TIGER/SDTS Topology

The Census Bureau is committed to using the Spatial Data Transfer Standard (SDTS) and is developing an extract from the Census TIGER? called the TIGER/SDTS?. A single file of the prototype TIGER/SDTS is now available with which interested data users may experiment. This paper will graphically describe some of the SDTS concepts and census geographic concepts used in the TIGER/SDTS. The Census TIGER? and the TIGER/SDTS? are trademarks of the Bureau of the Census.     

An Implementation Strategy for SDTS Encoding

Any implementation plan for the Spatial Data Transfer Standard (NIST 1992) must include the following minimum set of tasks: conceptual, logical, and format level mappings; verification of the mappings; and systems development. These tasks are used as a guide in formulating specific project plans. For a data producer to implement an encoding capability, the tasks are learning the SDTS, conceptual mapping, module mapping, building sample modules, format mapping, encoding a sample data set, and developing the system. NOTE: This article assumes familiarity with the SDTS constructs of modules, fields, and subfields and the relationship of the SDTS to ISO 8211 (American National Standards Institute 1986).     

The Maps of Tolkien's Middle-earth by Brian Sibley and John Howe; The Lord of the Rings: Weapons and Warfare by Chris Smith; and The Lord of the Rings: The Return of the King Visual Companion by Jude Fisher.

A conceptual design is presented for a lineage meta-data base system that documents data sources and geographic information system (GIS) transformations applied to derive cartographic products. Artificial intelligence techniques of semantic networks are used to organize input-output relationships between map layers, and frames are used for storing lineage attributes characterizing source, intermediate, and product layers. An example indicates that a lineage meta-data base enables GIS users to determine the fitness for use of spatial data sets.     

The TIGER System: Yesterday,Today, and Tomorrow

The TIGER System is many things to many people. At this juncture, the TIGER System has fulfilled the precensus geographic support functions for which the Geography Division designed it. During the next 18 months, the TIGER System will support a number of functions needed to complete the tabulation of the collected data and make those data useful to the numerous constituencies that carry out the myriad tasks that define our lives. Simultaneously with the use of the TIGER System to support the data tabulation and dissemination missions of the Census Bureau, work will be under way to define a framework for the future of this bold new product – and this future looks bright. If the TIGER System is to be judged truly useful outside the Census Bureau, similar planning will need to be going on in offices and institutions across America. This is true especially in the context of geographic information system (GIS) applications involving the digital products of the TIGER System and the demographic data products of the 1990 census.     

基于多源空间数据与空地协同的植被覆盖度估算——以东亚干草草原为例

植被覆盖度是植物生长状态的综合体现,是研究全球变化与植被变化的重要指标。本文基于多源空间数据和地面数据的协同,估算了东亚干草草原木本和草本覆盖度。估算结果表明,多源数据和地面测量数据相融合的方法提高了估算精度;模型对木本覆盖度的估算更稳健;估算结果改善了对草原地区木本覆盖的低估。估算模型有效地反映了草原低矮分散的木本植物,为分析草原大尺度植被覆盖度的格局和动态提供了参考。