Polygon Data Research Articles

Disaggregation of legacy soil data using area to point kriging for mapping soil organic carbon at the regional scale

Legacy data in the form of soil maps, which often have typical property measurements associated with each polygon, can be an important source of information for digital soil mapping (DSM). Methods of disaggregating such information and using it for quantitative estimation of soil properties by methods such as regression kriging (RK) are needed. Several disaggregation processes have been investigated; preferred methods include those which include consideration of scorpan factors and those which are mass preserving (pycnophylactic) making transitions between different scales of investigation more theoretically sound. Area to point kriging (AtoP kriging) is pycnophylactic and here we investigate its merits for disaggregating legacy data from soil polygon maps. Area to point regression kriging (AtoP RK) which incorporates ancillary data into the disaggregation process was also applied. The AtoP kriging and AtoP RK approaches do not involve collection of new soil measurements and are compared with disaggregation by simple rasterization. Of the disaggregation methods investigated, AtoP RK gave the most accurate predictions of soil organic carbon (SOC) concentrations (smaller mean absolute errors (MAEs) of cross-validation) for disaggregation of soil polygon data across the whole of Northern Ireland.Legacy soil polygon data disaggregated by AtoP kriging and simple rasterization were used in a RK framework for estimating soil organic carbon (SOC) concentrations across the whole of Northern Ireland, using soil sample data from the Tellus survey of Northern Ireland and with other covariates (altitude and airborne radiometric potassium). This allowed direct comparison with previous analysis of the Tellus survey data. Incorporating the legacy data, whether from simple rasterization of the polygons or AtoP kriging, substantially reduced the MAEs of RK compared with previous analyses of the Tellus data. However, using legacy data disaggregated by AtoP kriging in RK resulted in a greater reduction in MAEs. A jack-knife procedure was also performed to determine a suitable number of additional soil samples that would need to be collected for RK of SOC for the whole of Northern Ireland depending on the availability of ancillary data. We recommend i) if only legacy soil polygon map data are available, they should be disaggregated using AtoP kriging, ii) if ancillary data are also available legacy data should be disaggregated using AtoP RK and iii) if new soil measurements are available in addition to ancillary and legacy soil map data, the legacy soil map data should be first disaggregated using AtoP kriging and these data used along with ancillary data as the fixed effects for RK of the new soil measurements.

Preliminary Study Evaluating the Accuracy of MRI Images on CBCT Images in the Field of Orthodontics

The purpose of this study was to explore the 3-dimensional (3D) accuracy of magnetic resonance imaging (MRI) on cone-beam computed tomography (CBCT) images after the registration of MRI images on CBCT images. Three Japanese adult females volunteered for this study. To transform digital imaging and communication in medicine (DICOM) data derived from MRI and CBCT images into polygon data, five software programs were used. CBCT and MRI images were obtained within one week, and both were registered by the iterative closest point (ICP) method. To assess the accuracy of the composite MRI-CBCT, the measurement errors of the MRI-CBCT were verified Measurement values were compared using frontal and cephalometric soft-tissue landmarks. Differences were analyzed using the non-parametric Mann-Whitney U test. There were no significant linear measurement errors (P > 0.05) when the images were measured from the superimposed MRI-CBCT images. The MRI images attained from MRI - CBCT registration showed accurate 3D linear measurements.

Generating seamless surfaces for transport and dispersion modeling in GIS

A standard use of triangulation in GIS is to model terrain surface using TIN. In many simulation models of physical phenomena, triangulation is often used to depict the entire spatial domain, which may include buildings, landmarks and other surface objects in addition to the terrain surface. Creating a seamless surface of complex building structures together with the terrain is challenging and existing approaches are laborious, time-consuming and error-prone. We propose an efficient and robust procedure using computational geometry techniques to derive triangulated building surfaces from 2D polygon data with a height attribute. We also propose a new method to merge the resultant building surfaces with the triangulated terrain surface to produce a seamless surface for the entire study area. Using Oklahoma City data, we demonstrate the proposed method. The resultant surface is used as the input data for a simulated transport and dispersion event in Oklahoma City. The proposed method can produce the seamless surface data to be used for various types of physical models in a fraction of the time required by previous methods.

Displacement patches for view-dependent rendering

In this paper we present a new approach for interactive view-dependent rendering of large polygonal data sets which relies on advanced features of modern graphics hardware. Our preprocessing algorithm starts by generating a simplified representation of the input mesh. It then builds a multiresolution hierarchy for the simplified model. For each face in the hierarchy, it generates and assigns a displacement map that resembles the original surface represented by that face. At runtime, the multiresolution hierarchy is used to select a coarse view-dependent level-of-detail representation, which is sent to the graphics hardware. The GPU then refines the coarse representation by replacing each face with a planar tile, which is elevated according to the assigned displacement map. Our results show that our implementation achieves quality images at high frame rates.

Effects of soil spatial resolution on quantifying CH4and N2O emissions from rice fields in the Tai Lake region of China by DNDC model

[1] Fourteen grid data sets of different cell resolutions were generated, from 0.5 × 0.5 km to 64 × 64 km, to estimate CH4 and N2O emissions from paddy soils in the Tai Lake region of China using the Denitrification-Decomposition (DNDC) model. The grids were derived from a polygon-based data set (1:50,000 digital soil map/database), which was the most detailed soil database for the region. Comparison of simulated CH4 and N2O concentrations from input of the 14 grid data sets with the original polygon data demonstrated (1) no distinct variability (relative errors 10%) in the results when grid data sets with cell size of >8 km were applied as input. A grid data set with a cell size of 8 km was found to be optimal based on accuracy and computational efficiency of DNDC simulations. The results can be used as a guideline for optimizing field sampling strategies for locations where there is a lack of or insufficient soil data, whereby soil data can be collected through sampling in cell centers of designed grid frames.

MCGIM-based model streaming for realtime progressive rendering

While most mesh streaming techniques focus on optimizing the transmission order of the polygon data, few approaches have addressed the streaming problems by using geometry images (GIM). In this paper, we present a new approach which firstly partitions a mesh into several surface patches, then converts these patches into multi-chart geometry images (MCGIM). After resampling the MCGIM and normal map atlas are obtained, we hierarchically construct the regular geometry image representation by adopting the quadtree structure. In this way, the encoded nodes can be transmitted in arbitrary order with high transmission flexibility. Also, the rendering quality of the partially transmitted models can be greatly improved by using the normal texture atlas. Meanwhile only the geometry on the silhouette to the current viewpoint are required to be refined and transmitted, therefore the amount of data is minimized for transferring each frame. In particular, our approach also allows users to encode and transmit the mesh data via JPEG2000 technique. Therefore, our mesh streaming method is suitable for transmitting 3D animation models with use of Motion JPEG2000 videos. Experimental results have demonstrated the effectiveness of our approach, which enables one server to stream the MCGIM texture atlas to the clients. Also, the transmitted model can be rendered in a multiresolution manner by GPU acceleration on the client side, due to the regular geometry structure of MCGIM.

Some Results of 3D Terrain Splitting by2D Polygonal Vector Data

Some Results of 3D Terrain Splitting by2D Polygonal Vector Data

Computer-generated image hologram

We investigate the computer-generated hologram with full parallax and which can be reconstructed with white light. The object of the hologram is processed from three-dimensional computer graphics polygon data and has shaded surface for hidden surface removal. The optically reconstructed image from the printed hologram is evaluated.

Multivariate Areal Interpolation for Continuous and Count Data

Geographic information system (GIS) users often need to disaggregate and reaggregate data collected in polygons, but classical kriging models only allow for data collected in points. We discuss our implementation of areal interpolation, a kriging-based disaggregation technique, in the Geostatistical Analyst extension of ArcGIS 10.1 for Gaussian, binomial, and overdispersed Poisson data. All methods allow for surfaces of prediction standard errors. We also allow for the use of a secondary cokriging variable, which can be any of the three above-mentioned distributions. Our areal interpolation model overcomes several computational problems, such as how to handle polygons of vastly different sizes and how to analyze polygons that are overlapping or disjoint.For Gaussian data averaged over polygons, the output is a surface predicting the value at each individual location. Gaussian polygonal data may arise when continuous point measurements are averaged to polygons in order to protect privacy or reduce overhead, and the original point data is discarded. For polygons containing Poisson counts, the output is a surface predicting the density of counts at each location in the data domain. Our model allows for overdispersed counts and for different observation times between polygons. The output for binomial data is a surface predicting the underlying risk at each location of seeing an individual with a certain trait. Each polygon of the input data must contain a count and a population value. The latter indicates the number of individuals sampled, and the former indicates the number of sampled individuals with a certain trait.Once a prediction surface has been created, predictions can be aggregated back to a new set of polygons. This allows for the collection of data over one set of polygons and the prediction for a different set of polygons. We discuss diagnostic options for determining how well the data fits a model, and we demonstrate areal interpolation with three case studies.

Collection, Analysis, and Distribution of Three-Dimensional CT Data from Primate and Other Skull Specimens

We propose a method for obtaining three-dimensional digitized morphology using skull collections from natural history museums. The skull specimens are three-dimensionally digitized by computed tomography (CT), and the original morphological data is stored on a hard disk or server in the natural history museum. The data can be used to morphologically observe and describe the skulls in detail. The skulls can be examined freely from any viewing angle and can be partially removed for nondestructive observations of the inner structure of the specimens. It is possible to quantitatively analyze the form and function of the skulls by using the three-dimensional coordinates. For example the visual system can be functional-morphologically examined in each species by using the three-dimensional coordinates structurally related to orbits or optic nerves. The data were installed as DICOM-standard formatted files, and could be converted to polygonal data using available software. The three-dimensional data can be used in the following manners: (1) volume rendering from voxel data of DICOM-formatted files for qualitative observations of the specimens, and (2) conversion of the DICOM-formatted files to polygonal data for fine osteometry, computer graphics, and artistic design. The DICOM-formatted data can be accessed freely via the internet by users worldwide.

Exploration of a polygon decomposition technique based on the ordinary Voronoi diagram

Voronoi diagrams have been integral to the efforts aimed at reducing the difficulty of representing and modeling spatial phenomena. This article extends a polygon decomposition procedure based on ordinary Voronoi diagrams (OVDs) that can produce substitute representations for contiguous polygon objects in spatial analytic situations. It is based on a relatively unexplored conceptual linkage between polygon objects in a vector environment and their ordinary Voronoi-based counterparts. It facilitates the ability to represent typical polygon data with OVDs by exploiting the regularity inherent to the spatial configuration of the polygons in data structures. A discussion is provided for complexity issues and other theoretical concerns associated with using the decomposition procedure. A series of examples to explore the accuracy of the Voronoi-based representations is presented, including one using them in a geographic information system (GIS)-based spatial analysis of the bus transit coverage problem. Results suggest that the Voronoi approach may successfully reproduce polygon data in certain analytical situations and reduce the complexity of spatial operations when using large datasets. A time complexity analysis with sample data is also performed, which demonstrates computational savings attributable to the approach. Given this experience with the technique, several possibilities for future research are laid out.

Applying systematic conservation planning principles to palustrine and inland saline wetlands of New Zealand

Summary1. Previous attempts to identify nationally important wetlands for biodiversity in New Zealand were based on expert panel opinions because quantitative approaches were hampered by a lack of data. We apply principles of systematic conservation planning to remote sensing data within a geographical information system (GIS) to identify nationally important palustrine and inland saline wetlands.2. A catchment‐based classification was used to divide New Zealand into 29 biogeographic units. To meet representation goals, all wetland classes need to be protected within each unit.3. We mapped current and historic wetlands down to a minimum size of 0.5 ha. Over 7000 current wetlands were mapped using standardised satellite imagery and a collection of point or polygon data. Historical extent was estimated from soil information refined using a digital elevation model. The current extent of wetlands is 10% of the historic extent, which is consistent with previous estimates.4. A classification was produced using fuzzy expert rules within a GIS to identify seven wetland classes: bog, fen, swamp, marsh, pakihi/gumland, seepage and inland saline. Swamps and pakihi/gumland are the most common, but the former has sustained the greatest reduction in area with only 6% of its historical extent remaining. A preliminary field assessment of classification accuracy in the Otago region found only 60% agreement, mainly because of the misclassification of marshes into swamps.5. Wetland condition was estimated using six measures of human disturbance (natural cover, human‐made impervious cover, introduced fish, woody weeds, artificial drainage and nitrate leaching risk) applied at three spatial scales: the wetland’s catchment, a 30‐m buffer around the wetland and the wetland itself. Measures were transformed and combined into a single condition index. More than 60% of remaining wetlands had condition indices <0.5, probably indicating moderate to severe degradation and loss of native biodiversity.6. Sites were ranked within each biogeographic unit using the wetland classification to ensure a representative set of wetland diversity. Rankings were determined by combining condition and complementarity to calculate conservation effectiveness that was then weighted by irreplaceability. Highest ranked sites in each biogeographic unit were usually the largest remaining wetlands that contained multiple wetland classes. This reflects their potential to protect a diverse range of wetland classes and a high proportion of the remaining habitat.

Using Superimposition of 3-Dimensional Cone-Beam Computed Tomography Images with Surface-Based Registration in Growing Patients

The purpose of this research was to evaluate a new method of superimposing detailed cone-beam computed tomography (CBCT) images. This study used 5 different software programs to transform the digital imaging and communication in medicine (DICOM) data from CBCT image into polygon data. The data conversion errors from different software programs were verified by the poly-acetal ball test and the dry skull test. The iterative closest point (ICP) method was used for precise superimposition. To evaluate changes related to growth, three different domains were superimposed in order to investigate appropriate areas for evaluation by the ICP method. The ICP method in the cranial base (excluding the peripheral zone) was indicated as the most reliable surface in this research. There were no measurement errors in converting the image data between software programs. The ICP method in the cranial base (excluding the peripheral zone) is one of the most accurate methods for superimposition when the mandibular rotation or displacement has not occurred during growth or treatment. This 3-dimensional (3D) superimposition technique can be used for a valid and reproducible assessment of treatment outcomes for growing subjects. This method is considered to be of clinical value because of the manageability and 3D accuracy of the data comparison with multi planar reconstruction (MPR) images.

Error term in pointwise approximation of the curvature of a curve

Let P be a polygonal line approximating a planar curve Γ, the discrete curvature k d ( P ) at a vertex P ∈ P is (usually) defined to be the quotient of the angle between the normals of the two segments with vertex P by the average length of these segments. In this article we give an explicit upper bound of the difference | k ( P ) − k d ( P ) | between the curvature k ( P ) at P of the curve and the discrete curvature in terms of the polygonal line's data, the supremums over Γ of the curvature function k and its derivative k ′ , and a new geometrical invariant, the return factor Ω Γ . One consequence of this upper bound is that it is not needed to know precisely which curve is passing through the vertices of the polygonal line P to have a pointwise information on its curvature.

Computation of a tetrahedral mesh for striated muscle deformation simulation

Competing concepts exist regarding surgery for instance of the cleft lip and palate to date. Morphology-based simulations at histological scale may one day be used to help the surgeon predict the possible outcome of a variety of approaches. It however can be a challenge to generate volume meshes that are applicable to the mathematical modelling of three-dimensional spatial modifications. Computation of surface meshes may be considered less delicate. The aim of this study is to design and evaluate a novel algorithm that supports finite element methods. Images of histological serial sections of a striated muscle were segmented. Results of the three-dimensional reconstruction of multiple layers of the polygonal segmentation data characterized the hull of the muscle. The corresponding surface mesh was then converted into a tetrahedral mesh to generate volume. This was achieved by mapping multiple template types onto neighbouring intersection polygons. Muscle contraction was subsequently simulated by mesh deformation. The technique successfully generated volumes and was able to provide data on contraction directions. The mesh supported a novel approach to simulate representations of contraction. However, several drawbacks were evident. Mathematical modelling of scenarios with more than one striated muscle will require considerable modification of the currently presented approach. Future studies need to then evaluate the applicability of volume meshes to represent arrays of three-dimensional biological objects. Surface mesh based mathematical modelling of cleft lip and palate surgery and its results are therefore not yet in reach.

An interactive visualization tool for multi-channel confocal microscopy data in neurobiology research

Confocal microscopy is widely used in neurobiology for studying the three-dimensional structure of the nervous system. Confocal image data are often multi-channel, with each channel resulting from a different fluorescent dye or fluorescent protein; one channel may have dense data, while another has sparse; and there are often structures at several spatial scales: subneuronal domains, neurons, and large groups of neurons (brain regions). Even qualitative analysis can therefore require visualization using techniques and parameters fine-tuned to a particular dataset. Despite the plethora of volume rendering techniques that have been available for many years, the techniques standardly used in neurobiological research are somewhat rudimentary, such as looking at image slices or maximal intensity projections. Thus there is a real demand from neurobiologists, and biologists in general, for a flexible visualization tool that allows interactive visualization of multi-channel confocal data, with rapid fine-tuning of parameters to reveal the three-dimensional relationships of structures of interest. Together with neurobiologists, we have designed such a tool, choosing visualization methods to suit the characteristics of confocal data and a typical biologist's workflow. We use interactive volume rendering with intuitive settings for multidimensional transfer functions, multiple render modes and multi-views for multi-channel volume data, and embedding of polygon data into volume data for rendering and editing. As an example, we apply this tool to visualize confocal microscopy datasets of the developing zebrafish visual system.

Reconstruction of Kyoto of the Edo era based on arts and historical documents: 3D urban model based on historical GIS data

This paper explores a method for creating large-scale urban 3D models using Historical GIS data. The method is capable of automatically generating realistic VR models based on GIS data at a low cost. 3D models of houses are created from polygon data, fences from line data, and pedestrians and trees from point data. The method is applied to the Virtual Kyoto Project in which the landscape of the whole city of Kyoto of the early Edo era (ca 17C) is reconstructed.

Extreme Coefficients in Geographically Weighted Regression and Their Effects on Mapping

This study deals with the issue of extreme coefficients in geographically weighted regression (GWR) and their effects on mapping coefficients using three datasets with different spatial resolutions. We found that although GWR yields extreme coefficients regardless of the resolution of the dataset or types of kernel function: (1) GWR tends to generate extreme coefficients for less spatially dense datasets; (2) coefficient maps based on polygon data representing aggregated areal units are more sensitive to extreme coefficients; and (3) coefficient maps using bandwidths generated by a fixed calibration procedure are more vulnerable to the extreme coefficients than adaptive calibration.

Combined object-based classification and manual interpretation–synergies for a quantitative assessment of parcels and biotopes

Recent technical advances in remote sensing data capture and spatial resolution lead to a widening gap between increasing data availability on the one hand and insufficient methodology for semi-automated image data processing and interpretation on the other hand. At the interface of GIS and remote sensing, object-based image analysis methodologies are one possible approach to close this gap. With this, methods from either side are integrated to use both the capabilities of information extraction from image data and the power to perform spatial analysis on derived polygon data. However, dealing with image objects from various sources and in different scales implies combining data with inconsistent boundaries. A landscape interpretation support tool (LIST) is introduced which seeks to investigate and quantify spatial relationships among image objects stemming from different sources by using the concept of spatial coincidence. Moreover, considering different categories of object fate, LIST enables a change categorization for each polygon of a time series of classifications. The application of LIST is illustrated by two case-studies, using Landsat TM and ETM as well as CIR aerial photographs: the first showing how the tool is used to perform object quantification and change analysis; the latter demonstrating how superior aggregation capabilities of the human brain can be combined with the fine spatial segmentation and classification. Possible fields of application are identified and limitations of the approach are discussed.

Development of highly accurate global polygonal drainage basin data

AbstractHighly accurate global polygonal drainage basin data (PDBD) was developed in this research. The PDBD was derived from digital elevation models (DEMs) at high‐resolution (about 100 m–1 km) by automatic and non‐automatic methods to suppress DEM errors which derive wrong PDBD. The automatic methods are ‘stream burning’ and ‘ridge fencing’, while the non‐automatic method is one which manually corrects DEM errors (‘manual correction’). For the derivation of the PDBD, we collected and used geographic basin and river data published from governments, institutes, publishers, and water‐related programs. The PDBD derived from the DEMs at high‐resolution can represent the boundaries of the basins in detail, and precise geographic and topographic information can be thus derived. These features are helpful for regional and global analysis, assessment, and management with hydrological models in water‐related studies. To assess the accuracy of the derived PDBD, we conducted two types of comparisons. Firstly, we geographically compared the derived PDBD with the collected basin data. The derived PDBD showed good geographic agreement with the collected basin data, and the geographic agreement of the derived PDBD was better than that of HYDRO1k. Secondly, we compared upstream areas and discharges based on the derived PDBD with the observed upstream areas and discharges. The upstream areas and discharges based on the derived PDBD showed good agreement with the observed upstream areas and discharges, and the agreement of the derived PDBD was better than that of HYDRO1k. These comparisons reveal that the derived PDBD are highly accurate and reliable. The derived PDBD are thus thought to offer the best information on the surface drainage of the earth. Copyright © 2008 John Wiley & Sons, Ltd.