LIVIVO - The Search Portal for Life Sciences

zur deutschen Oberfläche wechseln
Advanced search

Search results

Result 1 - 10 of total 12

Search options

  1. Article ; Online: Global and local magnitude and spatial pattern of uncertainty from geographically adaptive empirical and machine learning satellite-derived bathymetry models

    Kim Lowell / Yuri Rzhanov

    GIScience & Remote Sensing, Vol 61, Iss

    2024  Volume 1

    Abstract: ABSTRACTThe spatial structure of local uncertainty of shallow-water satellite-derived bathymetry (SDB) relative to model type, imagery, and geographical adaptability was examined for an area near Key West, Florida (United States). The model types ... ...

    Abstract ABSTRACTThe spatial structure of local uncertainty of shallow-water satellite-derived bathymetry (SDB) relative to model type, imagery, and geographical adaptability was examined for an area near Key West, Florida (United States). The model types examined were a commonly used quasi-empirical linear regression model and a decision tree-based Categorical Boosting (CatBoost) machine learning (ML) model. Image types examined were (four) cloud-free Sentinel-2 images and a maximum blue band (Band 2) value image composite of the four Sentinel-2 images. Initial models fitted were based on band reflectances alone. Geographical adaptivity was added by including UTM coordinates and refitting the models. Major findings were: 1) The ML/CatBoost models provided substantially better depth estimates than the quasi-empirical models. 2) The geographically adaptive models outperformed the non-geographically adaptive models. 3) The ML/CatBoost models that included non-visible spectral bands including infra-red improved SDB accuracy compared to ML/CatBoost and quasi-empirical models based only on visible spectral bands. 4) Accuracies from ML/CatBoost models were comparable across all individual images and the composite suggesting that CatBoost models eliminate or at least minimize the need to find “the best” cloud-free image nor is it necessary to create a composite image. 5) Localized SDB inaccuracy was spatially random. 6) Significant spatial hotspots where SDB accuracy was consistently higher or lower across all images and models were present. Results suggest that image selection is less important for global and local SDB accuracy than using ML models that detect hidden interactions and non-linear relationships among pixel reflectance and geographic location. The spatially random local deviation from global accuracy suggests a weak ability to infer local accuracy from neighboring accuracies. This lack of spatial autocorrelation among errors is potentially problematic for the use of SDB maps for navigation since error at any ...
    Keywords Airborne LiDAR ; image composite ; categorical Boosting ; global moran’s i ; local moran’s i ; Mathematical geography. Cartography ; GA1-1776 ; Environmental sciences ; GE1-350
    Subject code 333
    Language English
    Publishing date 2024-12-01T00:00:00Z
    Publisher Taylor & Francis Group
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  2. Article ; Online: Assessing Marginal Shallow-Water Bathymetric Information Content of Lidar Sounding Attribute Data and Derived Seafloor Geomorphometry

    Kim Lowell / Brian Calder

    Remote Sensing, Vol 13, Iss 1604, p

    2021  Volume 1604

    Abstract: Shallow-water depth estimates from airborne lidar data might be improved by using sounding attribute data (SAD) and ocean geomorphometry derived from lidar soundings. Moreover, an accurate derivation of geomorphometry would be beneficial to other ... ...

    Abstract Shallow-water depth estimates from airborne lidar data might be improved by using sounding attribute data (SAD) and ocean geomorphometry derived from lidar soundings. Moreover, an accurate derivation of geomorphometry would be beneficial to other applications. The SAD examined here included routinely collected variables such as sounding intensity and fore/aft scan direction. Ocean-floor geomorphometry was described by slope, orientation, and pulse orthogonality that were derived from the depth estimates of bathymetry soundings using spatial extrapolation and interpolation. Four data case studies (CSs) located near Key West, Florida (United States) were the testbed for this study. To identify bathymetry soundings in lidar point clouds, extreme gradient boosting (XGB) models were fitted for all seven possible combinations of three variable suites—SAD, derived geomorphometry, and sounding depth. R 2 values for the best models were between 0.6 and 0.99, and global accuracy values were between 85% and 95%. Lidar depth alone had the strongest relationship to bathymetry for all but the shallowest CS, but the SAD provided demonstrable model improvements for all CSs. The derived geomorphometry variables contained little bathymetric information. Whereas the SAD showed promise for improving the extraction of bathymetry from lidar point clouds, the derived geomorphometry variables do not appear to describe geomorphometry well.
    Keywords lidar point attribute data ; spatial extrapolation ; extreme gradient boosting ; bathymetry ; Florida Keys ; Science ; Q
    Subject code 333
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  3. Article ; Online: Global-Local-Comparison Approach

    Hilary Kates Varghese / Kim Lowell / Jennifer Miksis-Olds

    Frontiers in Marine Science, Vol

    Understanding Marine Mammal Spatial Behavior by Applying Spatial Statistics and Hypothesis Testing to Passive Acoustic Data

    2021  Volume 8

    Abstract: Technological innovation in underwater acoustics has progressed research in marine mammal behavior by providing the ability to collect data on various marine mammal biological and behavioral attributes across time and space. But with this comes the need ... ...

    Abstract Technological innovation in underwater acoustics has progressed research in marine mammal behavior by providing the ability to collect data on various marine mammal biological and behavioral attributes across time and space. But with this comes the need for an approach to distill the large amounts of data collected. Though disparate general statistical and modeling approaches exist, here, a holistic quantitative approach specifically motivated by the need to analyze different aspects of marine mammal behavior within a Before-After Control-Impact framework using spatial observations is introduced: the Global-Local-Comparison (GLC) approach. This approach capitalizes on the use of data sets from large-scale, hydrophone arrays and combines established spatial autocorrelation statistics of (Global) Moran’s I and (Local) Getis-Ord Gi∗ (Gi∗) with (Comparison) statistical hypothesis testing to provide a detailed understanding of array-wide, local, and order-of-magnitude changes in spatial observations. This approach was demonstrated using beaked whale foraging behavior (using foraging-specific clicks as a proxy) during acoustic exposure events as an exemplar. The demonstration revealed that the Moran’s I analysis was effective at showing whether an array-wide change in behavior had occurred, i.e., clustered to random distribution, or vice-versa. The Gi∗ analysis identified where hot or cold spots of foraging activity occurred and how those spots varied spatially from one analysis period to the next. Since neither spatial statistic could be used to directly compare the magnitude of change between analysis periods, a statistical hypothesis test, using the Kruskal-Wallis test, was used to directly compare the number of foraging events among analysis periods. When all three components of the GLC approach were used together, a comprehensive assessment of group level spatial foraging activity was obtained. This spatial approach is demonstrated on marine mammal behavior, but it can be applied to a broad range of spatial ...
    Keywords spatial autocorrelation ; hypothesis testing ; Before-After Control-Impact ; marine mammal ; spatial change ; GLC approach ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
    Subject code 333
    Language English
    Publishing date 2021-10-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  4. Article ; Online: Spatial Analysis of Beaked Whale Foraging During Two 12 kHz Multibeam Echosounder Surveys

    Hilary Kates Varghese / Kim Lowell / Jennifer Miksis-Olds / Nancy DiMarzio / David Moretti / Larry Mayer

    Frontiers in Marine Science, Vol

    2021  Volume 8

    Abstract: To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in January of 2017 and ...

    Abstract To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in January of 2017 and 2019 off of San Clemente Island, California. The MBES surveys took place on the Southern California Antisubmarine Warfare Range (SOAR), which contains an array of 89 hydrophones covering an area of approximately 1800 km2 over which foraging beaked whales were detected. A spatial autocorrelation analysis of foraging effort was conducted using the Moran’s I (global) and the Getis-Ord Gi∗ (local) statistics, to understand the animals’ spatial use of the entire SOAR, as well as smaller areas, respectively, within the SOAR Before, During, and After the two MBES surveys. In both years, the global Moran’s I statistic suggested significant spatial clustering of foraging events on the SOAR during all analysis periods (Before, During, and After). In addition, a Kruskal-Wallis (comparison) test of both years revealed that the number of foraging events across analysis periods were similar within a given year. In 2017, the local Getis-Ord Gi∗ analysis identified hot spots of foraging activity in the same general area of the SOAR during all analysis periods. This local result, in combination with the global and comparison results of 2017, suggest there was no obvious period-related change detected in foraging effort associated with the 2017 MBES survey at the resolution measurable with the hydrophone array. In 2019, the foraging hot spot area shifted from the southernmost corner of the SOAR Before, to the center During, and was split between the two locations After the MBES survey. Due to the pattern of period-related spatial change identified in 2019, and the lack of change detected in 2017, it was unclear whether the change detected in 2019 was a result of MBES activity or some other environmental factor. Nonetheless, the results strongly suggest that the level of detected ...
    Keywords BACI ; multibeam echosounder ; beaked whale behavior ; spatial autocorrelation ; GLC approach ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
    Subject code 910 ; 333
    Language English
    Publishing date 2021-08-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  5. Article ; Online: Quantitative Soundscape Analysis to Understand Multidimensional Features

    Dylan Charles Wilford / Jennifer L. Miksis-Olds / S. Bruce Martin / Daniel R. Howard / Kim Lowell / Anthony P. Lyons / Michael James Smith

    Frontiers in Marine Science, Vol

    2021  Volume 8

    Abstract: A methodology for the analysis of soundscapes was developed in an attempt to facilitate efficient and accurate soundscape comparisons across time and space. The methodology consists of a collection of traditional soundscape metrics, statistical measures, ...

    Abstract A methodology for the analysis of soundscapes was developed in an attempt to facilitate efficient and accurate soundscape comparisons across time and space. The methodology consists of a collection of traditional soundscape metrics, statistical measures, and acoustic indices that were selected to quantify several salient properties of marine soundscapes: amplitude, impulsiveness, periodicity, and uniformity. The metrics were calculated over approximately 30 h of semi-continuous passive acoustic data gathered in seven unique acoustic environments. The resultant metric values were compared to a priori descriptions and cross-examined statistically to determine which combination most effectively captured the characteristics of the representative soundscapes. The best measures of amplitude, impulsiveness, periodicity, and uniformity were determined to be SPLrms and SPLpk for amplitude, kurtosis for impulsiveness, an autocorrelation based metric for periodicity, and the Dissimilarity index for uniformity. The metrics were combined to form the proposed “Soundscape Code,” which allows for rapid multidimensional and direct comparisons of salient soundscape properties across time and space. This initial characterization will aid in directing further analyses and guiding subsequent assessments to understand soundscape dynamics.
    Keywords soundscape ; kurtosis ; Dissimilarity Index ; ocean sound ; metrics ; marine acoustics ; Science ; Q ; General. Including nature conservation ; geographical distribution ; QH1-199.5
    Language English
    Publishing date 2021-08-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  6. Article: Ecosystem services from community-based forestry in Nepal: Realising local and global benefits

    Paudyal, Kiran / Himlal Baral / Kim Lowell / Rodney J. Keenan

    Land use policy. 2017 Apr., v. 63

    2017  

    Abstract: Community-based Forestry (CBF) is now a popular approach for landscape restoration, forest management, biodiversity conservation and support for rural livelihoods worldwide. The Himalayan country Nepal has been at the forefront of CBF for over four ... ...

    Abstract Community-based Forestry (CBF) is now a popular approach for landscape restoration, forest management, biodiversity conservation and support for rural livelihoods worldwide. The Himalayan country Nepal has been at the forefront of CBF for over four decades, with almost 40% of the total population directly involved in protecting and managing more than 32% of the country’s forested land. However, in the past, the focus of CBF in Nepal was the provision of goods for local subsistence, and there has been limited analysis of the role of CBF in providing ecosystem services (ES) from restored forest landscapes. Based on material drawn from a literature review and a stakeholders’ workshop, this paper analyses changes in Nepalese forest policies to provide a more holistic framework for CBF that provides a wider range of ES and to potentially underpin payments for ecosystem services in Nepal. The analysis indicates that Nepal’s forest policy and practices are still dominated by a narrowly conceived notion of forest management that does not accommodate the holistic concept of ES. The study illustrates that CBF provides many ES from local to global benefits as result of forest restoration. For example, timber, firewood, food, and water have local importance, while climate regulation, flood/erosion control, and habitat improvement have global importance. Many innovative cases are emerging in the long journey of CBF in Nepal that demonstrate more diverse management strategies, new forms of tenure rights and autonomy in institutional spaces. These can potentially provide a catalytic platform for the wider adoption of the ES framework in CBF regimes, in order to focus and reward forest management more directly for the provision of services such as water, biodiversity, climate regulation and recreation. Consequently, this study discusses the issues and challenges that are impeding the implementation of the ES concept in Nepal and suggests some ways forward.
    Keywords biodiversity ; climate ; community forestry ; ecosystem services ; erosion control ; forest management ; forest policy ; forest restoration ; forests ; fuelwood ; habitats ; landscape management ; landscapes ; livelihood ; recreation ; stakeholders ; Nepal
    Language English
    Dates of publication 2017-04
    Size p. 342-355.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 852476-2
    ISSN 0264-8377
    ISSN 0264-8377
    DOI 10.1016/j.landusepol.2017.01.046
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  7. Article ; Online: Detecting and Quantifying Forest Change

    Mihai A Tanase / Ismail Ismail / Kim Lowell / Oka Karyanto / Maurizio Santoro

    PLoS ONE, Vol 10, Iss 6, p e

    The Potential of Existing C- and X-Band Radar Datasets.

    2015  Volume 0131079

    Abstract: This paper evaluates the opportunity provided by global interferometric radar datasets for monitoring deforestation, degradation and forest regrowth in tropical and semi-arid environments. The paper describes an easy to implement method for detecting ... ...

    Abstract This paper evaluates the opportunity provided by global interferometric radar datasets for monitoring deforestation, degradation and forest regrowth in tropical and semi-arid environments. The paper describes an easy to implement method for detecting forest spatial changes and estimating their magnitude. The datasets were acquired within space-borne high spatial resolutions radar missions at near-global scales thus being significant for monitoring systems developed under the United Framework Convention on Climate Change (UNFCCC). The approach presented in this paper was tested in two areas located in Indonesia and Australia. Forest change estimation was based on differences between a reference dataset acquired in February 2000 by the Shuttle Radar Topography Mission (SRTM) and TanDEM-X mission (TDM) datasets acquired in 2011 and 2013. The synergy between SRTM and TDM datasets allowed not only identifying changes in forest extent but also estimating their magnitude with respect to the reference through variations in forest height.
    Keywords Medicine ; R ; Science ; Q
    Subject code 333 ; 910
    Language English
    Publishing date 2015-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  8. Article ; Online: Extension Activity Support System (EASY)

    Christopher Pettit / Eloise Seymour / Ian Miller / Lindsay Smith / Kim Lowell

    Future Internet, Vol 4, Iss 1, Pp 42-

    A Web-Based Prototype for Facilitating Farm Management

    2012  Volume 64

    Abstract: In response to disparate advances in delivering spatial information to support agricultural extension activities, the Extension Activity Support System (EASY) project was established to develop a vision statement and conceptual design for such a system ... ...

    Abstract In response to disparate advances in delivering spatial information to support agricultural extension activities, the Extension Activity Support System (EASY) project was established to develop a vision statement and conceptual design for such a system based on a national needs assessment. Personnel from across Australia were consulted and a review of existing farm information/management software undertaken to ensure that any system that is eventually produced from the EASY vision will build on the strengths of existing efforts. This paper reports on the collaborative consultative process undertaken to create the EASY vision as well as the conceptual technical design and business models that could support a fully functional spatially enabled online system.
    Keywords spatial information ; agriculture ; farm management ; web-based data delivery ; Information technology ; T58.5-58.64
    Language English
    Publishing date 2012-01-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    More links

    Kategorien

  9. Article: SAR and optical remote sensing: Assessment of complementarity and interoperability in the context of a large-scale operational forest monitoring system

    Lehmann, Eric A / Alex Held / Anthea Mitchell / Ian Tapley / Kim Lowell / Peter Caccetta / Tony Milne / Zheng-Shu Zhou

    Remote sensing of environment. 2015 Jan., v. 156

    2015  

    Abstract: In light of the growing volumes of remote sensing data generated by multiple space-borne platforms, integrated multi-sensor frameworks will continue to generate a significant interest in the frame of international forest monitoring initiatives. This work ...

    Abstract In light of the growing volumes of remote sensing data generated by multiple space-borne platforms, integrated multi-sensor frameworks will continue to generate a significant interest in the frame of international forest monitoring initiatives. This work investigates the interoperability of synthetic aperture radar (SAR) and optical datasets for the purpose of large-scale and operational forest monitoring. Using a discriminant technique known as canonical variate analysis, we investigate the level of discrimination (between forest and non-forest training sites) achieved by different datasets, thereby providing an assessment of complementarity between Landsat data and SAR data acquired at C-band (RADARSAT-2) and L-band (ALOS PALSAR), as well as related texture measures. Spatio-temporal methods developed as part of Australia's Land Cover Change Program (an established forest mapping and carbon accounting scheme operating at continental scale) are subsequently used for the integration of Landsat and (segmented) PALSAR data. To highlight specific operational aspects of the multi-sensor framework, this approach is demonstrated over the Australian state of Tasmania (approximately 6.8millionha), one of several national demonstrator sites defined by the Forest Carbon Tracking task of the Group on Earth Observations (GEO-FCT). In terms of complementarity, the combination of Landsat and L-band SAR data is found to provide most of the forest discrimination, while texture information and single-date C-band SAR data are found to provide only limited additional discrimination improvement in the frame of the considered monitoring system. The interoperability of optical and SAR data is assessed by comparison of forest maps resulting from the spatio-temporal processing under different scenarios, including: i) Landsat-only time series, ii) PALSAR-only time series, and iii) mixed Landsat–PALSAR time series. A comparison of the single-date optical and SAR-based forest classifications indicates a good agreement over Tasmania, with some bias towards forest in the PALSAR classifications. Significant differences are evident when considering the case of forest conversion (deforestation and afforestation) over large areas, thereby compromising the full interoperability of SAR and optical data within the framework of Australia's carbon accounting system.
    Keywords afforestation ; carbon ; data collection ; deforestation ; forests ; land cover ; Landsat ; monitoring ; remote sensing ; spatial data ; synthetic aperture radar ; texture ; time series analysis ; Tasmania
    Language English
    Dates of publication 2015-01
    Size p. 335-348.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 431483-9
    ISSN 0034-4257
    ISSN 0034-4257
    DOI 10.1016/j.rse.2014.09.034
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

  10. Article: Estimation of soil surface roughness of agricultural soils using airborne LiDAR

    Turner, Russell / Jeffrey P. Walker / Jorg M. Hacker / Kim Lowell / Mihai A. Tanase / Rocco Panciera

    Remote sensing of environment. 2014 Jan., v. 140

    2014  

    Abstract: Soil Surface Roughness (SR) provides a representation of surface variability which can be an important factor in a range of modelling applications such as surface water flow and sediment/nutrient transport. Moreover, it is a crucial parameter for ... ...

    Abstract Soil Surface Roughness (SR) provides a representation of surface variability which can be an important factor in a range of modelling applications such as surface water flow and sediment/nutrient transport. Moreover, it is a crucial parameter for interpreting backscatter characteristics of Synthetic Aperture Radar (SAR) for agricultural application such as near-surface soil moisture retrieval. SR is typically estimated using manual profiles of height variation along short transects (1 to 3m). However, this approach can be very time consuming and often only a small number of transects can be measured in this way, which may not be adequate to characterize the spatial variability of SR across the landscape. This study investigated the feasibility of utilising airborne Light Detection and Ranging (LiDAR) observations as an alternative for mapping SR attributes across an agricultural environment in New South Wales, Australia. To that end, SR attributes were extracted from airborne LiDAR observations and compared with those extracted from an extensive ground survey of SR making use of manual pin-profilers. Results show that LiDAR-estimates of soil profile surface heights Root Mean Square (RMS) are both accurate (compared to manual profiles) and precise (repeatable stable estimates) for fields presenting bare or fallow conditions and either presenting no row structure or as long as the orientation of the LiDAR scan line is perpendicular to the row structure. In such cases results indicated a strong correlation between LiDAR-estimated and ground-measured RMS estimates (R2>0.68, p<0.05), with an RMSE better than 0.81cm and bias smaller than 0.48cm from a 400m flight altitude. Moreover, estimates produced from repeat pass LiDAR datasets were consistent and highly correlated (R2 0.98) suggesting that the approach is precise and robust, provided that key tillage parameters (i.e. presence of vegetative material and row direction) can be pre-classified. LiDAR estimates of surface height RMS were shown to be accurate enough to allow the tracking of temporal changes in surface roughness due to farming activities. In contrast, LiDAR-derived surface Correlation Length (CL) estimates were not found to be a reliable proxy of the ground-measured CL.
    Keywords agricultural soils ; altitude ; data collection ; farming systems ; flight ; landscapes ; lidar ; models ; nutrient transport ; remote sensing ; sediments ; soil profiles ; soil water ; surface roughness ; surface water ; surveys ; synthetic aperture radar ; temporal variation ; tillage ; water flow ; New South Wales
    Language English
    Dates of publication 2014-01
    Size p. 107-117.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 431483-9
    ISSN 0034-4257
    ISSN 0034-4257
    DOI 10.1016/j.rse.2013.08.030
    Database NAL-Catalogue (AGRICOLA)

    More links

    Kategorien

To top