tailieunhanh - Pro Oracle Spatial for Oracle Database 11g P2

For simplicity, in the example we have assumed that a new map is created at the end of every step. This is certainly a possibility, but it is not necessarily the best option. Later in this book, we will discuss data modeling and how to optimize the sequence of operations. In particular, Chapters 8 and 9 cover spatial operators and functions that make it possible to cluster some of the steps in the example into single queries, making the process much simpler and more efficient. | CHAPTER 1 SPATIAL INFORMATION MANAGEMENT 11 For simplicity in the example we have assumed that a new map is creatodottheepdofevery step. This is certainly a possibility but it is not necessarily the best option. Later in this book we will discuss data modeling and how to optimize the sequence of operations. In particular Chapters 8 and 9 cover spatialoperators andfunctionstha t makeitpossibletoclustersomeofthestepsmdie example into s pigle querics m ckingthe procuss muahslmpSetand tea re efficient. StoringSpaaealDataina Database s re Looking at vector data we usually distinguish between the following Points for exxmple the p tote for s ale in Figurel-1 whose spatial description requires only x y coordinates or x y z if 3D is considered s Lines for example roads whose spatial description requires a start coordinate an end coordinate and atx r coeiiml. eotiel rmcdisle cosrdinate s Polygons r tt aieaC. rir tt id ril i m. iii ae eiaisidcscril cd by closed lines Figure 1-2 sUtwssseaampie contaisisp pcmt lme aodeotygua figure corresponds to a small portion of the area used in the previous site selection example. The vector representation here simplified ferconvemtnce Stows c a eisl c eet l creicr u ihiee Issit polygons the built-upaeeas ehthe Ca tthe picmre bcrdero .anSihe sp crte eomoles . Figure 1 -2. Vector representation of the spatial objects in the picture The vector data in Figure 1-2 could be stored in one or multiple tables. The most natural way of looking atthisdata is toidentifydaValayvrr seldol dalal lialdlivrecommori attributes that become data tables. Most spatial databases use a special data type to store spatial data in a database. Let s refer to this typee sdie geemcSa r. Usere aantPd cchlmnfeSlyte geomutey to e database tohle Sc order to state ssatiaiogjectt. 12 CHAPTER 1 SPATIAL INFORMATION MANAGEMENT In this case the choiceoftableswouldbe rathersimple with three main data layers present Road infrastructures Land use and Points