treatments were detected in uniformity of liquid distribution and capability to reach the inner p... more treatments were detected in uniformity of liquid distribution and capability to reach the inner parts of the crop. This important reduction in spray volume could be followed by an equivalent reduction of plant protection products but further research work is needed to guarantee biological efficacy of a reduced dose.
This paper describes an instrumental system developed to obtain geometric and structural paramete... more This paper describes an instrumental system developed to obtain geometric and structural parameters (phenotyping) of an olive orchard and the subsequent data process for the elaboration of raster maps of the parameters of interest. The system consists of a mobile terrestrial laser scanner (MTLS) based on a 2D LiDAR sensor and a RTK GPS, together with a data acquisition system consisting of a laptop computer. The olive orchard under study was an intensive plot of Olea Europaea cv. ‘Arbequina’ in Torres de Segre (Catalonia, Spain). The studied area was 1 ha and consisted of 16 rows that were scanned from both sides. The wide angular scan window of 270o allowed to simultaneously scan both sides of the olive tree rows while moving along each alley-way. Specific software has been developed to assign the corresponding UTM ETRS89 coordinates to each impact point and to extract various geometric parameters of interest for the agronomic management of olive orchards such as canopy height, wid...
The present work investigated the application of detailed airborne images and a resistivity soil ... more The present work investigated the application of detailed airborne images and a resistivity soil sensor (Veris 3100) to detect soil and crop spatial variability to assist in orchard management. The research was carried out in a peach orchard (Prunus persica). Soil apparent electrical conductivity (ECa), NDVI from a multispectral image (0.25 m/pixel) and soil properties at 40 sampling points (0–30 cm) were acquired. The ECa was standardized at 25°C. It showed a strong relationship with former landforms, altered by land levelling. A positive correlation of EC25 with EC1:5, water holding capacity at −1500 kPa and soil depth was found. NDVI was correlated only in the textural fractions coarser than clay. Two types of management zones were proposed: a) to improve the water holding capacity of soils and b) to regulate tree vigour and yield.
LiDAR (Light detection and ranging) technology is an alternative to current manual methods of can... more LiDAR (Light detection and ranging) technology is an alternative to current manual methods of canopy geometry estimations in orange trees. The objective of this work was to compare different types of canopy volume estimations of orange trees, some inspired on manual methods and others based on a LiDAR sensor. A point cloud was generated for 25 individual trees using a laser scanning system. The convex-hull and the alpha-shape surface reconstruction algorithms were tested. LiDAR derived models are able to represent orange trees more accurately than traditional methods. However, results differ significantly from the current manual method. In addition, different 3D modeling algorithms resulted in different canopy volume estimations. Therefore, a new standard method should be developed and established.
Different sampling schemes were tested to estimate yield (kg/tree), fruit firmness (kg) and the r... more Different sampling schemes were tested to estimate yield (kg/tree), fruit firmness (kg) and the refractometric index (°Baumé) in a peach orchard. In contrast to simple random sampling (SRS), the use of auxiliary information (NDVI and apparent electrical conductivity, ECa) allowed sampling points to be stratified according to two or three classes (strata) within the plot. Sampling schemes were compared in terms of accuracy and efficiency. Stratification of samples improved efficiency compared to SRS. However, yield and quality parameters may require different sampling strategies. While yield was better estimated using stratified samples based on the ECa, fruit quality (firmness and °Baumé) showed better results when stratifying by NDVI.
This work assesses the potential of Sentinel-2A images in precision agriculture for Barley produc... more This work assesses the potential of Sentinel-2A images in precision agriculture for Barley production in a case study. Two workflows are proposed: 1) images were acquired with a relatively simple methodology to follow the crop development; 2) two images around harvest time were downloaded and processed using a more complex and accurate methodology to calculate four vegetation indices (NDVI, WDRVI, GRVI and GNDVI) to be correlated to yield with linear regression models. Yield data were acquired with a yield monitor installed in a combine harvester. Green-based vegetation indices performed slightly better. However, the highest correlation coefficient was 0.48. Better results may be achieved with earlier imagery and other vegetation indices. Sentinel-2 is a promising tool for precision agriculture in large arable crop fields.
This study evaluated the capabilities of a LiDAR-based system to characterize poplar trees for bi... more This study evaluated the capabilities of a LiDAR-based system to characterize poplar trees for biomass production. The precision of the system was assessed by analyzing the relationship between the distance records and biophysical parameters. The terrestrial laser scanner (TLS) system consisted of a 2D time-of-flight LiDAR sensor, a gimbal to dynamically stabilize the sensor and a RTK-GPS to georeference its location and, subsequently, the sensor data. The sensor and its stabilizer were fixed facing downwards, on a metal frame designed for this purpose. Then, it was mounted on an all-terrain vehicle to perform 2D scans in planes perpendicular to the travel direction. Distances between the sensor and the surrounding objects had a high spatial resolution, providing high density 3D point clouds. Results on the reliability of the LiDAR system to estimate plant height showed a significant relationship between the sensor readings and actual poplar height and biomass data. In addition, tree biomass and tree volume were properly estimated in the point cloud. Regression analysis showed significant estimates of 0.79 and 0.89 for biomass and volume, respectively. These results reveal the potential of the LiDAR sensor to estimate both, plant height and plant biomass. This sensor's capability, added to its relative low cost, fast reaction, and the high number of readings per second consolidate the ideal system for estimating the productivity of biomass in energy crops.
The multi-angle plant reconstruction obtained from sensors such as Microsoft Kinect creates reali... more The multi-angle plant reconstruction obtained from sensors such as Microsoft Kinect creates realistic models. However, a full 3D reconstruction from every angle is not possible at present under field conditions. When an on-the-go measurement is taken, the sensor must be fixed to a vehicle and its best position needs to be determined. The objective of this study was to assess the possibilities of the Microsoft Kinect for Windows v1 sensor to quantify the biomass of poplar trees using different angles from a stationary position, in other words, to explore the best location of the sensor with respect to the trees. For this purpose, readings were obtained by placing the sensor at one meter from the tree, comparing four different view angles: top view (0°), 45°, perpendicular (90°) and ground (-45°). Good correlations between dry biomass and calculated plant surface area from measured raw data were found. The comparison of the different view angles revealed that top view showed poorer results due to top leaves occluding lower leaves. However, the other views led to good results. Consequently, the Microsoft Kinect for Windows v1 sensor can provide reliable information about crop biomass.
This paper describes an instrumental system developed to obtain geometric and structural paramete... more This paper describes an instrumental system developed to obtain geometric and structural parameters (phenotyping) of an olive orchard and the subsequent data process for the elaboration of raster maps of the parameters of interest. The system consists of a mobile terrestrial laser scanner (MTLS) based on a 2D LiDAR sensor and a RTK GPS, together with a data acquisition system consisting of a laptop computer. The olive orchard under study was an intensive plot of Olea Europaea cv. 'Arbequina' in Torres de Segre (Catalonia, Spain). The studied area was 1 ha and consisted of 16 rows that were scanned from both sides. The wide angular scan window of 270º allowed to simultaneously scan both sides of the olive tree rows while moving along each alley-way. Specific software has been developed to assign the corresponding UTM ETRS89 coordinates to each impact point and to extract various geometric parameters of interest for the agronomic management of olive orchards such as canopy height, width and volume. Additionally, data to build the digital terrain model (DTM) for the study area were also obtained. The maps built showed a clear spatial variability and confirmed the usefulness of MTLS for the measurement and mapping of relevant vegetative characteristics. This information can be used in the decision making process to decide whether a site-specific management under the framework of precision agriculture could be convenient. This research may be also useful to characterize other agricultural tree crops. Further research should be conducted in order to obtain information on canopy porosity, leaf area and leaf distribution and density taking.
The optimization of most pesticide and fertilizer applications is based on overall grove conditio... more The optimization of most pesticide and fertilizer applications is based on overall grove conditions. In this work we propose a measurement system based on a ground laser scanner to estimate the volume of the trees and then extrapolate their foliage surface in real-time. Tests with pear trees demonstrated that the relation between the volume and the foliage can be interpreted as linear with a coefficient of correlation (R) of 0.81 and the foliar surface can be estimated with an average error less than 5 %.
A new approach is described for automatic discrimination of grasses and broad-leaved weeds, based... more A new approach is described for automatic discrimination of grasses and broad-leaved weeds, based on their heights. An ultrasonic sensor was mounted on the front of a tractor, pointing straight downwards to the ground in the inter-row area, with a control system georeferencing and registering the echoes reflected by the ground or by the various leaf layers. Static measurements were conducted at locations with different densities of grasses (Sorghum halepense) and broad-leaved weeds (Xanthium strumarium and Datura spp.). The sensor readings permitted the discrimination of pure stands of grasses (up to 81% success) and pure stands of broad-leaved weeds (up to 99% success). Moreover, canonical discriminant analysis revealed that the ultrasonic data could separate three groups of assemblages: pure stands of broad-leaved (lower height), pure stands of grasses (higher height) or mixed stands of broadleaved and grasses (medium height). Dynamic measurements confirmed the potential of this system to detect weed infestations. This technique offers significant promise in the development of real-time spatially selective weed control techniques, either as the sole weed detection system or in combination with other detection tools.
Spraying techniques have been undergoing continuous evolution in recent decades. This paper prese... more Spraying techniques have been undergoing continuous evolution in recent decades. This paper presents part of the research work carried out in Spain in the field of sensors for characterizing vineyard canopies and monitoring spray drift in order to improve vineyard spraying and make it more sustainable. Some methods and geostatistical procedures for mapping vineyard parameters are proposed, and the development of a variable rate sprayer is described. All these technologies are interesting in terms of adjusting the amount of pesticides applied to the target canopy.
Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and ... more Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The
Canopy characterization is a key factor to improve pesticide application methods in tree crops an... more Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the use of ultrasonic and LIDAR sensors have been compared with the traditional manual and destructive canopy measurement procedure. For both methods the values of key parameters such as crop height, crop width, crop volume or leaf area have been compared. Obtained results indicate that an ultrasonic sensor is an appropriate tool to determine the average canopy characteristics, while a LIDAR sensor provides more accuracy and detailed information about the canopy. Good correlations have been obtained between crop volume (C VU) values measured with ultrasonic sensors and leaf area index, LAI (R 2 = 0.51). A good correlation has also been obtained between the canopy volume measured with ultrasonic and LIDAR sensors (R 2 = 0.52). Laser measurements of crop height (C HL) allow one to accurately predict the canopy volume. The proposed new technologies seems very appropriate as complementary tools to improve the efficiency of pesticide applications, although further improvements are still needed.
treatments were detected in uniformity of liquid distribution and capability to reach the inner p... more treatments were detected in uniformity of liquid distribution and capability to reach the inner parts of the crop. This important reduction in spray volume could be followed by an equivalent reduction of plant protection products but further research work is needed to guarantee biological efficacy of a reduced dose.
This paper describes an instrumental system developed to obtain geometric and structural paramete... more This paper describes an instrumental system developed to obtain geometric and structural parameters (phenotyping) of an olive orchard and the subsequent data process for the elaboration of raster maps of the parameters of interest. The system consists of a mobile terrestrial laser scanner (MTLS) based on a 2D LiDAR sensor and a RTK GPS, together with a data acquisition system consisting of a laptop computer. The olive orchard under study was an intensive plot of Olea Europaea cv. ‘Arbequina’ in Torres de Segre (Catalonia, Spain). The studied area was 1 ha and consisted of 16 rows that were scanned from both sides. The wide angular scan window of 270o allowed to simultaneously scan both sides of the olive tree rows while moving along each alley-way. Specific software has been developed to assign the corresponding UTM ETRS89 coordinates to each impact point and to extract various geometric parameters of interest for the agronomic management of olive orchards such as canopy height, wid...
The present work investigated the application of detailed airborne images and a resistivity soil ... more The present work investigated the application of detailed airborne images and a resistivity soil sensor (Veris 3100) to detect soil and crop spatial variability to assist in orchard management. The research was carried out in a peach orchard (Prunus persica). Soil apparent electrical conductivity (ECa), NDVI from a multispectral image (0.25 m/pixel) and soil properties at 40 sampling points (0–30 cm) were acquired. The ECa was standardized at 25°C. It showed a strong relationship with former landforms, altered by land levelling. A positive correlation of EC25 with EC1:5, water holding capacity at −1500 kPa and soil depth was found. NDVI was correlated only in the textural fractions coarser than clay. Two types of management zones were proposed: a) to improve the water holding capacity of soils and b) to regulate tree vigour and yield.
LiDAR (Light detection and ranging) technology is an alternative to current manual methods of can... more LiDAR (Light detection and ranging) technology is an alternative to current manual methods of canopy geometry estimations in orange trees. The objective of this work was to compare different types of canopy volume estimations of orange trees, some inspired on manual methods and others based on a LiDAR sensor. A point cloud was generated for 25 individual trees using a laser scanning system. The convex-hull and the alpha-shape surface reconstruction algorithms were tested. LiDAR derived models are able to represent orange trees more accurately than traditional methods. However, results differ significantly from the current manual method. In addition, different 3D modeling algorithms resulted in different canopy volume estimations. Therefore, a new standard method should be developed and established.
Different sampling schemes were tested to estimate yield (kg/tree), fruit firmness (kg) and the r... more Different sampling schemes were tested to estimate yield (kg/tree), fruit firmness (kg) and the refractometric index (°Baumé) in a peach orchard. In contrast to simple random sampling (SRS), the use of auxiliary information (NDVI and apparent electrical conductivity, ECa) allowed sampling points to be stratified according to two or three classes (strata) within the plot. Sampling schemes were compared in terms of accuracy and efficiency. Stratification of samples improved efficiency compared to SRS. However, yield and quality parameters may require different sampling strategies. While yield was better estimated using stratified samples based on the ECa, fruit quality (firmness and °Baumé) showed better results when stratifying by NDVI.
This work assesses the potential of Sentinel-2A images in precision agriculture for Barley produc... more This work assesses the potential of Sentinel-2A images in precision agriculture for Barley production in a case study. Two workflows are proposed: 1) images were acquired with a relatively simple methodology to follow the crop development; 2) two images around harvest time were downloaded and processed using a more complex and accurate methodology to calculate four vegetation indices (NDVI, WDRVI, GRVI and GNDVI) to be correlated to yield with linear regression models. Yield data were acquired with a yield monitor installed in a combine harvester. Green-based vegetation indices performed slightly better. However, the highest correlation coefficient was 0.48. Better results may be achieved with earlier imagery and other vegetation indices. Sentinel-2 is a promising tool for precision agriculture in large arable crop fields.
This study evaluated the capabilities of a LiDAR-based system to characterize poplar trees for bi... more This study evaluated the capabilities of a LiDAR-based system to characterize poplar trees for biomass production. The precision of the system was assessed by analyzing the relationship between the distance records and biophysical parameters. The terrestrial laser scanner (TLS) system consisted of a 2D time-of-flight LiDAR sensor, a gimbal to dynamically stabilize the sensor and a RTK-GPS to georeference its location and, subsequently, the sensor data. The sensor and its stabilizer were fixed facing downwards, on a metal frame designed for this purpose. Then, it was mounted on an all-terrain vehicle to perform 2D scans in planes perpendicular to the travel direction. Distances between the sensor and the surrounding objects had a high spatial resolution, providing high density 3D point clouds. Results on the reliability of the LiDAR system to estimate plant height showed a significant relationship between the sensor readings and actual poplar height and biomass data. In addition, tree biomass and tree volume were properly estimated in the point cloud. Regression analysis showed significant estimates of 0.79 and 0.89 for biomass and volume, respectively. These results reveal the potential of the LiDAR sensor to estimate both, plant height and plant biomass. This sensor's capability, added to its relative low cost, fast reaction, and the high number of readings per second consolidate the ideal system for estimating the productivity of biomass in energy crops.
The multi-angle plant reconstruction obtained from sensors such as Microsoft Kinect creates reali... more The multi-angle plant reconstruction obtained from sensors such as Microsoft Kinect creates realistic models. However, a full 3D reconstruction from every angle is not possible at present under field conditions. When an on-the-go measurement is taken, the sensor must be fixed to a vehicle and its best position needs to be determined. The objective of this study was to assess the possibilities of the Microsoft Kinect for Windows v1 sensor to quantify the biomass of poplar trees using different angles from a stationary position, in other words, to explore the best location of the sensor with respect to the trees. For this purpose, readings were obtained by placing the sensor at one meter from the tree, comparing four different view angles: top view (0°), 45°, perpendicular (90°) and ground (-45°). Good correlations between dry biomass and calculated plant surface area from measured raw data were found. The comparison of the different view angles revealed that top view showed poorer results due to top leaves occluding lower leaves. However, the other views led to good results. Consequently, the Microsoft Kinect for Windows v1 sensor can provide reliable information about crop biomass.
This paper describes an instrumental system developed to obtain geometric and structural paramete... more This paper describes an instrumental system developed to obtain geometric and structural parameters (phenotyping) of an olive orchard and the subsequent data process for the elaboration of raster maps of the parameters of interest. The system consists of a mobile terrestrial laser scanner (MTLS) based on a 2D LiDAR sensor and a RTK GPS, together with a data acquisition system consisting of a laptop computer. The olive orchard under study was an intensive plot of Olea Europaea cv. 'Arbequina' in Torres de Segre (Catalonia, Spain). The studied area was 1 ha and consisted of 16 rows that were scanned from both sides. The wide angular scan window of 270º allowed to simultaneously scan both sides of the olive tree rows while moving along each alley-way. Specific software has been developed to assign the corresponding UTM ETRS89 coordinates to each impact point and to extract various geometric parameters of interest for the agronomic management of olive orchards such as canopy height, width and volume. Additionally, data to build the digital terrain model (DTM) for the study area were also obtained. The maps built showed a clear spatial variability and confirmed the usefulness of MTLS for the measurement and mapping of relevant vegetative characteristics. This information can be used in the decision making process to decide whether a site-specific management under the framework of precision agriculture could be convenient. This research may be also useful to characterize other agricultural tree crops. Further research should be conducted in order to obtain information on canopy porosity, leaf area and leaf distribution and density taking.
The optimization of most pesticide and fertilizer applications is based on overall grove conditio... more The optimization of most pesticide and fertilizer applications is based on overall grove conditions. In this work we propose a measurement system based on a ground laser scanner to estimate the volume of the trees and then extrapolate their foliage surface in real-time. Tests with pear trees demonstrated that the relation between the volume and the foliage can be interpreted as linear with a coefficient of correlation (R) of 0.81 and the foliar surface can be estimated with an average error less than 5 %.
A new approach is described for automatic discrimination of grasses and broad-leaved weeds, based... more A new approach is described for automatic discrimination of grasses and broad-leaved weeds, based on their heights. An ultrasonic sensor was mounted on the front of a tractor, pointing straight downwards to the ground in the inter-row area, with a control system georeferencing and registering the echoes reflected by the ground or by the various leaf layers. Static measurements were conducted at locations with different densities of grasses (Sorghum halepense) and broad-leaved weeds (Xanthium strumarium and Datura spp.). The sensor readings permitted the discrimination of pure stands of grasses (up to 81% success) and pure stands of broad-leaved weeds (up to 99% success). Moreover, canonical discriminant analysis revealed that the ultrasonic data could separate three groups of assemblages: pure stands of broad-leaved (lower height), pure stands of grasses (higher height) or mixed stands of broadleaved and grasses (medium height). Dynamic measurements confirmed the potential of this system to detect weed infestations. This technique offers significant promise in the development of real-time spatially selective weed control techniques, either as the sole weed detection system or in combination with other detection tools.
Spraying techniques have been undergoing continuous evolution in recent decades. This paper prese... more Spraying techniques have been undergoing continuous evolution in recent decades. This paper presents part of the research work carried out in Spain in the field of sensors for characterizing vineyard canopies and monitoring spray drift in order to improve vineyard spraying and make it more sustainable. Some methods and geostatistical procedures for mapping vineyard parameters are proposed, and the development of a variable rate sprayer is described. All these technologies are interesting in terms of adjusting the amount of pesticides applied to the target canopy.
Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and ... more Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The
Canopy characterization is a key factor to improve pesticide application methods in tree crops an... more Canopy characterization is a key factor to improve pesticide application methods in tree crops and vineyards. Development of quick, easy and efficient methods to determine the fundamental parameters used to characterize canopy structure is thus an important need. In this research the use of ultrasonic and LIDAR sensors have been compared with the traditional manual and destructive canopy measurement procedure. For both methods the values of key parameters such as crop height, crop width, crop volume or leaf area have been compared. Obtained results indicate that an ultrasonic sensor is an appropriate tool to determine the average canopy characteristics, while a LIDAR sensor provides more accuracy and detailed information about the canopy. Good correlations have been obtained between crop volume (C VU) values measured with ultrasonic sensors and leaf area index, LAI (R 2 = 0.51). A good correlation has also been obtained between the canopy volume measured with ultrasonic and LIDAR sensors (R 2 = 0.52). Laser measurements of crop height (C HL) allow one to accurately predict the canopy volume. The proposed new technologies seems very appropriate as complementary tools to improve the efficiency of pesticide applications, although further improvements are still needed.
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