tailieunhanh - Quantitative Methods and Applications in GIS - Chapter 2

Chương này thảo luận về một trong những nhiệm vụ cơ bản gặp thường xuyên nhất trong phân tích không gian: đo khoảng cách và thời gian. Sau khi tất cả, không gian phân tích về các hoạt động thể chất và con người khác nhau trong không gian - nói cách khác, làm thế nào các hoạt động này thay đổi theo khoảng cách từ địa điểm tham chiếu hoặc các đối tượng quan tâm. Trong nhiều ứng dụng, một khi đo khoảng cách hoặc thời gian thu được, các nghiên cứu có thể được hoàn thành bên ngoài. | 2 Measuring Distances and Time This chapter discusses one of basic tasks encountered most often in spatial analysis measuring distances and time. After all spatial analysis is about how physical and human activities vary across space in other words how these activities change with distances from reference locations or objects of interest. In many applications once the distance or time measure is obtained studies may be completed outside a GIS environment. The advancement and wide availability of GIS have made the task much easier than it used to be. The task of distance or time estimation can be found throughout this book. For example spatial smoothing and spatial interpolation in Chapter 3 utilize distance measures to determine which objects enter the computation and how much the objects influence the computation. In trade area analysis in Chapter 4 distances or time between stores and consumers dictate which stores are the closest and how often residents visit a store. In Chapter 5 on accessibility measures distance or time measures are the building block of either the floating catchment area method or the gravity-based method. Chapter 6 examines how population density or land use intensity declines with distance from a city or regional center. The task can also be found in other chapters. This chapter is structured as follows. Section provides an overview of various distance measures. Section discusses how to compute the shortest-route distance time through a network and how to implement it in ArcGIS. A case study of measuring the Euclidean and network distances in northeast China is presented in Section . Results from this case study will be used in case study 4B Section . The chapter is concluded with a brief summary in Section . MEASURES OF DISTANCE Distance measures include Euclidean straight-line or air distance Manhattan distance or network distance. Euclidean distance is simply the distance between two points through a straight line.