (GCPs and GCLs) developed in-house. Experiments on a block of four CBERS-2B HRC images were accomplished using both GCPs and GCLs. The results show that the combination of the collinearity and coplanarity models can provide better results in the bundle block adjustment process than conventional bundle adjustment with GCPs only. A systematic error in the inner geometry of HRC camera caused by the displacement of one of the three CCD sensors and the lack of proper correction when fusing the three images to generate level 1 images was also verified. Experiments to evaluate the effects of this systematic error are also presented.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Experimental assessment of an automatic approach for stereo models generation using directly measured orientation parameters

With the evolution of digital image acquisition devices, satellite positioning systems (GPS) and space orientation by the inertial navigation systems (INS), new applications of fast cartography, became feasible, as disaster management and environment monitoring. Such applications require periodic georeferenced information with characteristics of speed and reliability that can be obtained by digital photogrammetry, using additional data from sensors of direct orientation. However, the exterior orientation parameters (EO) provided by these sensors are under the required accuracy to remove the vertical parallax in the model. This paper presents an experimental evaluation of an approach for removing the vertical parallax of the model. This appoach is based on the reprocessing of the EO parameters provided by the sensors, using a modified coplanarity model. Some experiments with simulated and real data are presented. The experiments with simulated data were performed in order to assess the acceptable errors in the exterior orientation parameters. The experiments with real data were carried out to evaluate the vertical parallax effect, before and after the reprocessing of the EO parameters, and to access the accuracy of check points calculated by photogrammetric intersection

A low-cost 3D reconstruction system using a single-shot projection of a pattern matrix

The purpose of this work is to present the main features of a structured light system and some experimental results. The system, named SingleShot3DSL, is based on a single off-the-shelf digital camera and a pattern projector. The mathematical model for 3D reconstruction is based on the collinearity equations. A pattern codification strategy was developed to allow fully automatic pattern recognition. A calibration methodology enables the determination of the direction vector of each pattern and the coordinates of the perspective centre of the pattern projector. The calibration processes are carried out with the acquisition of several images of a plane taken from different distances and orientations. Several processes were combined to provide a reliable solution for pattern location. In order to assess the accuracy and potential of the methodology a prototype was built, integrating a pattern projector and a digital camera in a single mount. Experiments using reconstructed surfaces with real data indicated that a relative accuracy of 0 center dot 2 mm in depth could be achieved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Vertical Optical Scanning with Panoramic Vision for Tree Trunk Reconstruction

This paper presents a practical application of a technique that uses a vertical optical flow with a fisheye camera to generate dense point clouds from a single planimetric station. Accurate data can be extracted to enable the measurement of tree trunks or branches. The images that are collected with this technique can be oriented in photogrammetric software (using fisheye models) and used to generate dense point clouds, provided that some constraints on the camera positions are adopted. A set of images was captured in a forest plot in the experiments. Weighted geometric constraints were imposed in the photogrammetric software to calculate the image orientation, perform dense image matching, and accurately generate a 3D point cloud. The tree trunks in the scenes were reconstructed and mapped in a local reference system. The accuracy assessment was based on differences between measured and estimated trunk diameters at different heights. Trunk sections from an image-based point cloud were also compared to the corresponding sections that were extracted from a dense terrestrial laser scanning (TLS) point cloud. Cylindrical fitting of the trunk sections allowed the assessment of the accuracies of the trunk geometric shapes in both clouds. The average difference between the cylinders that were fitted to the photogrammetric cloud and those to the TLS cloud was less than 1 cm, which indicates the potential of the proposed technique. The point densities that were obtained with vertical optical scanning were 1/3 less than those that were obtained with TLS. However, the point density can be improved by using higher resolution cameras