Consumer-grade Digital Camera Research Articles

Monitoring plant condition and phenology using infrared sensitive consumer grade digital cameras

Consumer-grade digital cameras are recognized as a cost-effective method of monitoring plant health and phenology. The capacity to use these cameras to produce time series information contributes to a better understanding of relationships between environmental conditions, vegetation health, and productivity. In this study we evaluate the use of consumer grade digital cameras modified to capture infrared wavelengths for monitoring vegetation. The use of infrared imagery is very common in satellite remote sensing, while most current near sensing studies are limited to visible wavelengths only. The use of infrared-visible observations is theoretically superior over the use of just visible observation due to the strong contrast between infrared and visible reflection of vegetation, the high correlation of the three visible bands and the possibilities to use spectral indices like the Normalized Difference Vegetation Index.This paper presents two experiments: the first study compares infrared modified and true color cameras to detect seasonal development of understory plants species in a forest; the second is aimed at evaluation of spectrometer and camera data collected during a laboratory plant stress experiment. The main goal of the experiments is to evaluate the utility of infrared modified cameras for the monitoring of plant health and phenology.Results show that infrared converted cameras perform less than standard color cameras in a monitoring setting. Comparison of the infrared camera response to spectrometer data points at limits in dynamic range, and poor band separation as the main weaknesses of converted consumer cameras. Our results support the use of standard color cameras as simple and affordable tools for the monitoring of plant stress and phenology.

Gigapixel optical microscopy for meteorite characterization

We present an automated microscopy system for the optical characterization of meteorite thin sections. The system employs focus-stacking and high-dynamic range imaging to facilitate high-contrast and unpolished samples. Images are acquired at ∼385 nm/pixel and automatically stitched together to create a billion-pixel image for a typical ∼1 cm2 thin section. This image can be viewed in a web browser (with smooth panning and zooming) using a free browser plugin. The software we created to acquire and assemble these images is made freely available for others to create a similar system. Large optical digital images of meteorite sections make it possible to collaboratively inspect and characterize the sample by using the web browser interface as a “virtual microscope”. The system can be employed on any optical microscope with a computerized stage and consumer-grade digital camera, and can be used in a wide range of applications.

Kite aerial photography for low-cost, ultra-high spatial resolution multi-spectral mapping of intertidal landscapes.

Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time that could complement field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at limited spatial and temporal resolutions and relatively high costs for small-scale environmental science and ecologically-focussed studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric/mapping procedure that was developed for constructing high-resolution, three-dimensional, multi-spectral terrain models of intertidal rocky shores. The processing procedure uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine imagery at visible and near-infrared wavelengths and topographic information at sub-centimeter resolutions over an intertidal shoreline 200 m long, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rocky shore at Jervis Bay, New South Wales, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales.

Classifying hidden colors behind an opaque layer with the acoustically modulated laser speckle contrast technique

The acoustically modulated laser speckle contrast technique has been employed to quantify and classify 25 colors (made up by different percentages of the two base colors cyan and magenta) hidden behind a 5 mm thick opaque layer with 0.24% transmittance. The main components included two He-Ne lasers (543 and 633 nm), a consumer grade digital camera (Nikon 1 J1), focusing optics and a loudspeaker. The camera captured the laser speckle patterns with the sound on and off, respectively, from which the speckle contrast differences were calculated and used in a nearest neighbor classification algorithm. The classification accuracy was between 55% and 88% depending on the underlying reflectance of all the colors to be classified.

QUALITY OF 3D POINT CLOUDS FROM HIGHLY OVERLAPPING UAV IMAGERY

Abstract. UAVs are becoming standard platforms for photogrammetric data capture especially while aiming at large scale aerial mapping for areas of limited extent. Such applications especially benefit from the very reasonable price of a small light UAS including control system and standard consumer grade digital camera, which is some orders of magnitude lower compared to digital photogrammetric systems. Within the paper the capability of UAV-based data collection will be evaluated for two different consumer camera systems and compared to an aerial survey with a state-of-the-art digital airborne camera system. During this evaluation, the quality of 3D point clouds generated by dense multiple image matching will be used as a benchmark. Also due to recent software developments such point clouds can be generated at a resolution similar to the ground sampling distance of the available imagery and are used for an increasing number of applications. Usually, image matching benefits from the good images quality as provided from digital airborne camera systems, which is frequently not available from the low-cost sensor components used for UAV image collection. Within the paper an investigation on UAV-based 3D data capture will be presented. For this purpose dense 3D point clouds are generated for a test area from three different platforms: first a UAV with a light weight compact camera, second a system using a system camera and finally a medium-format airborne digital camera system. Despite the considerable differences in system costs, suitable results can be derived from all data, especially if large redundancy is available such highly overlapping image blocks are not only beneficial during georeferencing, but are especially advantageous while aiming at a dense and accurate image based 3D surface reconstruction.

Digital Camera Nikon D300 in Support of High Mountain Studies in the Langtang Valley, Central Himalaya, Nepal

This paper describes two different mapping projects in the upper Langtang Valley, Central Himalaya, Nepal, applying close-range photogrammetry using a non-metric consumer-grade digital camera Nikon D300. Data acquisition (terrestrial photographs, and additional handheld GPS and laser distance measurements) was carried out during a field campaign in April 2010. The first mapping project aimed to document the present extent of the glacier tongue of Kyimoshung Glacier, Langtang Himal, and to compare this glacial stage with an earlier one (1992). The second mapping project intended to produce a large-scale map of Kyanjin Gompa for socio-economic studies. Kyanjin Gompa is a small settlement with a fast growing tourism infrastructure. Photogrammetric work was supported by commercial software, such as ImageStation of Intergraph and/or PhotoModeler. The results obtained are presented graphically using maps and numerically.

The utility of low-cost photogrammetry for stiffness analysis and finite-element validation of wood with knots in bending

This article presents the capabilities of low-cost photogrammetry as a tool for stiffness analysis and finite-element (FE) validation in conventional bending tests of structural timber that contains knots. The accuracy offered by three consumer-grade digital cameras with a resolution of 10 megapixels was 1/6200, which did not allow for the evaluation of the stresses or strains in a multiaxial stress field, but provided a thorough contrast of the 3D nodal displacements, showing the distortion of knots in the modulus of elasticity (MOE), so that the heterogeneous stiffness of this natural material could be measured and accounted for. This allowed a more precise determination of the wood stiffness in bending, and a novel procedure for the estimation of a Clear MOE related to the defect-free areas, an MOE in Knots related to the distorted regions, and a Global MOE which encompasses both was developed. The proposed method can be applied to conventional mechanical tests. In addition, other interesting possibilities for FE validation and monitoring were obtained. The case study demonstrates how, with a very small investment, an FE model that simulates the influence of knots in bending could be accurately validated with many fewer specimens, and how the predictions of displacements could be improved by up to 49% using the Clear MOE measured by means of the photogrammetry rather than the conventional MOE without shearing strain. ► Low-cost photogrammetry used to determine mechanical properties of timber pieces. ► Novel procedure for obtaining more precise wood stiffness measurement is proposed. ► Predicted stiffness using proposed numerical simulations improved by up to 49%

Assessment of Liquid Saturations in Sand by Image Analysis

This research investigates the relationship between optical density and liquid saturations in unsaturated sand using multispectral image analysis technique. The tested liquids are water, diesel, and parafin liquid. The experiments are performed on two-fluid phase systems (water-air, diesel-air, and parafin liquid-air) and three-fluid phase systems (diesel-water-air and parafin liquid-water-air). Water is dyed with Brilliant Blue FCF, whereas diesel and parafin liquid are dyed with Red Sudan III. Using consumer-grade digital cameras, two images of sand specimens with various liquid saturations are taken with two different band-pass filters. The analysis results show that, for the sand and investigated fluids, the optical density defined for the reflected luminous intensity is a linear function of the degrees of fluid saturation for each spectral band and for any two- and three-fluid phase systems.

LANDSLIDE MAPPING USING IMAGERY ACQUIRED BY A FIXED-WING UAV

Abstract. In Taiwan, the average annual rainfall is about 2,500 mm, about three times the world average. Hill slopes where are mostly under meta-stable conditions due to fragmented surface materials can easily be disturbed by heavy typhoon rainfall and/or earthquakes, resulting in landslides and debris flows. Thus, an efficient data acquisition and disaster surveying method is critical for decision making. Comparing with satellite and airplane, the unmanned aerial vehicle (UAV) is a portable and dynamic platform for data acquisition. In particularly when a small target area is required. In this study, a fixed-wing UAV that equipped with a consumer grade digital camera, i.e. Canon EOS 450D, a flight control computer, a Garmin GPS receiver and an attitude heading reference system (AHRS) are proposed. The adopted UAV has about two hours flight duration time with a flight control range of 20 km and has a payload of 3 kg, which is suitable for a medium scale mapping and surveying mission. In the paper, a test area with 21.3 km2 in size containing hundreds of landslides induced by Typhoon Morakot is used for landslides mapping. The flight height is around 1,400 meters and the ground sampling distance of the acquired imagery is about 17 cm. The aerial triangulation, ortho-image generation and mosaicking are applied to the acquired images in advance. An automatic landslides detection algorithm is proposed based on the object-based image analysis (OBIA) technique. The color ortho-image and a digital elevation model (DEM) are used. The ortho-images before and after typhoon are utilized to estimate new landslide regions. Experimental results show that the developed algorithm can achieve a producer's accuracy up to 91%, user's accuracy 84%, and a Kappa index of 0.87. It demonstrates the feasibility of the landslide detection algorithm and the applicability of a fixed-wing UAV for landslide mapping.

‘Structure-from-Motion’ photogrammetry: A low-cost, effective tool for geoscience applications

High-resolution topographic surveying is traditionally associated with high capital and logistical costs, so that data acquisition is often passed on to specialist third party organisations. The high costs of data collection are, for many applications in the earth sciences, exacerbated by the remoteness and inaccessibility of many field sites, rendering cheaper, more portable surveying platforms (i.e. terrestrial laser scanning or GPS) impractical. This paper outlines a revolutionary, low-cost, user-friendly photogrammetric technique for obtaining high-resolution datasets at a range of scales, termed ‘Structure-from-Motion’ (SfM). Traditional softcopy photogrammetric methods require the 3-D location and pose of the camera(s), or the 3-D location of ground control points to be known to facilitate scene triangulation and reconstruction. In contrast, the SfM method solves the camera pose and scene geometry simultaneously and automatically, using a highly redundant bundle adjustment based on matching features in multiple overlapping, offset images. A comprehensive introduction to the technique is presented, followed by an outline of the methods used to create high-resolution digital elevation models (DEMs) from extensive photosets obtained using a consumer-grade digital camera. As an initial appraisal of the technique, an SfM-derived DEM is compared directly with a similar model obtained using terrestrial laser scanning. This intercomparison reveals that decimetre-scale vertical accuracy can be achieved using SfM even for sites with complex topography and a range of land-covers. Example applications of SfM are presented for three contrasting landforms across a range of scales including; an exposed rocky coastal cliff; a breached moraine-dam complex; and a glacially-sculpted bedrock ridge. The SfM technique represents a major advancement in the field of photogrammetry for geoscience applications. Our results and experiences indicate SfM is an inexpensive, effective, and flexible approach to capturing complex topography.

LOW-COST, ULTRA-HIGH SPATIAL AND TEMPORAL RESOLUTION MAPPING OF INTERTIDAL ROCK PLATFORMS

Abstract. Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time which could compliment field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at relatively course, sub-meter resolutions or with limited temporal resolutions and relatively high costs for small-scale environmental science and ecology studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric pipeline that was developed for constructing highresolution, 3D, photo-realistic terrain models of intertidal rocky shores. The processing pipeline uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine colour and topographic information at sub-centimeter resolutions over an area of approximately 100m, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rock platform at Cape Banks, Sydney, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales.

Multiview 3D reconstruction in geosciences

Multiview three-dimensional (3D) reconstruction is a technology that allows the creation of 3D models of a given scenario from a series of overlapping pictures taken using consumer-grade digital cameras. This type of 3D reconstruction is facilitated by freely available software, which does not require expert-level skills. This technology provides a 3D working environment, which integrates sample/field data visualization and measurement tools. In this study, we test the potential of this method for 3D reconstruction of decimeter-scale objects of geological interest. We generated 3D models of three different outcrops exposed in a marble quarry and two solids: a volcanic bomb and a stalagmite. Comparison of the models obtained in this study using the presented method with those obtained using a precise laser scanner shows that multiview 3D reconstruction yields models that present a root mean square error/average linear dimensions between 0.11 and 0.68%. Thus this technology turns out to be an extremely promising tool, which can be fruitfully applied in geosciences.

X-ray imaging using a consumer-grade digital camera

2 þ Computed radiography abstract The recent advancements in consumer-grade digital camera technology and the introduction of high- resolution, high sensitivity CsBr:Eu 2 þ storage phosphor imaging plates make possible a new cost- effective technique for X-ray imaging. The imaging plate is bathed with red stimulating light by high- intensity light-emitting diodes, and the photostimulated image is captured with a digital single-lens reflex (SLR) camera. A blue band-pass optical filter blocks the stimulating red light but transmits the blue photostimulated luminescence. Using a Canon D5 Mk II camera and an f1.4 wide-angle lens, the optical image of a 240 � 180 mm 2 Konica CsBr:Eu 2 þ imaging plate from a position 230 mm in front of the camera lens can be focussed so as to laterally fill the 35 � 23.3 mm 2 camera sensor, and recorded in 2808 � 1872 pixel elements, corresponding to an equivalent pixel size on the plate of 88 mm. The analogue-to-digital conversion from the camera electronics is 13 bits, but the dynamic range of the imaging system as a whole is limited in practice by noise to about 2.5 orders of magnitude. The modulation transfer function falls to 0.2 at a spatial frequency of 2.2 line pairs/mm. The limiting factor of the spatial resolution is light scattering in the plate rather than the camera optics. The limiting factors for signal-to-noise ratio are shot noise in the light, and dark noise in the CMOS sensor. Good quality images of high-contrast objects can be recorded with doses of approximately 1 mGy. The CsBr:Eu

Photogrammetry Assisted Measurement of Interstory Drift for Rapid Post-disaster Building Damage Reconnaissance

Timely and accurate evaluation of damage sustained by buildings after seismic events such as earthquakes or blasts is critical to determine the buildings’ safety and suitability for their future occupancy. Time used in conducting the evaluations substantially affects the duration for which the potentially damaged buildings remain unusable. The elapsed time may lead to direct economic losses to both public and private owners, and society at large. The presented research investigates the application of close-range photogrammetry surveying techniques and Augmented Reality (AR) visualization to design a semi-automated method for rapidly measuring structural damage induced in tall buildings by seismic events such as earthquakes or explosions. Close-range photogrammetry algorithms were designed to extract spatial information from photographic image data, and geometrically measure the horizontal drift (also called interstory drift) sustained at key floors along the edge of a damaged building. The measured drift can then be used to compute damage indices that correlate the drift to the building’s structural integrity and safety. In this research, the measurement accuracy of the calculated drift using photogrammetry principles is particularly studied. The experimental results achieved an acceptable and usable accuracy level of 5 mm using a consumer grade digital SLR camera, demonstrating the potential of photogrammetry assisted rapid measurement of earthquake-induced building damage. It is expected that in the future, as advances in optical-sensing and positioning technologies continue to make high-end cameras and measurement systems (GPS, compass) more affordable, higher accuracy will be practically achievable for further improvement in measurements using the proposed method.

Color image segmentation approach to monitor flowering in lesquerella

Abstract Lesquerella ( Lesquerella fendleri (Gray) Wats.) seed oil has been proposed as a petroleum alternative in the production of many industrial products, but several crop management and breeding challenges must be addressed before the crop will be grown commercially. Lesquerella canopies characteristically exhibit quite prominent and vibrant yellow flowers at anthesis, and remote detection of lesquerella flowering patterns can provide useful crop development information to aid management and breeding decisions. In the present study, we used a consumer-grade digital camera to collect images 2 m above lesquerella canopies throughout two growing seasons. Biomass samples within 0.125 m 2 areas were also regularly collected and processed to obtain flower numbers. Image processing algorithms were developed to extract information on lesquerella flower features from the images. Key features of the image processing approach included an image transformation to the hue, saturation, and intensity (HSI) color space and a Monte Carlo approach to address uncertainty in HSI parameters used for image segmentation. Flower numbers were estimated from image-based flower cover percentage with root mean squared errors that ranged from 159 to 194 flowers, which was better than the reported results for other studies with a similar objective. Attempts to resolve individual flowers were less successful due to the complexity of the flowering patterns within the image scenes. Digital imaging offers an inexpensive and quite practical means for remote monitoring of flowering patterns in lesquerella canopies.

Design and Development of a Multi-Purpose Low-Cost Hyperspectral Imaging System

Hyperspectral image analysis is gaining momentum in a wealth of natural resources and agricultural applications facilitated by the increased availability of low-cost imaging systems. In this study, we demonstrate the development of the Vegetation Mobile Mapping System (VMMS), a low-cost hyperspectral sensing system that is supported by consumer-grade digital camera(s). The system was developed using off-the-shelf imaging and navigation components mainly for ground-based applications. The system integrates a variety of components including timing and positioning GPS receivers and an Inertial Measurement Unit (IMU). The system was designed to be modular and interoperable allowing the imaging components to be used with different navigation systems. The technique used for synchronizing captured images with GPS time was presented. A relative radiometric calibration technique utilizing images of homogeneous targets to normalize pixel gain and offset parameters was used. An empirical spectral calibration method was used to assign wavelengths to image bands. Data acquisition parameters to achieve appropriate spatial coverage were presented. The system was tested in ground-based data collection and analysis experiments that included water quality and vegetation studies.

Camera-Variant Calibration and Sensor Modeling for Practical Photogrammetry in Archeological Sites

With the appearance of low-cost and high-resolution consumer-grade digital cameras, a practical three-dimensional (3D) measurement system using a consumer-grade digital camera is greatly anticipated in various fields. In these circumstances, the authors have been concentrating on developing a practical 3D measurement system that includes photogrammetric software called the Image Based Integrated Measurement (IBIM) system. The IBIM system device consists of full/half-mirrors, a consumer-grade digital camera, and a laser distance meter. The most remarkable advantage of the system is its ability to calculate exterior orientation parameters, interior orientation parameters, and pseudo ground control points (GCPs) without using scale bars or the GCPs in the object field. The system has the ability to calibrate multiple cameras of different resolutions using a camera-variant parameter set. However, there remains one issue that needs to be resolved before this system can be effectively used, namely, improvement of the system which does not depend on the IBIM system device. With this motive, a practical photogrammetry method using a consumer-grade digital cameras and a hand-held laser distance meter is proposed. To test our proposed method, the bundle of distances from the center camera position to the feature points in the object field were measured individually at archaeological sites in Greece. In order to evaluate the possibility and practicability of the proposed photogrammetry method, this paper describes and evaluates the camera calibration techniques using images from multiple cameras of different resolutions and a bundle of distances.

Probing Planck's law at home

We report on the physics around an incandescent lamp. Using a consumer-grade digital camera, we combine electrical and optical measurements to explore Planck's law of black-body radiation. This simple teaching experiment is successfully used to measure both Stefan's and Planck's constants. Our measurements lead to a strikingly accurate value for Planck's constant: h = 6.7 ± 0.4 × 10−34 kg m2 s−1. A digital camera is thus sufficiently good equipment to measure a constant directly related to quantum mechanics. The simplicity of the proposed experiments makes this paper appropriate for undergraduate students interested in the experimental aspects of fundamental physics.

A simple methodology for recording petroglyphs using low-cost digital image correlation photogrammetry and consumer-grade digital cameras

In the present study a simple method is described for obtaining 3D digital models of petroglyphs of different sizes and characteristics and its usefulness, in the study of this cultural heritage, is evaluated. For this research we used low-cost photogrammetric software and consumer-grade digital cameras, without any other surveying techniques. In order to test this methodology, three field research studies were carried out in Galicia (Spain). By means of the proposed methodology, 3D digital models are obtained using basic equipment and its accuracy can be evaluated easily with the help of a calliper. Given the possibilities of analysis that they offer, 3D digital models can substantially assist in the study, comprehension and interpretation of petroglyphs by archaeologists, conservationists and rock-site managers. Low-cost digital image correlation photogrammetry is a simple and very versatile technique in its application to the documentation, analysis and diffusion of this cultural heritage. As has occurred with other 3D modelling techniques, it not only complements traditional techniques but can indeed substitute them, owing fundamentally to its simplicity and the interactive character of the 3D digital models, that can easily be inserted in the web.

A Fiber-Optic Fluorescence Microscope Using a Consumer-Grade Digital Camera for In Vivo Cellular Imaging

BackgroundEarly detection is an essential component of cancer management. Unfortunately, visual examination can often be unreliable, and many settings lack the financial capital and infrastructure to operate PET, CT, and MRI systems. Moreover, the infrastructure and expense associated with surgical biopsy and microscopy are a challenge to establishing cancer screening/early detection programs in low-resource settings. Improvements in performance and declining costs have led to the availability of optoelectronic components, which can be used to develop low-cost diagnostic imaging devices for use at the point-of-care. Here, we demonstrate a fiber-optic fluorescence microscope using a consumer-grade camera for in vivo cellular imaging.MethodsThe fiber-optic fluorescence microscope includes an LED light, an objective lens, a fiber-optic bundle, and a consumer-grade digital camera. The system was used to image an oral cancer cell line labeled with 0.01% proflavine. A human tissue specimen was imaged following surgical resection, enabling dysplastic and cancerous regions to be evaluated. The oral mucosa of a healthy human subject was imaged in vivo, following topical application of 0.01% proflavine.FindingsThe fiber-optic microscope resolved individual nuclei in all specimens and tissues imaged. This capability allowed qualitative and quantitative differences between normal and precancerous or cancerous tissues to be identified. The optical efficiency of the system permitted imaging of the human oral mucosa in real time.ConclusionOur results indicate this device as a useful tool to assist in the identification of early neoplastic changes in epithelial tissues. This portable, inexpensive unit may be particularly appropriate for use at the point-of-care in low-resource settings.