Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

A GEOMETRIC ACTIVE CONTOUR MODEL FOR HIGHWAY EXTRACTION ABSTRACT

In this paper, a new framework for semi-automatic feature extraction is developed and applied to highway extraction and vehicle detection from multiple-frame aerial photographs. The basis of the new framework is a geometric deformable model. This model refers to the minimization of an objective function that connects the optimization problem with the propagation of regular curves. The implementation of curve propagation is based on level set theory. Utilizing implicit representation of two-dimensional curve, level set implementation is capable of dealing with topological changes naturally, and the output is independent of the position of the initial curves. In the previous study of the geometric active model, only boundary information is incorporated into the curve propagation process. Leakage is often inevitable wherever weak edge information exists. In this research, region-based information is added into the geometric active contour model and behaves as a constraint. Thereby, the new proposed method has the ability to integrate boundary and region-based information during the curve propagation and successfully solves the leakage problem. Several practical issues such as seed point selection and propagation are also discussed during the application of highway boundary extraction using this method from aerial photographs covering large areas

ABSTRACT SHORELINE MODELING AND EROSION PREDICTION

This paper presents a shoreline-erosion prediction model of Lake Erie that can forecast shoreline changes from annual to 10-year increments. It was developed by using historical bluffline data of years 1973, 1990, 1994, and 2000 at Lake Erie provided by NOAA and local government agencies. The relationships among these historical shorelines are analyzed using a least-squares method. Erosion rates are then derived from shoreline changes. In addition, other influential factors such as changes in terrain and water-levels are also considered in the model

3D GEOPOSITIONING ACCURACY ANALYSIS BASED ON INTEGRATION OF QUICKBIRD AND IKONOS IMAGERY

Stereo high-resolution satellite imagery, such as Space Imaging’s IKONOS (1 m resolution) and DigitalGlobe’s QuickBird (submeter resolution), can provide accurate three-dimensional (3D) mapping products. Based on the rational function model, this study investigated the integration of IKONOS and QuickBird images. One pair of stereo IKONOS images and one pair of stereo QuickBird images, collected in the same region, were used in the study. The 3D geopositioning accuracy from a single IKONOS image and a single QuickBird image was compared with those from stereo IKONOS images, stereo QuickBird images, and the combination of the images. First, 3D geopositioning accuracies of stereo IKONOS and QuickBird images were computed respectively by an improved rational function model with four ground control points. It was found that the accuracy of IKONOS images is at the one-meter level and that of QuickBird is at the sub-meter level, in the same order of their image resolutions. All four images from both pairs were then used together based on the rational function model. The calculated accuracy is at the sub-meter level. In data integration, the imaging geometries of both pairs of images were examined. The feasibility and accuracies of combinations of single IKONOS and single QuickBird images were investigated. The results show that, with the proper triangulation angle, a single IKONOS image and a single QuickBird image can form a stereo image pair that can provide sub-meter 3D geopositioning accuracy. 1

Geometric Modeling and Processing of QuickBird Stereo Imagery

This paper discusses geometric modelling and photogrammetric processing methods for high-precision mapping using stereo QuickBird images, and reports research results of data processing in an area in Tampa Bay, Florida,. First, a set of panchromatic “Basic ” QuickBird stereo images are evaluated using GPS control points. Systematic errors in the vendor-provided RPCs (Rational Polynomial Coefficients) are found to be 8.8m, 8.7m and 12.6m in the X, Y and Z directions, respectively. Next, a study of the improvement of 3-D geopositioning accuracy is conducted in which a comparison is made between different adjustment models that represent different numbers and configurations of ground control points. The comparison results indicate that a simple adjustment model with only a couple of ground control points is effective for the elimination of systematic errors and for the improvement of 3-D geopositioning accuracy to a 0.7-1m (1-1.5 pixel) level. In addition, a sub-pixel accuracy of 3-D measurement can be achieved for feature points in images that can be sharply identified and, thus, accurately measured. Based on this improved geometric model, a 3-D shoreline was produced semi-automatically in the area

On-Site Coastal Decision Making With Wireless Mobile GIS

Coastal mapping and shoreline change detection are critical to many applications, including navigation, coastal zone management, coastal environmental protection, and sustainable development. Field surveying and on-site investigation become inevitable to ensure the quality of coastal decision making. To provide innovative tools for governmental agencies to increase efficiency and reduce operation costs, a wireless mobile GIS is developed and applied to on-site decision making for coastal management. This wireless mobile GIS system has three components: a coastal-structure permit subsystem; a shoreline erosion awareness subsystem; and a wireless on-site spatial subsystem. The coastal-structure permit subsystem has been implemented to simulate, in a GIS environment, the decision-making process for granting construction permits for coastal protection structures. The web-based shoreline erosion awareness subsystem has been developed to aid local residents in making land-use decisions. It is implemented both to describe the extent of historic shorelines and previous erosion and to predict future shoreline change due to erosion. The wireless on-site spatial subsystem helps government officials remotely access and update spatial data from field, thus allowing for decision making in real time. This system has been developed in the United States based on the environment at Lake Erie, Ohio

Geometric modelling and photogrammetric processing of high-resolution satellite imagery

The latest generation of high-resolution commercial imaging satellites, such as IKONOS and QuickBird, has opened a new era of earth observation and digital mapping. This paper presents the geometric modeling principles and photogrammetric processing methods involved in high-precision mapping using stereo IKONOS and QuickBird images. First, the imaging geometry and systematic errors in the Rational Function-based sensor model are described. Then the results of a comparison study of IKONOS and QuickBird geopositioning accuracy improvement in which different adjustment models, as well as different number and configuration of ground control points, are presented. Results indicate that a simple adjustment model (e.g., Affine or Scale & Translation) is effective for elimination of the systematic errors found in vendor-provided RFCs (Rational Function Coefficients) and for improvement of 3D geopositioning accuracies to a 1-2m level for IKONOS images and a 0.6-1m level for QuickBird images. For coastal mapping purposes, a semi-automatic 3D shoreline extraction method is proposed. In this method, a 2D shoreline is extracted by manual digitizing on one QuickBird image; then corresponding shoreline points on the other image of the stereo pair are automatically extracted by image matching. The 3D shoreline is computed using photogrammetric triangulation with the improved geometric model

Implementation of A Coastal Decision Making System using Internet and Wireless Technologies

This paper presents results of a coastal decision making system that utilizes the following tools: Internet, wireless technology, and Geographic Information Systems (GIS). The developed system consists of an on-site mobile spatial subsystem, a coastal structure permitting subsystem, and a web-based shoreline erosion awareness subsystem. The system is being tested and developed for applications in the Lake Erie, Ohio and will be adapted to the Tampa Bay, Florida area. 1