GIS中的WKB介紹

GIS中的WKB介紹

WKB的全稱是The Well-known Binary，也簡稱WKB，OGC與ISO/TC211都做出了一樣的規(guī)范，它是用來幾何體的表達(dá)。即用連續(xù)的2進(jìn)制流來表達(dá)幾何體，這樣在GIS互操作方面也有好處?，F(xiàn)代GIS軟件的底層模塊中可以說都有關(guān)于WKB解析代碼。在2進(jìn)制存儲(chǔ)中有大尾端和小尾端之分，通常在2進(jìn)制流的第1個(gè)字節(jié)就指定，這樣在這個(gè)字節(jié)以后的字節(jié)流就能夠依照相應(yīng)的大小尾端模式進(jìn)行解析。分大小尾端是為了適應(yīng)不同平臺(tái)環(huán)境。在1些開源和商業(yè)GIS軟件中都支持幾何體的WKB表示，這樣做也是為了異構(gòu)平臺(tái)之間互操作。

基本塊的定義以下，這些基本定義在后面的幾何體建模中會(huì)用到：

Point {

double  x;

double  y}

PointZ {

double  x;

double  y;

double  z}

PointM {

double  x;

double  y;

double  m}

PointZM{

double  x;

double  y;

double  z;

double  m}

LinearRing{

uint32  numPoints;

Point  points[numPoints]}

LinearRingZ{

uint32  numPoints;

PointZ  points[numPoints]}

LinearRingM{

uint32  numPoints;

PointM  points[numPoints]}

LinearRingZM{

uint32  numPoints;

PointZM  points[numPoints]}

//字節(jié)序

enum  WKBByteOrder {

wkbXDR =0, // 大尾端

wkbNDR =1 // 小尾端

}

下面表示幾何體的整型的數(shù)值，用枚舉表示。

enum  WKBGeometryType {

wkbPoint  = 1,

wkbLineString  = 2,

wkbPolygon  = 3,

wkbTriangle  = 17

wkbMultiPoint  = 4,

wkbMultiLineString  = 5,

wkbMultiPolygon  = 6,

wkbGeometryCollection  = 7,

wkbPolyhedralSurface  = 15,

wkbTIN  = 16

wkbPointZ  = 1001,

wkbLineStringZ  = 1002,

wkbPolygonZ  = 1003,

wkbTrianglez = 1017

wkbMultiPointZ  = 1004,

wkbMultiLineStringZ  = 1005,

wkbMultiPolygonZ  = 1006,

wkbGeometryCollectionZ  = 1007,

wkbPolyhedralSurfaceZ  = 1015,

wkbTINZ  = 1016

wkbPointM  = 2001,

wkbLineStringM  = 2002,

wkbPolygonM  = 2003,

wkbTriangleM  = 2017

wkbMultiPointM  = 2004,

wkbMultiLineStringM  = 2005,

wkbMultiPolygonM  = 2006,

wkbGeometryCollectionM  = 2007,

wkbPolyhedralSurfaceM  = 2015,

wkbTINM  = 2016

wkbPointZM  = 3001,

wkbLineStringZM  = 3002,

wkbPolygonZM  = 3003,

wkbTriangleZM  = 3017

wkbMultiPointZM  = 3004,

wkbMultiLineStringZM  = 3005,

wkbMultiPolygonZM  = 3006,

wkbGeometryCollectionZM  = 3007,

wkbPolyhedralSurfaceZM  = 3015,

wkbTinZM  = 3016,

}

以下就是各個(gè)幾何體的定義了。

(1)   點(diǎn)

主要包括字節(jié)序和幾何體類型，接著后面是坐標(biāo)總共是1+4+16=21個(gè)字節(jié)

WKBPoint{

byte  byteOrder;                        //字節(jié)序

static  uint32  wkbType= 1;             //幾何體類型

Point  point}                             //點(diǎn)的坐標(biāo)

WKBPointZ{

byte  byteOrder;

static  uint32  wkbType = 1001;

PointZ  point}

WKBPointM{

byte  byteOrder;

static  uint32  wkbType= 2001;

PointM  point}

WKBPointZM{

byte  byteOrder;

static  uint32  wkbType= 3001;

PointZM  point}

（2）線串，即折線

WKBLineString{

byte  byteOrder;                               //字節(jié)序

static  uint32  wkbType = 2;                    //幾何體類型

uint32  numPoints;                                  //點(diǎn)的個(gè)數(shù)

Point  points[numPoints]}                 //點(diǎn)的坐標(biāo)數(shù)組

總的字節(jié)大小

1+4+4+ numPoints*sizeof(Point)字節(jié)

WKBLineStringZ{

byte  byteOrder;

static  uint32  wkbType = 1002;

uint32  numPoints;

PointZ  points[numPoints]}

WKBLineStringM{

byte  byteOrder;

static  uint32  wkbType= 2002;

uint32  numPoints;

PointM  points[numPoints]}

WKBLineStringZM{

byte  byteOrder;

static  uint32  wkbType= 3002;

uint32  numPoints;

PointZM  points[numPoints]}

(2)   多邊形

所占的字節(jié)大小是：1+4+4+ numRings*(4 + LinearRing.numPoints*sizeof(Point))

WKBPolygon{

byte  byteOrder;                               //字節(jié)序

static  uint32  wkbType= 3;                    //幾何體類型

uint32  numRings;                                   //線串的個(gè)數(shù)

LinearRing rings[numRings]}           //線串（環(huán)）的數(shù)組

WKBPolygonZ{

byte  byteOrder;

static  uint32  wkbType= 1003;

uint32  numRings;

LinearRingZ  rings[numRings]}

WKBPolygonM{

byte  byteOrder;

static  uint32  wkbType = 2003;

uint32  numRings;

LinearRingM  rings[numRings]}

WKBPolygonZM{

byte  byteOrder;

static  uint32  wkbType = 3003;

uint32  numRings;

LinearRingZM  rings[numRings]}

（4）3角形注：當(dāng)前主流GIS軟件中把這個(gè)放在TIN中建模

WKBTriangle{

byte  byteOrder;                               //字節(jié)序

static  uint32  wkbType= 17;                  //幾何體的類型

uint32  numRings;                                   //環(huán)的個(gè)數(shù)

LinearRing rings[numRings]}           //環(huán)的數(shù)組

WKBTriangleZ{

byte  byteOrder;

static  uint32  wkbType= 1017;

uint32  numRings;

LinearRingZ rings[numRings]}

WKBTriangleM{

byte  byteOrder;

Static  uint32  wkbType= 2017;

uint32  numRings;

LinearRingM  rings[numRings]}

WKBTriangleZM{

Byte  byteOrder;

static  uint32  wkbType= 3017;

uint32  numRings;

LinearRingZM  rings[numRings]}

(5)多面體表面

WKBPolyhedralSurface{

bytebyteOrder;                                        //字節(jié)序

staticuint32 wkbType = 15;                       //幾何體類型

uint32numPolygons;                                //多邊形數(shù)目

WKBPolygonpolygons[numPolygons]}      //多邊形的數(shù)組

WKBPolyhedralSurfaceZ{

bytebyteOrder;

staticuint32 wkbType=1015;

uint32numPolygons;

WKBPolygonZpolygons[numPolygons]}

WKBPolyhedralSurfaceM{

bytebyteOrder;

staticuint32 wkbType=2015;

uint32numPolygons;

WKBPolygonMpolygons[numPolygons]}

WKBPolyhedralSurfaceZM{

bytebyteOrder;

staticuint32 wkbType=3015;

uint32numPolygons;

WKBPolygonZMpolygons[numPolygons]}

（6）不規(guī)則3角網(wǎng)（TIN）貌似1般3角網(wǎng)和矢量數(shù)據(jù)的幾何模型位于同1層次上，所以目前很少看到有GIS軟件這樣建模的。僅僅是自己的觀點(diǎn)

WKBTIN {

bytebyteOrder;                                               //字節(jié)序

staticuint32 wkbType = 16;                              //幾何體的類型

uint32numPolygons;                                       //多邊形的數(shù)目

WKBPolygonpolygons[numPolygons]}             //多邊形數(shù)組

WKBTINZ{

bytebyteOrder;

staticuint32 wkbType=1016;

uint32numPolygons;

WKBPolygonZpolygons[numPolygons]}

WKBTINM{

bytebyteOrder;

staticuint32 wkbType=2016;

uint32numPolygons;

WKBPolygonMpolygons[numPolygons]}

WKBTINZM{

bytebyteOrder;

staticuint32 wkbType=3016;

uint32numPolygons;

WKBPolygonZMpolygons[numPolygons]}

(7)多點(diǎn)

WKBMultiPoint{

byte  byteOrder;                               //字節(jié)序

staticuint32 wkbType=4;                    //幾何體類型

uint32  numPoints;                                  //點(diǎn)的個(gè)數(shù)

WKBPoint points[numPoints]}         //點(diǎn)的數(shù)組

WKBMultiPointZ{

Byte  byteOrder;

Static  uint32  wkbType=1004;

uint32  numPoints;

WKBPointZ  points[numPoints]}

WKBMultiPointM{

byte  byteOrder;

static  uint32  wkbType=2004;

uint32  numPoints;

WKBPointM  points[numPoints]}

WKBMultiPointZM{

byte  byteOrder;

Static  uint32  wkbType=3004;

uint32  numPoints;

WKBPointZM  points[numPoints]}

（8）多線串

WKBMultiLineString{

byte  byteOrder;                                                    //字節(jié)序

staticuint32 wkbType = 5;                                       //幾何體類型

uint32  numLineStrings;                                        //線串的個(gè)數(shù)

WKBLineString  lineStrings[numLineStrings]}         //線串?dāng)?shù)組

WKBMultiLineStringZ{

byte  byteOrder;

static  uint32  wkbType= 1005;

uint32  numLineStrings;

WKBLineStringZ  lineStrings[numLineStrings]}

WKBMultiLineStringM{

byte  byteOrder;

static  uint32  wkbType = 2005;

uint32  numLineStrings;

WKBLineStringM  lineStrings[numLineStrings]}

WKBMultiLineStringZM{

byte  byteOrder;

static  uint32  wkbType = 3005;

uint32  numLineStrings;

WKBLineStringZM  lineStrings[numLineStrings]}

（9）多多邊形

WKBMultiPolygon{

bytebyteOrder;                                        //字節(jié)序

staticuint32 wkbType = 6;                         //幾何體類型

uint32numPolygons;                                //多邊形數(shù)目

WKBPolygonpolygons[numPolygons]}      //多邊形數(shù)組

WKBMultiPolygonZ{

bytebyteOrder;

staticuint32 wkbType = 1006;

uint32numPolygons;

WKBPolygonZpolygons[numPolygons]}

WKBMultiPolygonM{

bytebyteOrder;

staticuint32 wkbType = 2006;

uint32numPolygons;

WKBPolygonMpolygons[numPolygons]}

WKBMultiPolygonZM{

bytebyteOrder;

staticuint32 wkbType = 3006;

uint32numPolygons;

WKBPolygonZMpolygons[numPolygons]}

下圖是1個(gè)多邊形的WKB布局。該圖表示這個(gè)多邊形的WKB存儲(chǔ)是小尾端，有兩個(gè)環(huán)，并且兩個(gè)環(huán)的點(diǎn)的個(gè)數(shù)都是3。