Digital Aerial Photographs Research Articles

Estimation of Forest Aboveground Biomass and Leaf Area Index Based on Digital Aerial Photograph Data in Northeast China

Forest aboveground biomass (AGB) and leaf area index (LAI) are two important parameters for evaluating forest growth and health. It is of great significance to estimate AGB and LAI accurately using remote sensing technology. Considering the temporal resolution and data acquisition costs, digital aerial photographs (DAPs) from a digital camera mounted on an unmanned aerial vehicle or light, small aircraft have been widely used in forest inventory. In this study, the aerial photograph data was acquired on 5 and 9 June, 2017 by a Hasselblad60 digital camera of the CAF-LiCHy system in a Y-5 aircraft in the Mengjiagang forest farm of Northeast China, and the digital orthophoto mosaic (DOM) and photogrammetric point cloud (PPC) were generated from an aerial overlap photograph. Forest red-green-blue (RGB) vegetation indices and textural factors were extracted from the DOM. Forest vertical structure features and canopy cover were extracted from normalized PPC. Regression analysis was carried out considering only DOM data, only PPC data, and a combination of both. A recursive feature elimination (RFE) method using a random forest was used for variable selection. Four different machine-learning (ML) algorithms (random forest, k-nearest neighbor, Cubist and supporting vector machine) were used to build regression models. Experimental results showed that PPC data alone could estimate AGB, and DOM data alone could estimate LAI with relatively high accuracy. The combination of features from DOM and PPC data was the most effective, in all the experiments considered, for the estimation of AGB and LAI. The results showed that the height and coverage variables of PPC, texture mean value, and the visible differential vegetation index (VDVI) of the DOM are significantly related to the estimated AGB (R2 = 0.73, RMSE = 20 t/ha). The results also showed that the canopy cover of PPC and green red ratio index (GRRI) of DOM are the most strongly related to the estimated LAI, and the height and coverage variables of PPC, the texture mean value and visible atmospherically resistant index (VARI), and the VDVI of DOM followed (R2 = 0.79, RMSE = 0.48).

Using aerial photography to estimate wood suitable for charcoal in managed oak forests

Mexican oak forests (genus Quercus) are frequently used for traditional charcoal production. Appropriate management programs are needed to ensure their long-term use, while conserving the biodiversity and ecosystem services, and associated benefits. A key variable needed to design these programs is the spatial distribution of standing woody biomass. A state-of-the-art methodology using small format aerial photographs was developed to estimate the total aboveground biomass (AGB) and aboveground woody biomass suitable for charcoal making (WSC) in intensively managed oak forests. We used tree crown area (CAap) measurements from very high-resolution (30 cm) orthorectified small format digital aerial photographs as the predictive variable. The CAap accuracy was validated using field measurements of the crown area (CAf). Allometric relationships between: (a) CAap versus AGB, and (b) CAap versus WSC had a high significance level (R 2 > 0.91, p < 0.0001). This approach shows that it is possible to obtain sound biomass estimates as a function of the crown area derived from digital small format aerial photographs.

Potential of Retrofitting Sustainable Urban Drainage Systems Using an Integrated Geographical Information System-Remote Sensing Based Approach

Many urban areas are located in flat, low lying coastal areas with outdated, inadequate sewer networks. Flooding is a major problem in such urban areas worldwide with consequent severe economic impacts. Many current monitoring approaches are based on ground-based visual mapping and household flooding surveys which are expensive, time-consuming and often produce inaccurate and spatially incomplete results. Low-cost methodologies that can rapidly assess the scale and identify the reasons causing these flood events at minimal cost are therefore urgently required. This study has evaluated the capability of an integrated remote sensing and geographical information system based approach to provide complete coverage of the critical information on the spatial extent of flooding and flood water volumes rapidly and at low cost. Airborne and Terrestrial LiDAR datasets were combined with digital aerial photography, flood assessment surveys, and maps of housing, infrastructure and the sewer network to provide an enhanced understanding of the sources and pathways of the flood water runoff, accurate quantification of the water volumes associated with each flooding event and the identification of locations and size of potential retrofit Sustainable Urban Drainage systems.

Landscape dynamics of Mediterranean montane grasslands over 60 years and implications for habitats conservation. A case study in the northern Apennines (Italy)

Widespread trends of abandonment have strongly affected Mediterranean mountains after the Second World War, triggering spontaneous recolonisation of forests. A diachronic analysis of the landscape in a Natura 2000 site (Tuscany, Italy) was carried out using digital aerial photographs (1954, 2013) and a GIS-based methodology, focusing on territories above 1300 m a.s.l. The detected variations of total areas, patch shape, patch dimensions and selected metrics showed a notable shift of the vegetation towards woody types and a drastic reduction of open grasslands, some with high conservation value, accompanied by a strong increase in patch number, surface and edge. A decrease of SDI and SEI diversity indices was also observed. Considering that fragmentation is one of the main causes threatening habitats and species, our results point out a clear necessity for a monitoring programme and suitable actions aimed at improving the status of biodiversity-rich montane grasslands.

Method of significant structural characteristics of transformant coding for increase in integrity of aerial photographs in system of air reconnaissance

In article the topical issues connected with processing of digital aerial photographs in system of air reconnaissance are considered. The received digital aerial photographs, by means of onboard pilotless complexes in the course of conducting air reconnaissance, differ in high degree of a saturation in fine details, having significant amounts of information reaching about 100 Mbit. Therefore, there are questions, connected not only with timeliness of transfer of aerial photographs to the center of information processing, but also need of ensuring the required level of preservation of key signs for further decryption of aerial photographs. It is offered to carry out previously processing of aerial photographs onboard that will lead to decrease in information intensity on condition of saving information, semantic significant for decryption. The method of coding of blocks of an aerial photograph taking into account degree of a semantic saturation of each block is developed for onboard pilotless complexes of air reconnaissance. Based on formation of the sequence of significant two-element vectors for the structurized transformants. Use of a method will allow to reduce the volume of the processed and transmitted data that will bring to increase in integrity of information in system of air reconnaissance.

Novel fusion approach on automatic object extraction from spatial data: case study Worldview-2 and TOPO5000

The automatic extraction of information content from remotely sensed data is always challenging. We suggest a novel fusion approach to improve the extraction of this information from mono-satellite images. A Worldview-2 (WV-2) pan-sharpened image and a 1/5000-scaled topographic vector map (TOPO5000) were used as the sample data. Firstly, the buildings and roads were manually extracted from WV-2 to point out the maximum extractable information content. Subsequently, object-based automatic extractions were performed. After achieving two-dimensional results, a normalized digital surface model (nDSM) was generated from the underlying digital aerial photos of TOPO5000, and the automatic extraction was repeated by fusion with the nDSM to include individual object heights as an additional band for classification. The contribution was tested by precision, completeness and overall quality. Novel fusion technique increased the success of automatic extraction by 7% for the number of buildings and by 23% for the length of roads.

Application of inertial measuring unit in air navigation for ALS and DAP

This article describes the inertial measuring device IMU, as well as its use in airborne laser scanning and digital aerial photography. This device is used during the operation of a scanning unit and an aerial photo camera. The structure of an additional connection for a digital video camera is proposed, which will record video together with the GPS and IMU data stream. Also, conclusions are given about the quality of output data that affect a final product in engineering surveys.

Angola Coastal Mapping and Tactics for Oil Spill Response

ABSTRACT The Angolan oil and gas industry workgroup (ACEPA-Associação das Companhias de Exploração e Produção de Angola) continues to collaborate in the development and completion of oil spill response initiatives as responsible operators and committed participants in the IMO-IPIECA Global Initiative for West, Central and Southern Africa (GI WACAF). Between 2012–2015, a comprehensive program of oil spill response planning, geodatabase development, mapping, and guides were completed for the entire coast of Angola. Low altitude aerial video surveys that combine oblique imagery and a verbal commentary record were recorded as the foundation for mapping coastal sensitivities, ESI characterization, shore zone and backshore operational definition, and shoreline segmentation. Other information added to the coastal geodatabase includes operational and logistical considerations such as land access and boat launch locations, proposed sites for staging, holding of temporary wastes, industrial and human use (fishing, recreational), and nearshore access constraints. A key aspect of the shoreline mapping effort was to build the information into a stand-alone pre-shoreline cleanup assessment technique (SCAT)-database that provides layered information for each of the 1999 shoreline segments. Digital video and high-resolution oblique aerial photos for 2400 km of coastline are geo-referenced and integrated into the GIS system with viewer software that allows the user to “fly” the shoreline. Shoreline attributes for biological, socioeconomic, and human use were used to rank 117 sensitive sites. The 45 highest priority sensitive sites were surveyed and detailed geographic response plans (GRPs) for site protection strategies and tactics were compiled into two atlases. The comprehensive coastal characterization, segmentation, and priority site protection plans provide the Angola government and oil industry with spill preparedness tools that are world-class.

Detección de árboles dañados por plaga en bosques de Abies religiosa en la Reserva de la Biosfera Mariposa Monarca, mediante fotografías aéreas infrarroja

Forest pests are pathogens that cause mechanical or physiological damage to trees, such as deformations, disrupted growth, weakening, or even death, leading to important ecological, economic and social impacts. This study focused on the development of a technique for the detection of forest pests using infrared aerial photography. The general reflectance characteristics of healthy and damaged leaves are currently well known; Reid (1987) already described these features, with a shift toward blue and a reduced infrared reflectance as the dominant effects. As the plant disease progresses, the above effects become more apparent. The use of infrared digital aerial photographs allowed to obtain VIR (visible + infrared) images with four bands and a resolution of approximately one meter per pixel. Trees with some degree of deterioration and even dead individuals were identified and located through visual interpretation.Color and infrared digital aerial photographs captured in March 2009 were used; two cameras were used: a Nikon D2X camera for the acquisition of images in the visible range (EV), and a Canon EOS Digital Rebel camera for infrared (IR) images. Once individual photographs were processed and organized, V and IR images were superimposed using the Photoshop editing program (Adobe™) Once composite V+IR (VIR) images were obtained, those covering the sampling area were selected and georeferenced. Rectified images were required to elaborate a mosaic encompassing the sampling area. The rectified images and the final mosaic had a spatial resolution of 90 centimeters per pixel.The detection technique was designed using three methodological approaches: automatic, semi-automatic and manual processes. The semi-automatic and automatic modalities correspond to an assisted and unassisted spectral classification, respectively, while the manual method consisted in the direct observation of the photographs processed. The technique developed used as basis the photographic mosaic of the sampling area.The unassisted and assisted spectral classification technique was carried out in the ERDAS Imagine image-processing software package. For the unassisted classification, tests were carried out considering various numbers of categories: 5, 10 and 15; the assisted classification included the spectral properties of each category used for the partition to group images into five categories: healthy forest, diseased forest, Juniperus scrubland, bare soil and shaded areas.The accuracy of the technique for the detection of damaged trees was verified through field work, visiting different checkpoints where the health status of the tree was corroborated by direct observation and infrared photography at ground level.A representative sampling area of the A. religiosa forest was established in the Monarch Butterfly Biosphere Reserve (RBMM), sufficient to encompass the largest number of damaged trees, but not so large as to excessively prolong the information-processing phases and make field sampling unattainable.The analysis comprised an area of 1907 ha in Sierra Chincua, where the greatest affectation was observed in a core zone including 97 points (62%) with more than twice the density of individuals (11 trees/km2), relative to the buffer zone (4 trees/km2). This greater damage is the result of forest management policies, which have set no management (including sanitation) in the core zone.At the end of this research work, we concluded that digital aerial photographs proved useful for the detection of damaged trees in Abies religiosa forests of RBMM. It is possible to obtain multispectral images using a low-cost photographic technology that is relatively simple and widely available. Our study showed that the best method to detect damage in A. religiosa forests in RBMM is the visual interpretation of aerial photographs, yielding a detection efficiency of over 98%. The method used has a greater cost- effectiveness compared to helicopter overflight and field work. Likewise, the method developed in this research work is a contribution to the detection of forest pests.

3D Multi-view Stereo Modelling of an Open Mine Pit Using a Lightweight UAV

Digital elevation models have been evolved in decades, their resolution and accuracy have improved vividly. Geological, structural and geomorphological benefits of those high-quality digital elevation models enhanced the quality of the research and engineering and unfold the visibility of the data. Modern techniques such as laser scanners provide a quantum leap on digital modelling, however the cost of those methods limits their widespread usage. Improvements in stereo-photogrammetry did not decelerate. On the contrary, the evolution of Structure from Motion–Multi-view stereo-photogrammetry (SfM-MVS) method is accelerated by the continuous developments in digital photography and computer vision technologies. We have used a lightweight drone to acquire digital aerial photographs of an open mine pit for an ultimate purpose of modelling the terrain using SfM-MVS procedure. We have been able to derive a high resolution (0.3 m/pixel) DEM and a very high resolution (0.04 m/pixel) orthorectified aerial image. Both datasets are representing the topography with high sample point densities. Elevation model dataset has been compared with the regular topographic point measurements of the mine pit and the accuracy of the aerially derived model have been investigated. Sources of modelling errors, the effect of temporal physical changes in the terrain, effect and importance of geo-referencing have been discussed in detail. SfM-MVS is a cost-effective, rapid and promising technique for digital mapping, modelling and monitoring in various spatial scales of Geology.

Applying object-based image analysis and knowledge-based classification to ADS-40 digital aerial photographs to facilitate complex forest land cover classification

In general, considerable human and material resources are required for performing a forest inventory survey. Using remote sensing technologies to save forest inventory costs has thus become an important topic in forest inventory-related studies. Leica ADS-40 digital aerial photographs feature advantages such as high spatial resolution, high radiometric resolution, and a wealth of spectral information. As a result, they have been widely used to perform forest inventories. We classified ADS-40 digital aerial photographs according to the complex forest land cover types listed in the Fourth Forest Resource Survey in an effort to establish a classification method for categorizing ADS-40 digital aerial photographs. Subsequently, we classified the images using the knowledge-based classification method in combination with object-based analysis techniques, decision tree classification techniques, classification parameters such as object texture, shape, and spectral characteristics, a class-based classification method, and geographic information system mapping information. Finally, the results were compared with manually interpreted aerial photographs. Images were classified using a hierarchical classification method comprised of four classification levels (levels 1 to 4). The classification overall accuracy (OA) of levels 1 to 4 is within a range of 64.29% to 98.50%. The final result comparisons showed that the proposed classification method achieved an OA of 78.20% and a kappa coefficient of 0.7597. On the basis of the image classification results, classification errors occurred mostly in images of sunlit crowns because the image values for individual trees varied. Such a variance was caused by the crown structure and the incident angle of the sun. These errors lowered image classification accuracy and warrant further studies. This study corroborates the high feasibility for mapping complex forest land cover types using ADS-40 digital aerial photographs.

Mapping fire severity and fire extent in forest in Victoria for ecological and fuel outcomes

SummaryThis study shows how high‐resolution (~15 cm) simultaneous colour and infra‐red digital aerial photography can be used to map both fire severity and, particularly, fire extent, in forest in south‐eastern Australia. The results show that this methodology is capable of detecting and mapping burnt and unburnt edges under unaffected forest canopy (i.e. still green) – that is, revealing the mosaic of burnt and unburnt areas that often result from planned landscape burning under mild weather conditions (i.e. with little of the brownish canopy scorch that results from more intense bushfires). This has important implications for both fuel management and ecology. It can answer the basic questions of fire and biodiversity managers following planned burning –’how much of the planned area burnt, and, within the burnt area, what aspects were burnt, and how hot did they burn?’ The analysis of fire extent by aspect showed that about 80% of southern and eastern aspects remained unburnt during broadscale autumn prescribed burning, with many of these moister aspects potentially providing longer unburnt refuges over multiple burn rotations. The fire severity and extent mapping products, produced using the methodology outlined in this study, have the potential to substantially increase the understanding of the ecological and fuel outcomes of landscape‐scale autumn prescribed burning.

Landslide Susceptibility Assessment Using Frequency Ratio Technique with Iterative Random Sampling

This paper assesses the performance of the landslide susceptibility analysis using frequency ratio (FR) with an iterative random sampling. A pair of before-and-after digital aerial photographs with 50 cm spatial resolution was used to detect landslide occurrences in Yongin area, Korea. Iterative random sampling was run ten times in total and each time it was applied to the training and validation datasets. Thirteen landslide causative factors were derived from the topographic, soil, forest, and geological maps. The FR scores were calculated from the causative factors and training occurrences repeatedly ten times. The ten landslide susceptibility maps were obtained from the integration of causative factors that assigned FR scores. The landslide susceptibility maps were validated by using each validation dataset. The FR method achieved susceptibility accuracies from 89.48% to 93.21%. And the landslide susceptibility accuracy of the FR method is higher than 89%. Moreover, the ten times iterative FR modeling may contribute to a better understanding of a regularized relationship between the causative factors and landslide susceptibility. This makes it possible to incorporate knowledge-driven considerations of the causative factors into the landslide susceptibility analysis and also be extensively used to other areas.

航摄与机载激光雷达技术在河道地形测量中的应用

随着数字航空摄影及激光雷达技术的发展，这种非接触式测量技术成本低、快速高效、机动灵活的优势也越来越显著。结合长江干流1:10,000河道地形测量项目，介绍了航空摄影及激光雷达技术相结合的作业方式及其在大面积的洲滩、植被高覆盖河道地形测量中的应用情况，并对成图精度进行了检测分析，结果表明成果精度满足相关规范要求，这种联合作业模式应用于河道地形测绘中是可行的。 With the development of digital aerial photography and lidar technology, because of its low cost, high efficiency and flexible, this non-contact measurement technology is becoming more and more significant. Based on the 1:10,000 riverway topographic survey project of Yangtze River, we introduced the operation mode of aerial photography and lidar technology and the application of riverway topographic survey in a large bottomland and high vegetation coverage area, and statistically analyzed the accuracy of topographic map. The results show that the surveying precision satisfies the requirements of relevant specifications, and this combined operating mode used in riverway topographic Survey is feasible.

Comparison of Pixel-based and Object-based Methods of Land Cover Classification of Urban AreasUsing High-resolution Digital Aerial Photography

Comparison of Pixel-based and Object-based Methods of Land Cover Classification of Urban AreasUsing High-resolution Digital Aerial Photography

Assessment of Geographic Information System (GIS) Skills Employed by Graduates from Three Forestry Programs in the United States

This research evaluates the current use of geographic information systems (GIS) by forestry program graduates employed in the United States who graduated from university in the past five years. The purpose was to understand what geospatial processes and databases are typically used by field foresters. A survey was designed and sent to recent forestry graduates from Mississippi State University, Oregon State University, and the University of Georgia, with 30% of those surveyed choosing to participate. The majority of forestry graduates surveyed use GIS at least once a week, and the most frequently employed tasks included editing tabular data, adjusting polygon boundaries, buffering and splitting polygons, and querying for spatial and tabular information. Very few overlay or advance spatial analysis tools were noted as used in regular work efforts. Most respondents use digital aerial photographs as reference, along with satellite images. LiDAR is increasingly being used by these foresters, but to a lesser extent. ArcMap and Google Earth were noted as the most commonly used software packages. Most foresters rely on an organization’s technical support staff for assistance. The study results can be used as a guide for academic programs in their efforts to provide timely and effective knowledge on geospatial topics to forestry undergraduate students.

디지털 항공사진 판독기법을 이용한 산사태 발생 위험지 예측에 관한 연구: 우면산 일대를 대상으로

디지털 항공사진 판독기법을 이용한 산사태 발생 위험지 예측에 관한 연구: 우면산 일대를 대상으로

Late Wisconsinan deglaciation and proglacial lakes development in the Charlevoix region, southeastern Québec, Canada

The Charlevoix region, in southeastern Quebec, is characterized by a dramatic landscape formed by the junction of the Laurentian Highlands, the Charlevoix Astrobleme and the St Lawrence Estuary. At the Last Glacial Maximum (LGM), the region was completely covered by the Laurentide Ice Sheet (LIS). The complex topography of the region was the stage of many of the major deglacial events of southern Quebec (e.g. Goldthwait Sea Invasion, St Lawrence Ice-Stream, Saint-Narcisse Episode). We present a detailed reconstruction of the pattern of retreat of the LIS in the Charlevoix region based on the interpretation of ice-marginal features (e.g. moraines, fans) and glaciolacustrine landforms and deposits, two extensive field campaigns, and the interpretation of high-resolution 3D digital aerial photographs and LiDAR data. Our results indicate five moraine complexes in the region: the Rochette, the Brulee, the Sainte-Anne, the Saint-Narcisse and the Mars-Batiscan complexes. Deltas, fans, fine-grained sediments, littoral deposits, drainage breaches and deposits were used to identify 91 palaeo-proglacial lakes. The identification of these lakes and their relation to moraine complexes enabled the reconstruction of six stages of lake development during the Charlevoix deglaciation. The development of proglacial lakes occurred in all types of terrain (highlands, lowlands, transitory levels above marine limit). We conclude that local topography had a decisive effect on promoting both moraine deposition and lake development. We suggest that similar topographical regions (hilly-mountainous) that were affected by major ice-margin stabilizations during glacial retreat should have experience small lakes dominating valleys and topographical lows.

Obtaining biophysical measurements of woody vegetation from high resolution digital aerial photography in tropical and arid environments: Northern Territory, Australia

Biophysical parameters obtained from woody vegetation are commonly measured using field based techniques which require significant investment in resources. Quantitative measurements of woody vegetation provide important information for ecological studies investigating landscape change. The fine spatial resolution of aerial photography enables identification of features such as trees and shrubs. Improvements in spatial and spectral resolution of digital aerial photographic sensors have increased the possibility of using these data in quantitative remote sensing. Obtaining biophysical measurements from aerial photography has the potential to enable it to be used as a surrogate for the collection of field data. In this study quantitative measurements obtained from digital aerial photography captured at ground sampling distance (GSD) of 15cm (n=50) and 30cm (n=52) were compared to woody biophysical parameters measured from 1ha field plots. Supervised classification of the aerial photography using object based image analysis was used to quantify woody and non-woody vegetation components in the imagery. There was a high correlation (r≥0.92) between all field measured woody canopy parameters and aerial derived green woody cover measurements, however only foliage projective cover (FPC) was found to be statistically significant (paired t-test; α=0.01). There was no significant difference between measurements derived from imagery captured at either GSD of 15cm and 30cm over the same field site (n=20). Live stand basal area (SBA) (m2ha−1) was predicted from the aerial photographs by applying an allometric equation developed between field-measured live SBA and woody FPC. The results show that there was very little difference between live SBA predicted from FPC measured in the field or from aerial photography. The results of this study show that accurate woody biophysical parameters can be obtained from aerial photography from a range of woody vegetation communities across the Northern Territory.

NATIONWIDE HYBRID CHANGE DETECTION OF BUILDINGS

Abstract. The Fundamental Base of Geographic Data of the Czech Republic (hereinafter FBGD) is a national 2D geodatabase at a 1:10,000 scale with more than 100 geographic objects. This paper describes the design of the permanent updating mechanism of buildings in FBGD. The proposed procedure belongs to the category of hybrid change detection (HCD) techniques which combine pixel-based and object-based evaluation. The main sources of information for HCD are cadastral information and bi-temporal vertical digital aerial photographs. These photographs have great information potential because they contain multispectral, position and also elevation information. Elevation information represents a digital surface model (DSM) which can be obtained using the image matching technique. Pixel-based evaluation of bi-temporal DSMs enables fast localization of places with potential building changes. These coarse results are subsequently classified through the object-based image analysis (OBIA) using spectral, textural and contextual features and GIS tools. The advantage of the two-stage evaluation is the pre-selection of locations where image segmentation (a computationally demanding part of OBIA) is performed. It is not necessary to apply image segmentation to the entire scene, but only to the surroundings of detected changes, which contributes to significantly faster processing and lower hardware requirements. The created technology is based on open-source software solutions that allow easy portability on multiple computers and parallelization of processing. This leads to significant savings of financial resources which can be expended on the further development of FBGD.