Validation of 7 Years in-Flight HY-2A Calibration Microwave Radiometer Products Using Numerical Weather Model and Radiosondes

Haiyang-2A (HY-2A) has been working in-flight for over seven years, and the accuracy of HY-2A calibration microwave radiometer (CMR) data is extremely important for the wet troposphere delay correction (WTC) in sea surface height (SSH) determination. We present a comprehensive evaluation of the HY-2A CMR observation using the numerical weather model (NWM) for all the data available period from October 2011 to February 2018, including the WTC and the precipitable water vapor (PWV). The ERA(ECMWF Re-Analysis)-Interim products from European Centre for Medium-Range Weather Forecasts (ECMWF) are used for the validation of HY-2A WTC and PWV products. In general, a global agreement of root-mean-square (RMS) of 2.3 cm in WTC and 3.6 mm in PWV are demonstrated between HY-2A observation and ERA-Interim products. Systematic biases are revealed where before 2014 there was a positive WTC/PWV bias and after that, a negative one. Spatially, HY-2A CMR products show a larger bias in polar regions compared with mid-latitude regions and tropical regions and agree better in the Antarctic than in the Arctic with NWM. Moreover, HY-2A CMR products have larger biases in the coastal area, which are all caused by the brightness temperature (TB) contamination from land or sea ice. Temporally, the WTC/PWV biases increase from October 2011 to March 2014 with a systematic bias over 1 cm in WTC and 2 mm in PWV, and the maximum RMS values of 4.62 cm in WTC and 7.61 mm in PWV occur in August 2013, which is because of the unsuitable retrieval coefficients and systematic TB measurements biases from 37 GHz band. After April 2014, the TB bias is corrected, HY-2A CMR products agree very well with NWM from April 2014 to May 2017 with the average RMS of 1.68 cm in WTC and 2.65 mm in PWV. However, since June 2017, TB measurements from the 18.7 GHz band become unstable, which led to the huge differences between HY-2A CMR products and the NWM with an average RMS of 2.62 cm in WTC and 4.33 mm in PWV. HY-2A CMR shows high accuracy when three bands work normally and further calibration for HY-2A CMR is in urgent need. Furtherly, 137 global coastal radiosonde stations were used to validate HY-2A CMR. The validation based on radiosonde data shows the same variation trend in time of HY-2A CMR compared to the results from ECMWF, which verifies the results from ECMWF.

Optimizing Shipyard Interim Product Assembly Using a Value Stream Mapping Methodology

Value stream mapping is used to analyze and improve the production flow in many industries, which includes the airplane and automobile industries worldwide. The shipbuilding industry has adopted lean manufacturing techniques. However, the amount of value stream mapping application in the shipbuidling industry is still relatively sparse due to the large variety of interim products and ship types. The aim of this paper is to analyze the interim products of a typical sized commercial shipyard with a product mix of chemical tankers and asphalt barges to demonstrate how a lean transformation can be performed using a shipyard value stream mapping methodology. The case study maps the typcial panel assembly lines of the shipyard and demonstrates the differences between the ship type interim products and using the lean manufacturing methodology developed by the authors to demonstrate how to define and adjust the production facilities using both lean and group technology techniques to create an improved production line which is demonstrated through a future improved value stream map. The main criteria for analyzing and comparing production improvement is through man-hours and duration time. The future value stream map has improvements of up to 50 percent, which demonstrates the importance of adopting a value stream mapping methodology for shipyards aiming to improve world competivity by decreasing production costs, while maintaining and/or improving quality of the ship buidling blocks.

SEAWOLF Design for Modular Construction

There has been much discussion on designing for producibility, new and innovative construction techniques, changing traditional relationships between engineering design and construction planning, and the requirement for new design products providing information beyond the class design system viewpoint to support the construction of interim products. The purpose of this paper is to continue this dialogue and provide some insight into how the design process has changed by offering for discussion, information, or use the specific process that the SEAWOLF design agent is using today in the development of sectional construction drawings.

Advanced Industrial Measurement Systems for Productive Shipbuilding

Modern shipbuilders have embraced the concept of modular construction and are realizing the gains in productivity associated with this method. Further gains in productivity are achieved if these modules are built and erected "neat," that is, without the traditional excess material normally trimmed at erection. Construction of "neat" hull blocks requires rigid control of accuracy throughout the production cycle. Interim products, from fabricated parts to erected hull blocks, must be measured to acceptable tolerances to prevent excessive rework. This paper analyzes viable types of advanced measurement techniques supporting the process requirements of "neat" modular construction. Documentation of costs and difficulties associated with each measurement technique selected are also analyzed. The first part of the paper is a general description and analysis of the systems. The second part describes actual demonstrations of three measurement systems and analyzes them in the shipbuilding environment: digital theodolites, automated photogrammetry, and an optical laser system.

A Group Technology Approach to Master Scheduling of Shipbuilding Projects

This paper describes the current Master Scheduling approach used at National Steel and Shipbuilding Company (NASSCO) in San Diego. Master schedules at NASSCO focus on key interim products involved in ship construction: units, blocks, (on-board) zones, and tests. Network scheduling algorithms (that is, Critical Path) are used. Each interim product has an associated subnet. Categorization by type is used to simplify the task of developing and maintaining activity lists, dependencies (predecessor/successor relationships) and durations for the thousands of activities. Manual level-loading of critical resources is incorporated into and supported by the overall scheduling process. The paper includes some discussion of problems encountered in the implementation of this scheduling approach.

Interim Products and Concepts of Their Management

This paper discusses the progress leading to the development of interim products and proposes their division into four different types of increasing complexity. Database records prepared for each interim product and their material kits are introduced for use in a management system to direct the movement of materials through work stations and to record all administrative data needed to ensure that the vessel will be built within estimates of labor and materials and within the contracted time. In addition, the records of materials, of material kits and of simple interim products are searched and sorted, using database programming, to find items having similar repetitive work processes. Those aforementioned items having these characteristics are collected into groups for their manufacture in specially equipped work stations of a ship's production system. The commercial shipbuilding practices forming the basis for the majority of available references have favored the paper's emphasis on merchant ship construction. Most of the ideas presented can be readily applied to naval shipbuilding.

Interim Products—An Essential Innovation in Shipyards

Ships of the same kind built in series are not a panacea for lagging productivity. The solution is more fundamental and imaginative. The solution involves a rethinking of an entire shipbuilding system. The world's most productive shipbuilders employ "standard" series interim products made possible by a production system that classifies parts, subassemblies, and assemblies by the problems inherent in their manufacture. The result is highly rationalized design modules and highly organized work. Such interim products are flexible enough to be parts of many sizes and types of ships. Runs of such interim products, not ships, is the key! Research managed and cost-shared by the Los Angeles Division of Todd Pacific Shipyards Corp. for the Maritime Administration created National Shipbuilding Research Program (NSRP) has motivated the current revolution in U.S. shipbuilding methods even for building warships. Guidance was provided by Panel SP-2 of the Ship Production Committee of The Society of Naval Architects and Marine Engineers.