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Prof. Fernando Carvajal-Ramírez
University of Almeria (Spain)

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0 Agricultural Engineering
0 Heritage Buildings
0 Remote Sensing
0 Low altitude remote sensing technology
0 Environemntal Application

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UAV photogrammetry
Remote Sensing
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Editorial
Published: 13 June 2021 in Remote Sensing
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The concept of Remote Sensing as a way of capturing information from an object without making contact with it has, until recently, been exclusively focused on the use of earth observation satellites

ACS Style

Fernando Carvajal-Ramírez; Francisco Agüera-Vega; Patricio Martínez-Carricondo. Editorial for Special Issue “UAV Photogrammetry and Remote Sensing”. Remote Sensing 2021, 13, 2327 .

AMA Style

Fernando Carvajal-Ramírez, Francisco Agüera-Vega, Patricio Martínez-Carricondo. Editorial for Special Issue “UAV Photogrammetry and Remote Sensing”. Remote Sensing. 2021; 13 (12):2327.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; Francisco Agüera-Vega; Patricio Martínez-Carricondo. 2021. "Editorial for Special Issue “UAV Photogrammetry and Remote Sensing”." Remote Sensing 13, no. 12: 2327.

Journal article
Published: 30 July 2020 in Remote Sensing
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Unmanned aerial vehicle (UAV) photogrammetry has recently emerged as a popular solution to obtain certain products necessary in linear projects, such as orthoimages or digital surface models. This is mainly due to its ability to provide these topographic products in a fast and economical way. In order to guarantee a certain degree of accuracy, it is important to know how many ground control points (GCPs) are necessary and how to distribute them across the study site. The purpose of this work consists of determining the number of GCPs and how to distribute them in a way that yields higher accuracy for a corridor-shaped study area. To do so, several photogrammetric projects have been carried out in which the number of GCPs used in the bundle adjustment and their distribution vary. The different projects were assessed taking into account two different parameters: the root mean square error (RMSE) and the Multiscale Model to Model Cloud Comparison (M3C2). From the different configurations tested, the projects using 9 and 11 GCPs (4.3 and 5.2 GCPs km−1, respectively) distributed alternatively on both sides of the road in an offset or zigzagging pattern, with a pair of GCPs at each end of the road, yielded optimal results regarding fieldwork cost, compared to projects using similar or more GCPs placed according to other distributions.

ACS Style

Ezequiel Ferrer-González; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Martínez-Carricondo. UAV Photogrammetry Accuracy Assessment for Corridor Mapping Based on the Number and Distribution of Ground Control Points. Remote Sensing 2020, 12, 2447 .

AMA Style

Ezequiel Ferrer-González, Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Patricio Martínez-Carricondo. UAV Photogrammetry Accuracy Assessment for Corridor Mapping Based on the Number and Distribution of Ground Control Points. Remote Sensing. 2020; 12 (15):2447.

Chicago/Turabian Style

Ezequiel Ferrer-González; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Martínez-Carricondo. 2020. "UAV Photogrammetry Accuracy Assessment for Corridor Mapping Based on the Number and Distribution of Ground Control Points." Remote Sensing 12, no. 15: 2447.

Journal article
Published: 10 July 2020 in Remote Sensing
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In this study, an analysis of the capabilities of unmanned aerial vehicle (UAV) photogrammetry to obtain point clouds from areas with a near-vertical inclination was carried out. For this purpose, 18 different combinations were proposed, varying the number of ground control points (GCPs), the adequacy (or not) of the distribution of GCPs, and the orientation of the photographs (nadir and oblique). The results have shown that under certain conditions, the accuracy achieved was similar to those obtained by a terrestrial laser scanner (TLS). For this reason, it is necessary to increase the number of GCPs as much as possible in order to cover a whole study area. In the event that this is not possible, the inclusion of oblique photography ostensibly improves results; therefore, it is always advisable since they also improve the geometric descriptions of break lines or sudden changes in slope. In this sense, UAVs seem to be a more economic substitute compared to TLS for vertical wall surveying.

ACS Style

Patricio Martínez-Carricondo; Francisco Agüera-Vega; Fernando Carvajal-Ramírez. Use of UAV-Photogrammetry for Quasi-Vertical Wall Surveying. Remote Sensing 2020, 12, 2221 .

AMA Style

Patricio Martínez-Carricondo, Francisco Agüera-Vega, Fernando Carvajal-Ramírez. Use of UAV-Photogrammetry for Quasi-Vertical Wall Surveying. Remote Sensing. 2020; 12 (14):2221.

Chicago/Turabian Style

Patricio Martínez-Carricondo; Francisco Agüera-Vega; Fernando Carvajal-Ramírez. 2020. "Use of UAV-Photogrammetry for Quasi-Vertical Wall Surveying." Remote Sensing 12, no. 14: 2221.

Drones paper
Published: 18 June 2020 in International Journal of Remote Sensing
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The objective of this study was to evaluate the effects of the three dimensional (3D) point cloud density derived from Unmanned Aerial Vehicle (UAV) photogrammetry (using Structure from Motion (SfM) and Multi-View Stereopsis (MVS) techniques), the interpolation method for generating a digital terrain model (DTM), and the resolution (grid size (GS)) of the derived DTM on the accuracy of estimated heights in small areas, where a very accurate high spatial resolution is required. A UAV-photogrammetry project was carried out on 13 m × 13 m bare soil with a rotatory wing UAV at 10 m flight altitude (equivalent ground sample distance = 0.4 cm), and the 3D point cloud was derived. A stratified random sample (200 points in each square metre) was extracted and from the rest of the cloud, 15 stratified random samples representing 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, and 90% were extracted. Five replications of each percentage were extracted to analyse the effect of cloud density on DTM accuracy. For each of these 15 × 5 = 75 samples, DTMs were derived using four different interpolation methods (Inverse Distance Weighted (IDW), Multiquadric Radial Basis Function (MRBF), Kriging (KR), and Triangulation with Linear Interpolation (TLI)) and 15 DTM GS values (20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.67, 0.50, and 0.40 cm). Then, 75 × 4 × 15 = 4500 DTMs were analysed. The results showed an optimal GS value for each interpolation method and each density (most of the cases were equal to 1 cm) for which the Root Mean Square Error (RMSE) was the minimum. IDW was the interpolator that yielded the best accuracies for all combinations of densities and GS. Its RMSE when considering the raw cloud was 1.054 cm and increased by 3% when a point cloud with 80% extracted from the raw cloud was used to generate the DTM. When the point cloud included 40% of the raw cloud, RMSE increased by 5%. For densities lower than 15%, RMSE increased exponentially (45% for 1% of raw cloud). The GS minimizing RMSE for densities of 20% or higher was 1 cm, which represents 2.5 times the ground sample distance of the pictures used for developing the photogrammetry project.

ACS Style

F. Agüera-Vega; M. Agüera-Puntas; P. Martínez-Carricondo; F. Mancini; F. Carvajal. Effects of point cloud density, interpolation method and grid size on derived Digital Terrain Model accuracy at micro topography level. International Journal of Remote Sensing 2020, 41, 8281 -8299.

AMA Style

F. Agüera-Vega, M. Agüera-Puntas, P. Martínez-Carricondo, F. Mancini, F. Carvajal. Effects of point cloud density, interpolation method and grid size on derived Digital Terrain Model accuracy at micro topography level. International Journal of Remote Sensing. 2020; 41 (21):8281-8299.

Chicago/Turabian Style

F. Agüera-Vega; M. Agüera-Puntas; P. Martínez-Carricondo; F. Mancini; F. Carvajal. 2020. "Effects of point cloud density, interpolation method and grid size on derived Digital Terrain Model accuracy at micro topography level." International Journal of Remote Sensing 41, no. 21: 8281-8299.

Journal article
Published: 06 May 2020 in Sustainability
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The Montado ecosystem, predominant in the Mediterranean region, consists of poor soils, a sparse cover of cork and holm with an understory of natural biodiverse pastures, grazed by animals in extensive regime. The recommended procedure for increasing productivity of these pastures is based on the application of phosphate fertilizer. One of the main productivity-limiting factors is, however, associated with soil acidity. The objective of this work was to evaluate the simultaneous effect of the holm oak canopy and the application of dolomitic lime on the productivity and quality of a permanent biodiverse pasture, grazed by sheep, in an acid soil (pH = 5.4 ± 0.3). Pasture was monitored at the end of autumn 2018 and winter and spring 2019. The results show that amendment of soil acidity is a slow and gradual process that improves soil Mg/Mn ratio and has a positive impact on pasture productivity and quality. Pasture crude protein availability (CP, kg·ha−1), which is based on both pasture dry matter yield (kg·ha−1) and quality (CP, %), proved to be a very practical indicator of the contributions of tree canopy and soil acidity correction to the holistic management of the Montado ecosystem.

ACS Style

João Serrano; Shakib Shahidian; José Marques Da Silva; Francisco Moral; Fernando Carvajal-Ramirez; Emanuel Carreira; Alfredo Pereira; Mário De Carvalho. Evaluation of the Effect of Dolomitic Lime Application on Pastures—Case Study in the Montado Mediterranean Ecosystem. Sustainability 2020, 12, 3758 .

AMA Style

João Serrano, Shakib Shahidian, José Marques Da Silva, Francisco Moral, Fernando Carvajal-Ramirez, Emanuel Carreira, Alfredo Pereira, Mário De Carvalho. Evaluation of the Effect of Dolomitic Lime Application on Pastures—Case Study in the Montado Mediterranean Ecosystem. Sustainability. 2020; 12 (9):3758.

Chicago/Turabian Style

João Serrano; Shakib Shahidian; José Marques Da Silva; Francisco Moral; Fernando Carvajal-Ramirez; Emanuel Carreira; Alfredo Pereira; Mário De Carvalho. 2020. "Evaluation of the Effect of Dolomitic Lime Application on Pastures—Case Study in the Montado Mediterranean Ecosystem." Sustainability 12, no. 9: 3758.

Journal article
Published: 25 April 2020 in AgriEngineering
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The estimation of pasture productivity is of great interest for the management of animal grazing. The standard method of assessing pasture mass requires great effort and expense to collect enough samples to accurately represent a pasture. This work presents the results of a long-term study to calibrate a Grassmaster II capacitance probe to estimate pasture productivity in two phases: (i) the calibration phase (2007–2018), which included measurements in 1411 sampling points in three parcels; and (ii) the validation phase (2019), which included measurements in 216 sampling points in eight parcels. A regression analysis was performed between the capacitance (CMR) measured by the probe and values of pasture green matter and dry matter (respectively, GM and DM, in kg ha−1). The results showed significant correlations between GM and CMR and between DM and CMR, especially in the early stages of pasture growth cycle. The analysis of the data grouped by classes of pasture moisture content (PMC) shows higher correlation coefficients for PMC content >80% (r = 0.775; p < 0.01; RMSE = 4806 kg ha−1 and CVRMSE = 28.1% for GM; r = 0.750; p < 0.01; RMSE = 763 kg ha−1 and CVRMSE = 29.7% for DM), with a clear tendency for the accuracy to decrease when the pasture vegetative cycle advances and, consequently, the PMC decreases. The validation of calibration equations when PMC > 80% showed a good approximation between GM or DM measured and GM or DM predicted (r = 0.959; p < 0.01; RMSE = 3191 kg ha−1; CVRMSE = 23.6% for GM; r = 0.953; p 80%.

ACS Style

João Serrano; Shakib Shahidian; Francisco Moral; Fernando Carvajal-Ramirez; José Marques Da Silva. Estimation of Productivity in Dryland Mediterranean Pastures: Long-Term Field Tests to Calibration and Validation of the Grassmaster II Probe. AgriEngineering 2020, 2, 240 -255.

AMA Style

João Serrano, Shakib Shahidian, Francisco Moral, Fernando Carvajal-Ramirez, José Marques Da Silva. Estimation of Productivity in Dryland Mediterranean Pastures: Long-Term Field Tests to Calibration and Validation of the Grassmaster II Probe. AgriEngineering. 2020; 2 (2):240-255.

Chicago/Turabian Style

João Serrano; Shakib Shahidian; Francisco Moral; Fernando Carvajal-Ramirez; José Marques Da Silva. 2020. "Estimation of Productivity in Dryland Mediterranean Pastures: Long-Term Field Tests to Calibration and Validation of the Grassmaster II Probe." AgriEngineering 2, no. 2: 240-255.

Journal article
Published: 03 November 2019 in Remote Sensing
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Management and control operations are crucial for preventing forest fires, especially in Mediterranean forest areas with dry climatic periods. One of them is prescribed fires, in which the biomass fuel present in the controlled plot area must be accurately estimated. The most used methods for estimating biomass are time-consuming and demand too much manpower. Unmanned aerial vehicles (UAVs) carrying multispectral sensors can be used to carry out accurate indirect measurements of terrain and vegetation morphology and their radiometric characteristics. Based on the UAV-photogrammetric project products, four estimators of phytovolume were compared in a Mediterranean forest area, all obtained using the difference between a digital surface model (DSM) and a digital terrain model (DTM). The DSM was derived from a UAV-photogrammetric project based on the structure from a motion algorithm. Four different methods for obtaining a DTM were used based on an unclassified dense point cloud produced through a UAV-photogrammetric project (FFU), an unsupervised classified dense point cloud (FFC), a multispectral vegetation index (FMI), and a cloth simulation filter (FCS). Qualitative and quantitative comparisons determined the ability of the phytovolume estimators for vegetation detection and occupied volume. The results show that there are no significant differences in surface vegetation detection between all the pairwise possible comparisons of the four estimators at a 95% confidence level, but FMI presented the best kappa value (0.678) in an error matrix analysis with reference data obtained from photointerpretation and supervised classification. Concerning the accuracy of phytovolume estimation, only FFU and FFC presented differences higher than two standard deviations in a pairwise comparison, and FMI presented the best RMSE (12.3 m) when the estimators were compared to 768 observed data points grouped in four 500 m2 sample plots. The FMI was the best phytovolume estimator of the four compared for low vegetation height in a Mediterranean forest. The use of FMI based on UAV data provides accurate phytovolume estimations that can be applied on several environment management activities, including wildfire prevention. Multitemporal phytovolume estimations based on FMI could help to model the forest resources evolution in a very realistic way.

ACS Style

Fernando Carvajal-Ramírez; João Manuel Pereira Ramalho Serrano; Francisco Agüera-Vega; Patricio Martínez-Carricondo. A Comparative Analysis of Phytovolume Estimation Methods Based on UAV-Photogrammetry and Multispectral Imagery in a Mediterranean Forest. Remote Sensing 2019, 11, 2579 .

AMA Style

Fernando Carvajal-Ramírez, João Manuel Pereira Ramalho Serrano, Francisco Agüera-Vega, Patricio Martínez-Carricondo. A Comparative Analysis of Phytovolume Estimation Methods Based on UAV-Photogrammetry and Multispectral Imagery in a Mediterranean Forest. Remote Sensing. 2019; 11 (21):2579.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; João Manuel Pereira Ramalho Serrano; Francisco Agüera-Vega; Patricio Martínez-Carricondo. 2019. "A Comparative Analysis of Phytovolume Estimation Methods Based on UAV-Photogrammetry and Multispectral Imagery in a Mediterranean Forest." Remote Sensing 11, no. 21: 2579.

Articles
Published: 16 May 2019 in Building Research & Information
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Historic Building Information Modelling (HBIM) is the most effective method of rebuilding virtual 3D models of heritage buildings, and constitutes a new information management system in the field of cultural heritage interventions. In this study, photogrammetry based on Unmanned Aerial Vehicles (UAV photogrammetry) was applied as an alternative to Terrestrial Laser Scanning (TLS) for the development of HBIM for historical buildings in a ruinous state, analysing as a case study the Cortijo del Fraile, in Níjar, Almería (Spain). Based on the analysis of the historical information of the building, a photogrammetric survey was carried out with UAV by means of a combination of nadiral and oblique photographs. In this way, a precise characterization of the object was obtained, avoiding the grey areas that are characteristic of TLS. The generated 3D point cloud served as the basis for the virtual reconstruction of an HBIM model focused on both the exterior and interior. In order to ensure reasonable agreement between the parametric model and the ground truth, a validation procedure has been established that restricts the deviations between the two. Finally, a texturizing process is applied to the HBIM model to achieve a photorealistic finish for purposes of visualization, archiving, and recording.

ACS Style

Patricio Martínez-Carricondo; Fernando Carvajal-Ramírez; Lourdes Yero-Paneque; Francisco Agüera-Vega. Combination of nadiral and oblique UAV photogrammetry and HBIM for the virtual reconstruction of cultural heritage. Case study of Cortijo del Fraile in Níjar, Almería (Spain). Building Research & Information 2019, 48, 140 -159.

AMA Style

Patricio Martínez-Carricondo, Fernando Carvajal-Ramírez, Lourdes Yero-Paneque, Francisco Agüera-Vega. Combination of nadiral and oblique UAV photogrammetry and HBIM for the virtual reconstruction of cultural heritage. Case study of Cortijo del Fraile in Níjar, Almería (Spain). Building Research & Information. 2019; 48 (2):140-159.

Chicago/Turabian Style

Patricio Martínez-Carricondo; Fernando Carvajal-Ramírez; Lourdes Yero-Paneque; Francisco Agüera-Vega. 2019. "Combination of nadiral and oblique UAV photogrammetry and HBIM for the virtual reconstruction of cultural heritage. Case study of Cortijo del Fraile in Níjar, Almería (Spain)." Building Research & Information 48, no. 2: 140-159.

Journal article
Published: 26 April 2019 in Remote Sensing
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Fire severity is a key factor for management of post-fire vegetation regeneration strategies because it quantifies the impact of fire, describing the amount of damage. Several indices have been developed for estimation of fire severity based on terrestrial observation by satellite imagery. In order to avoid the implicit limitations of this kind of data, this work employed an Unmanned Aerial Vehicle (UAV) carrying a high-resolution multispectral sensor including green, red, near-infrared, and red edge bands. Flights were carried out pre- and post-controlled fire in a Mediterranean forest. The products obtained from the UAV-photogrammetric projects based on the Structure from Motion (SfM) algorithm were a Digital Surface Model (DSM) and multispectral images orthorectified in both periods and co-registered in the same absolute coordinate system to find the temporal differences (d) between pre- and post-fire values of the Excess Green Index (EGI), Normalized Difference Vegetation Index (NDVI), and Normalized Difference Red Edge (NDRE) index. The differences of indices (dEGI, dNDVI, and dNDRE) were reclassified into fire severity classes, which were compared with the reference data identified through the in situ fire damage location and Artificial Neural Network classification. Applying an error matrix analysis to the three difference of indices, the overall Kappa accuracies of the severity maps were 0.411, 0.563, and 0.211 and the Cramer’s Value statistics were 0.411, 0.582, and 0.269 for dEGI, dNDVI, and dNDRE, respectively. The chi-square test, used to compare the average of each severity class, determined that there were no significant differences between the three severity maps, with a 95% confidence level. It was concluded that dNDVI was the index that best estimated the fire severity according to the UAV flight conditions and sensor specifications.

ACS Style

Fernando Carvajal-Ramírez; José Rafael Marques Da Silva; Francisco Agüera-Vega; Patricio Martínez-Carricondo; João Serrano; Francisco Jesús Moral. Evaluation of Fire Severity Indices Based on Pre- and Post-Fire Multispectral Imagery Sensed from UAV. Remote Sensing 2019, 11, 993 .

AMA Style

Fernando Carvajal-Ramírez, José Rafael Marques Da Silva, Francisco Agüera-Vega, Patricio Martínez-Carricondo, João Serrano, Francisco Jesús Moral. Evaluation of Fire Severity Indices Based on Pre- and Post-Fire Multispectral Imagery Sensed from UAV. Remote Sensing. 2019; 11 (9):993.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; José Rafael Marques Da Silva; Francisco Agüera-Vega; Patricio Martínez-Carricondo; João Serrano; Francisco Jesús Moral. 2019. "Evaluation of Fire Severity Indices Based on Pre- and Post-Fire Multispectral Imagery Sensed from UAV." Remote Sensing 11, no. 9: 993.

Journal article
Published: 27 December 2018 in Measurement
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Knowledge about cultural and archaeological heritage can dissolve or even disappear with the passage of time, especially when the protection level of the archaeological site is weak. The recent development of techniques based on remote sensing from remotely controlled light platforms, so-called Unmanned Aerial Vehicles (UAV) or drones, carrying sensors in visible and other spectral ranges, allows to measure efficiently the current surface morphology of a damaged archaeological site. In this work, a deteriorated and unique archaeological site due its chronological and functional singularity was chosen as the study case. Mound structures made of stone, interconnected one to each other in a regular network, covered by vaults, and well adapted to a smooth slope topography have no known precedents in the Iberian Peninsula in the Bronze Age. Nowadays, this site is seriously damaged, and its protection level by the administrations is weak. Nevertheless, two archaeological campaigns were carried out recording interesting information. A UAV-Photogrammetry project based on Structure from Motion (SfM) and Multi-View Stereopsis (MVS) algorithms was applied to model the surface terrain where the structural basis and connection channels were built, obtaining a dense point cloud, an orthoimage and a Digital Surface Model (DSM). The topographic data covering altered areas were removed from the dense point cloud, and then a new interpolated surface was obtained representing the unaltered morphology. Finally, the information recorded in the archaeological campaigns was materialised in a virtual reconstruction located between both surfaces, measured by UAV-Photogrammetry and interpolated, and then the original architectural complex in its context was recreated and shared with the scientific community through Google Earth, contributing to recovering and preserving this cultural heritage, even after its disappearance.

ACS Style

Fernando Carvajal-Ramírez; Ana D. Navarro; Francisco Agüera-Vega; Patricio Jesús Martínez Carricondo; Francesco Mancini. Virtual reconstruction of damaged archaeological sites based on Unmanned Aerial Vehicle Photogrammetry and 3D modelling. Study case of a southeastern Iberia production area in the Bronze Age. Measurement 2018, 136, 225 -236.

AMA Style

Fernando Carvajal-Ramírez, Ana D. Navarro, Francisco Agüera-Vega, Patricio Jesús Martínez Carricondo, Francesco Mancini. Virtual reconstruction of damaged archaeological sites based on Unmanned Aerial Vehicle Photogrammetry and 3D modelling. Study case of a southeastern Iberia production area in the Bronze Age. Measurement. 2018; 136 ():225-236.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; Ana D. Navarro; Francisco Agüera-Vega; Patricio Jesús Martínez Carricondo; Francesco Mancini. 2018. "Virtual reconstruction of damaged archaeological sites based on Unmanned Aerial Vehicle Photogrammetry and 3D modelling. Study case of a southeastern Iberia production area in the Bronze Age." Measurement 136, no. : 225-236.

Journal article
Published: 01 October 2018 in International Journal of Applied Earth Observation and Geoinformation
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Civil engineering uses digital elevation models (DEMs) and orthophotos as basic material to be able to design and execute any project. UAV photogrammetry has made it possible to obtain this type of information in an economic and practical way. However, it is necessary to know the accuracy of the data and that it is within the admissible limits. There are many factors that affect the accuracy of products resulting from UAV photogrammetry. Of all of these, the effect of the number of ground control points (GCPs) and their distribution in the study area are especially significant. Different distributions of GCPs have been studied to try to optimize the products obtained by UAV photogrammetry. Of all the distributions tested, the best results were obtained with edge distribution and stratified distribution. Therefore, it is necessary to place GCPs around the edge of the study area to minimize planimetry errors. In addition, it is advisable to create a stratified distribution inside the study area with a density of around 0.5–1 GCP × ha−1 to minimize altimetry errors. The combination of these two distributions minimizes the total error obtained.

ACS Style

Patricio Jesús Martínez Carricondo; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Francisco-Javier Mesas-Carrascosa; Alfonso García-Ferrer; Fernando-Juan Pérez-Porras. Assessment of UAV-photogrammetric mapping accuracy based on variation of ground control points. International Journal of Applied Earth Observation and Geoinformation 2018, 72, 1 -10.

AMA Style

Patricio Jesús Martínez Carricondo, Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Francisco-Javier Mesas-Carrascosa, Alfonso García-Ferrer, Fernando-Juan Pérez-Porras. Assessment of UAV-photogrammetric mapping accuracy based on variation of ground control points. International Journal of Applied Earth Observation and Geoinformation. 2018; 72 ():1-10.

Chicago/Turabian Style

Patricio Jesús Martínez Carricondo; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Francisco-Javier Mesas-Carrascosa; Alfonso García-Ferrer; Fernando-Juan Pérez-Porras. 2018. "Assessment of UAV-photogrammetric mapping accuracy based on variation of ground control points." International Journal of Applied Earth Observation and Geoinformation 72, no. : 1-10.

Journal article
Published: 01 June 2018 in Measurement
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ACS Style

Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo; Julián Sánchez-Hermosilla López; Francisco Javier Mesas-Carrascosa; Alfonso García-Ferrer; Fernando Juan Pérez-Porras. Reconstruction of extreme topography from UAV structure from motion photogrammetry. Measurement 2018, 121, 127 -138.

AMA Style

Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Patricio Jesús Martínez Carricondo, Julián Sánchez-Hermosilla López, Francisco Javier Mesas-Carrascosa, Alfonso García-Ferrer, Fernando Juan Pérez-Porras. Reconstruction of extreme topography from UAV structure from motion photogrammetry. Measurement. 2018; 121 ():127-138.

Chicago/Turabian Style

Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo; Julián Sánchez-Hermosilla López; Francisco Javier Mesas-Carrascosa; Alfonso García-Ferrer; Fernando Juan Pérez-Porras. 2018. "Reconstruction of extreme topography from UAV structure from motion photogrammetry." Measurement 121, no. : 127-138.

Journal article
Published: 17 April 2018 in Remote Sensing
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The development of lightweight sensors compatible with mini unmanned aerial vehicles (UAVs) has expanded the agronomical applications of remote sensing. Of particular interest in this paper are thermal sensors based on lightweight microbolometer technology. These are mainly used to assess crop water stress with thermal images where an accuracy greater than 1 °C is necessary. However, these sensors lack precise temperature control, resulting in thermal drift during image acquisition that requires correction. Currently, there are several strategies to manage thermal drift effect. However, these strategies reduce useful flight time over crops due to the additional in-flight calibration operations. This study presents a drift correction methodology for microbolometer sensors based on redundant information from multiple overlapping images. An empirical study was performed in an orchard of high-density hedgerow olive trees with flights at different times of the day. Six mathematical drift correction models were developed and assessed to explain and correct drift effect on thermal images. Using the proposed methodology, the resulting thermally corrected orthomosaics yielded a rate of error lower than 1° C compared to those where no drift correction was applied.

ACS Style

Francisco-Javier Mesas-Carrascosa; Fernando Pérez-Porras; Jose Emilio Meroño De Larriva; Carlos Mena Frau; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Martínez-Carricondo; Alfonso García-Ferrer. Drift Correction of Lightweight Microbolometer Thermal Sensors On-Board Unmanned Aerial Vehicles. Remote Sensing 2018, 10, 615 .

AMA Style

Francisco-Javier Mesas-Carrascosa, Fernando Pérez-Porras, Jose Emilio Meroño De Larriva, Carlos Mena Frau, Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Patricio Martínez-Carricondo, Alfonso García-Ferrer. Drift Correction of Lightweight Microbolometer Thermal Sensors On-Board Unmanned Aerial Vehicles. Remote Sensing. 2018; 10 (4):615.

Chicago/Turabian Style

Francisco-Javier Mesas-Carrascosa; Fernando Pérez-Porras; Jose Emilio Meroño De Larriva; Carlos Mena Frau; Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Martínez-Carricondo; Alfonso García-Ferrer. 2018. "Drift Correction of Lightweight Microbolometer Thermal Sensors On-Board Unmanned Aerial Vehicles." Remote Sensing 10, no. 4: 615.

Journal article
Published: 01 May 2017 in Journal of Surveying Engineering
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This paper explores the influence of flight altitude, terrain morphology, and the number of ground control points (GCPs) on digital surface model (DSM) and orthoimage accuracies obtained with unmanned aerial vehicle (UAV) photogrammetry. For this study, 60 photogrammetric projects were carried out considering five terrain morphologies, four flight altitudes (i.e., 50, 80, 100, and 120 m), and three different numbers of GCPs (i.e., 3, 5, and 10). The UAV was a rotatory wing platform with eight motors, and the sensor was a nonmetric mirrorless reflex camera. The root-mean-square error (RMSE) was used to assess the accuracy of the DSM (Z component) and orthophotos (X, Y, and XY components RMSEX, RMSEY, and RMSEXY, respectively). The results show that RMSEX, RMSEY, and RMSEXY were not influenced by flight altitude or terrain morphology. For horizontal accuracy, differences between terrain morphologies were observed only when 5 or 10 GCPs were used, which were the best accuracies for the flattest morphologies. Nevertheless, the number of GCPs influenced the horizontal accuracy; as the number of GCPs increased, the accuracy improved. Vertical accuracy was not influenced by terrain morphology, but both flight altitude and the number of GCPs had significant influences on RMSEZ; as the number of GCPs increased, the accuracy improved. Regarding flight altitude, vertical accuracy decreased as flight altitude increased. The most accurate combination of flight altitude and number of GCPs was 50 m and 10 GCPs, respectively, which yielded RMSEX, RMSEY, RMSEXY, and RMSEZ values equal to 0.038, 0.035, 0.053, and 0.049 m, respectively. In view of these results, the map scale according to the legacy American Society for Photogrammetry and Remote Sensing map standard of 1990 will be approximately 1:150, and an equivalent contour interval of 0.150 m is sufficient for most civil engineering projects.

ACS Style

Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo. Accuracy of Digital Surface Models and Orthophotos Derived from Unmanned Aerial Vehicle Photogrammetry. Journal of Surveying Engineering 2017, 143, 04016025 .

AMA Style

Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Patricio Jesús Martínez Carricondo. Accuracy of Digital Surface Models and Orthophotos Derived from Unmanned Aerial Vehicle Photogrammetry. Journal of Surveying Engineering. 2017; 143 (2):04016025.

Chicago/Turabian Style

Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo. 2017. "Accuracy of Digital Surface Models and Orthophotos Derived from Unmanned Aerial Vehicle Photogrammetry." Journal of Surveying Engineering 143, no. 2: 04016025.

Journal article
Published: 01 February 2017 in Measurement
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Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo. Assessment of photogrammetric mapping accuracy based on variation ground control points number using unmanned aerial vehicle. Measurement 2017, 98, 221 -227.

AMA Style

Francisco Agüera-Vega, Fernando Carvajal-Ramírez, Patricio Jesús Martínez Carricondo. Assessment of photogrammetric mapping accuracy based on variation ground control points number using unmanned aerial vehicle. Measurement. 2017; 98 ():221-227.

Chicago/Turabian Style

Francisco Agüera-Vega; Fernando Carvajal-Ramírez; Patricio Jesús Martínez Carricondo. 2017. "Assessment of photogrammetric mapping accuracy based on variation ground control points number using unmanned aerial vehicle." Measurement 98, no. : 221-227.

Journal article
Published: 15 July 2016 in Environmental Progress & Sustainable Energy
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The agricultural system in south-eastern Spain is based on intensive horticulture in greenhouses. Public and private organizations have spent substantial resources on optimizing irrigation, due to the scant annual precipitation (close to 250 mm). In order to preserve natural water resources, avoiding overexploitation and salinization aquifers, the water loss has to be minimized. Farmers save water in irrigation reservoirs, which are open to the atmosphere most of the time. In this work, the loss to evaporation from open water reservoirs was estimated in a typical agricultural greenhouse area in Almeria province, south-eastern Spain. The data source was both a high-resolution satellite image, and a set of climatic data from the Agro-climatic Information Network of Andalusia (AINA) and from a Class-A pan evaporimeter. The image was used for detecting and delineating open water bodies applying a supervised classification algorithm based on an artificial neural network. The climatic data were used to estimate the distribution of monthly evaporation. It was concluded that irrigation water reservoirs can evaporate 3.76% of the input water used for crops. If all of the water bodies were covered with shade materials and if the precipitation intercepted by the roofs of greenhouses were saved in the irrigation water reservoirs, 49.87% of water annually consumed by greenhouse crops could be saved. © 2016 American Institute of Chemical Engineers Environ Prog, 2016

ACS Style

F. Carvajal; F. Agüera; Julián Sánchez-Hermosilla; Fernando Carvajal-Ramírez. Estimating the evaporation from irrigation reservoirs of greenhouses using satellite imagery. Environmental Progress & Sustainable Energy 2016, 35, 1750 -1757.

AMA Style

F. Carvajal, F. Agüera, Julián Sánchez-Hermosilla, Fernando Carvajal-Ramírez. Estimating the evaporation from irrigation reservoirs of greenhouses using satellite imagery. Environmental Progress & Sustainable Energy. 2016; 35 (6):1750-1757.

Chicago/Turabian Style

F. Carvajal; F. Agüera; Julián Sánchez-Hermosilla; Fernando Carvajal-Ramírez. 2016. "Estimating the evaporation from irrigation reservoirs of greenhouses using satellite imagery." Environmental Progress & Sustainable Energy 35, no. 6: 1750-1757.

Journal article
Published: 01 July 2016 in Journal of Applied Remote Sensing
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. The morphology of road cut slopes, such as length and high slopes, is one of the most prevalent causes of landslides and terrain stability troubles. Digital elevation models (DEMs) and orthoimages are used for land management purposes. Two flights with different orientations with respect to the target surface were planned, and four photogrammetric projects were carried out during these flights to study the image orientation effects. Orthogonal images oriented to the cut slope with only sidelaps were compared to the classical vertical orientation, with sidelapping, endlapping, and both types of overlapping simultaneously. DEM and orthoimages obtained from the orthogonal project showed smaller errors than those obtained from the other three photogrammetric projects, with the first one being much easier to manage. One additional flight and six photogrammetric projects were used to establish an objective criterion to locate the three ground control points for georeferencing and rectification DEMs and orthoimages. All possible sources of errors were evaluated in the DEMs and orthoimages.

ACS Style

Fernando Carvajal-Ramírez; Francisco Agüera-Vega; Patricio Jesús Martínez Carricondo. Effects of image orientation and ground control points distribution on unmanned aerial vehicle photogrammetry projects on a road cut slope. Journal of Applied Remote Sensing 2016, 10, 34004 .

AMA Style

Fernando Carvajal-Ramírez, Francisco Agüera-Vega, Patricio Jesús Martínez Carricondo. Effects of image orientation and ground control points distribution on unmanned aerial vehicle photogrammetry projects on a road cut slope. Journal of Applied Remote Sensing. 2016; 10 (3):34004.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; Francisco Agüera-Vega; Patricio Jesús Martínez Carricondo. 2016. "Effects of image orientation and ground control points distribution on unmanned aerial vehicle photogrammetry projects on a road cut slope." Journal of Applied Remote Sensing 10, no. 3: 34004.

Journal article
Published: 01 April 2015 in Biosystems Engineering
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The objective of this study is to determine the capability of an unmanned aerial vehicle system carrying a multispectral sensor to acquire multitemporal images during the growing season of a sunflower crop. Measurements were made at different times of the day and with different resolutions to estimate the normalised difference vegetation index (NDVI) and study its relationship with several indices related to crop status with the aim of generating useful information for application to precision agriculture techniques. NDVI was calculated from images acquired on four different dates during the cropping season. On two of these dates, two images were acquired to determine how the time of day when the images were taken influences NDVI value. To study the influence of image resolution on NDVI, the original images were resampled to 30 × 30 and 100 × 100 cm pixel sizes. The results showed that the linear regressions between NDVI and grain yield, aerial biomass and nitrogen content in the biomass were significant at the 99% confidence level, except during very early growth stages, whereas the time of day when the images were acquired, the classification process, and image resolution had no effect on the results. The methodology provides information that is related to crop yield from the very early stages of growth and its spatial variability within the crop field to be harvested, which can subsequently be used to prescribe the most appropriate management strategy on a site-specific basis.This work was supported by grant P08-TEP-3870 from CICE-Junta de Andalucía (Spain) and was co-financed with European Union FEDER funds.Peer reviewe

ACS Style

Francisco Agüera Vega; Fernando Carvajal-Ramírez; Mónica Pérez-Saiz; Francisco Orgaz Rosúa. Multi-temporal imaging using an unmanned aerial vehicle for monitoring a sunflower crop. Biosystems Engineering 2015, 132, 19 -27.

AMA Style

Francisco Agüera Vega, Fernando Carvajal-Ramírez, Mónica Pérez-Saiz, Francisco Orgaz Rosúa. Multi-temporal imaging using an unmanned aerial vehicle for monitoring a sunflower crop. Biosystems Engineering. 2015; 132 ():19-27.

Chicago/Turabian Style

Francisco Agüera Vega; Fernando Carvajal-Ramírez; Mónica Pérez-Saiz; Francisco Orgaz Rosúa. 2015. "Multi-temporal imaging using an unmanned aerial vehicle for monitoring a sunflower crop." Biosystems Engineering 132, no. : 19-27.

Journal article
Published: 01 January 2014 in Agricultural Water Management
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Fernando Carvajal-Ramírez; F. Agüera; Julián Sánchez-Hermosilla. Water balance in artificial on-farm agricultural water reservoirs for the irrigation of intensive greenhouse crops. Agricultural Water Management 2014, 131, 146 -155.

AMA Style

Fernando Carvajal-Ramírez, F. Agüera, Julián Sánchez-Hermosilla. Water balance in artificial on-farm agricultural water reservoirs for the irrigation of intensive greenhouse crops. Agricultural Water Management. 2014; 131 ():146-155.

Chicago/Turabian Style

Fernando Carvajal-Ramírez; F. Agüera; Julián Sánchez-Hermosilla. 2014. "Water balance in artificial on-farm agricultural water reservoirs for the irrigation of intensive greenhouse crops." Agricultural Water Management 131, no. : 146-155.

Journal article
Published: 01 December 2013 in Crop Protection
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Julián Sánchez-Hermosilla; Francisco Páez; Víctor J. Rincón; Fernando Carvajal. Evaluation of the effect of spray pressure in hand-held sprayers in a greenhouse tomato crop. Crop Protection 2013, 54, 121 -125.

AMA Style

Julián Sánchez-Hermosilla, Francisco Páez, Víctor J. Rincón, Fernando Carvajal. Evaluation of the effect of spray pressure in hand-held sprayers in a greenhouse tomato crop. Crop Protection. 2013; 54 ():121-125.

Chicago/Turabian Style

Julián Sánchez-Hermosilla; Francisco Páez; Víctor J. Rincón; Fernando Carvajal. 2013. "Evaluation of the effect of spray pressure in hand-held sprayers in a greenhouse tomato crop." Crop Protection 54, no. : 121-125.