wkt(OGC well-known text)和wkb(OGC well-known binary)是OGC制定的空间数据的组织规范，wkt是以文本形式描述，wkb是以二进制形式描述。
使用wkt和wkb能够很好到和其他系统进行数据交换，目前大部分支持空间数据存储的数据库构造空间数据都采用这两种方式。
wkt的组织结构如下：
| Geometry type | Text description | Comment |
| ST_Point | 'point empty' | empty point |
| ST_Point | 'point z empty' | empty point with z-coordinate |
| ST_Point | 'point m empty' | empty point with measure |
| ST_Point | 'point zm empty' | empty point with z-coordinate and measure |
| ST_Point | 'point ( 10.05 10.28 )' | point |
| ST_Point | 'point z( 10.05 10.28 2.51 )' | point with z-coordinate |
| ST_Point | 'point m( 10.05 10.28 4.72 )' | point with measure |
| ST_Point | 'point zm(10.05 10.28 2.51 4.72 )' | point with z-coordinate and measure |
| ST_LineString | 'linestring empty' | empty linestring |
| ST_LineString | 'linestring z empty' | empty linestring with z-coordinates |
| ST_LineString | 'linestring m empty' | empty linestring with measures |
| ST_LineString | 'linestring zm empty' | empty linestring with z-coordinates and measures |
| ST_LineString | 'linestring (10.05 10.28 , 20.95 20.89 )' | linestring |
| ST_LineString | 'linestring z(10.05 10.28 3.09, 20.95 31.98 4.72, 21.98 29.80 3.51 )' | linestring with z-coordinates |
| ST_LineString | 'linestring m(10.05 10.28 5.84, 20.95 31.98 9.01, 21.98 29.80 12.84 )' | linestring with measures |
| ST_LineString | 'linestring zm(10.05 10.28 3.09 5.84, 20.95 31.98 4.72 9.01, 21.98 29.80 3.51 12.84)' | linestring with z-coordinates and measures |
| ST_Polygon | 'polygon empty' | empty polygon |
| ST_Polygon | 'polygon z empty' | empty polygon with z-coordinates |
| ST_Polygon | 'polygon m empty' | empty polygon with measures |
| ST_Polygon | 'polygon zm empty' | empty polygon with z-coordinates and measures |
| ST_Polygon | 'polygon ((10 10, 10 20, 20 20, 20 15, 10 10))' | polygon |
| ST_Polygon | 'polygon z((10 10 3, 10 20 3, 20 20 3, 20 15 4, 10 10 3))' | polygon with z-coordinates |
| ST_Polygon | 'polygon m((10 10 8, 10 20 9, 20 20 9, 20 15 9, 10 10 8 ))' | polygon with measures |
| ST_Polygon | 'polygon zm((10 10 3 8, 10 20 3 9, 20 20 3 9, 20 15 4 9, 10 10 3 8 ))' | polygon with z-coordinates and measures |
| ST_MultiPoint | 'multipoint empty' | empty multipoint |
| ST_MultiPoint | 'multipoint z empty' | empty multipoint with z-coordinates |
| ST_MultiPoint | 'multipoint m empty' | empty multipoint with measures |
| ST_MultiPoint | 'multipoint zm empty' | empty multipoint with z-coordinates and measures |
| ST_MultiPoint | 'multipoint (10 10, 20 20)' | multipoint with two points |
| ST_MultiPoint | 'multipoint z(10 10 2, 20 20 3)' | multipoint with z-coordinates |
| ST_MultiPoint | 'multipoint m(10 10 4, 20 20 5)' | multipoint with measures |
| ST_MultiPoint | 'multipoint zm(10 10 2 4, 20 20 3 5)' | multipoint with z-coordinates and measures |
| ST_MultiLineString | 'multilinestring empty' | empty multilinestring |
| ST_MultiLineString | 'multilinestring z empty' | empty multilinestring with z-coordinates |
| ST_MultiLineString | 'multilinestring m empty' | empty multilinestring with measures |
| ST_MultiLineString | 'multilinestring zm empty' | empty multilinestring with z-coordinates and measures |
| ST_MultiLineString | 'multilinestring ((10.05 10.28 , 20.95 20.89 ),( 20.95 20.89, 31.92 21.45))' | multilinestring |
| ST_MultiLineString | 'multilinestring z((10.05 10.28 3.4, 20.95 20.89 4.5),( 20.95 20.89 4.5, 31.92 21.45 3.6))' | multilinestring with z-coordinates |
| ST_MultiLineString | 'multilinestring m((10.05 10.28 8.4, 20.95 20.89 9.5), (20.95 20.89 9.5, 31.92 21.45 8.6))' | multilinestring with measures |
| ST_MultiLineString | 'multilinestring zm((10.05 10.28 3.4 8.4, 20.95 20.89 4.5 9.5), (20.95 20.89 4.5 9.5, 31.92 21.45 3.6 8.6))' | multilinestring with z-coordinates and measures |
| ST_MultiPolygon | 'multipolygon empty' | empty multipolygon |
| ST_MultiPolygon | 'multipolygon z empty' | empty multipolygon with z-coordinates |
| ST_MultiPolygon | 'multipolygon m empty' | empty multipolygon with measures |
| ST_MultiPolygon | 'multipolygon zm empty' | empty |
| ST_MultiPolygon | 'multipolygon (((10 10, 10 20, 20 20, 20 15 , 10 10), (50 40, 50 50, 60 50, 60 40, 50 40)))' | multipolygon |
| ST_MultiPolygon | 'multipolygon z(((10 10 7, 10 20 8, 20 20 7, 20 15 5, 10 10 7), (50 40 6, 50 50 6, 60 50 5, 60 40 6, 50 40 6)))' | multipolygon with z-coordinates |
| ST_MultiPolygon | 'multipolygon m(((10 10 2, 10 20 3, 20 20 4, 20 15 5, 10 10 2), (50 40 7, 50 50 3, 60 50 4, 60 40 5, 50 40 7)))' | multipolygon with measures |
| ST_MultiPolygon | 'multipolygon zm(((10 10 7 2, 10 20 8 3, 20 20 7 4, 20 15 5 5, 10 10 7 2), (50 40 6 7, 50 50 6 3, 60 50 5 4, 60 40 6 5, 50 40 6 7)))' | multipolygon with z-coordinates and measures |
wkb的组织结构如下：
基本类型定义：
byte : 1 byte
uint32 : 32 bit unsigned integer (4 bytes)
double : double precision number (8 bytes)
Building Blocks : Point, LinearRing
Point {
double x;
double y;
};
LinearRing {
uint32 numPoints;
Point points[numPoints];
}
enum wkbGeometryType {
wkbPoint = 1,
wkbLineString = 2,
wkbPolygon = 3,
wkbMultiPoint = 4,
wkbMultiLineString = 5,
wkbMultiPolygon = 6,
wkbGeometryCollection = 7
};
enum wkbByteOrder {
wkbXDR = 0, Big Endian
wkbNDR = 1 Little Endian
};
WKBPoint {
byte byteOrder;
uint32 wkbType; 1
Point point;
}
WKBLineString {
byte byteOrder;
uint32 wkbType; 2
uint32 numPoints;
Point points[numPoints];
}
WKBPolygon {
byte byteOrder;
uint32 wkbType; 3
uint32 numRings;
LinearRing rings[numRings];
}
WKBMultiPoint {
byte byteOrder;
uint32 wkbType; 4
uint32 num_wkbPoints;
WKBPoint WKBPoints[num_wkbPoints];
}
WKBMultiLineString {
byte byteOrder;
uint32 wkbType; 5
uint32 num_wkbLineStrings;
WKBLineString WKBLineStrings[num_wkbLineStrings];
}
wkbMultiPolygon {
byte byteOrder;
uint32 wkbType; 6
uint32 num_wkbPolygons;
WKBPolygon wkbPolygons[num_wkbPolygons];
}
WKBGeometry {
union {
WKBPoint point;
WKBLineString linestring;
WKBPolygon polygon;
WKBGeometryCollection collection;
WKBMultiPoint mpoint;
WKBMultiLineString mlinestring;
WKBMultiPolygon mpolygon;
}
};
WKBGeometryCollection {
byte byte_order;
uint32 wkbType; 7
uint32 num_wkbGeometries;
WKBGeometry wkbGeometries[num_wkbGeometries]
}
下面是一个point(1,1) 使用WKB存储的例子：
0101000000000000000000F03F000000000000F03F
这个2进制流可以按照WKBPoint的结构进行拆分：
Byte order : 01
WKB type : 01000000
X : 000000000000F03F
Y : 000000000000F03F
byte order要么为0，要么为1，0为使用little-endian编码(NDR)，1为使用big-endian编码(XDR)。
WKB type 是几何类型，在wkbGeometryType中定义. 值为1-7，分别对应 Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection.
x,y为点的坐标值，为double类型。