简介
轨迹数据是针对移动对象（Moving Feature）所记录的连续位置变化信息，例如车辆的轨迹、人的轨迹等。轨迹数据是一类典型的时空数据，分析和理解这些轨迹数据能帮助人们进行深入研究。
Ganos Trajectory是对象关系型数据库ADB PG的一个扩展，提供了一组数据类型、函数和存储过程，帮助用户高效地管理、查询和分析时空轨迹数据。
快速入门
- 创建扩展
Create extension ganos_spatialref; Create extension ganos_geometry; Create Extension Ganos_trajectory; - 轨迹的枚举类型
CREATE TYPE leaftype AS ENUM ('STPOINT', 'STPOLYGON'); - 创建轨迹表
Create Table traj_table (id integer, traj trajectory) DISTRIBUTED BY (id); - 插入轨迹数据
insert into traj_table values (1, ST_MakeTrajectory('STPOINT'::leaftype, st_geomfromtext('LINESTRING (114 35, 115 36, 116 37)', 4326), '[2010-01-01 14:30, 2010-01-01 15:30)'::tsrange, '{"leafcount": 3,"attributes" : {"velocity" : {"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"accuracy":{"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"bearing":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]},"acceleration":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]}}}')), (2, ST_MakeTrajectory('STPOINT'::leaftype, st_geomfromtext('LINESTRING (114 35, 115 36, 116 37)', 4326), '2010-01-01 14:30'::timestamp, '2010-01-01 15:30'::timestamp, '{"leafcount": 3,"attributes" : {"velocity" : {"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"accuracy":{"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"bearing":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]},"acceleration":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]}}}')), (3, ST_MakeTrajectory('STPOINT'::leaftype, st_geomfromtext('LINESTRING (114 35, 115 36, 116 37)', 4326),ARRAY['2010-01-01 14:30'::timestamp, '2010-01-01 15:00'::timestamp, '2010-01-01 15:30'::timestamp], '{"leafcount": 3,"attributes" : {"velocity" : {"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"accuracy":{"type":"integer","length":4,"nullable":false,"value":[120, 130, 140]},"bearing":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]},"acceleration":{"type":"float","length":4,"nullable":false,"value":[120, 130, 140]}}}')), (4, ST_MakeTrajectory('STPOINT'::leaftype, st_geomfromtext('LINESTRING (114 35, 115 36, 116 37)', 4326), '[2010-01-01 14:30, 2010-01-01 15:30)'::tsrange, null)); - 创建轨迹索引
--创建轨迹索引，加速时空过滤效率 create index tr_index on traj_table using gist (traj); --空间查询时，加速空间过滤 select id, traj_id from traj_test where st_3dintersects(traj, ST_GeomFromText('POLYGON((116.46747851805917 39.92317964155052,116.4986540687358 39.92317964155052,116.4986540687358 39.94452401711516,116.46747851805917 39.94452401711516,116.46747851805917 39.92317964155052))')); --时间查询时，加速时间过滤 select id, traj_id from traj_text where st_TContains(traj,'2008-02-02 13:30:44'::timestamp,'2008-02-03 17:30:44'::timestamp); --时空查询时，加速时空过滤 select id, traj_id from traj_test where st_3dintersects(traj, ST_GeomFromText('POLYGON((116.46747851805917 39.92317964155052,116.4986540687358 39.92317964155052,116.4986540687358 39.94452401711516,116.46747851805917 39.94452401711516,116.46747851805917 39.92317964155052))'),'2008-02-02 13:30:44'::timestamp,'2008-02-03 17:30:44'::timestamp); - 创建特定维度轨迹索引
--当我们只需要对轨迹进行特定维度分析时，可以只建立特定维度的索引。当我们不关心轨迹的z维时，可以使用trajgist_op_2dt建立二维+时间索引 create index tr_timespan_time_index on traj_table using gist (traj trajgist_op_2dt); --建立特定维度索引后对2维+时间查询效果会更快 select id, traj_id from traj_test where st_2dintersects(traj, ST_GeomFromText('POLYGON((116.46747851805917 39.92317964155052,116.4986540687358 39.92317964155052,116.4986540687358 39.94452401711516,116.46747851805917 39.94452401711516,116.46747851805917 39.92317964155052))'),'2008-02-02 13:30:44'::timestamp,'2008-02-03 17:30:44'::timestamp); --可以同时有多个索引存在，建立任意一个即可支持所有查询，当有多个时将自动选择最优的索引 create index tr_timespan_time_index on trajtab using gist (traj trajgist_op_2d); select id, traj_id from traj_test where st_2dintersects(traj, ST_GeomFromText('POLYGON((116.46747851805917 39.92317964155052,116.4986540687358 39.92317964155052,116.4986540687358 39.94452401711516,116.46747851805917 39.94452401711516,116.46747851805917 39.92317964155052))')); - 查询轨迹
select st_startTime(traj), st_endTime(traj) from traj_table ; st_starttime | st_endtime ---------------------+--------------------- 2010-01-01 14:30:00 | 2010-01-01 15:30:00 2010-01-01 14:30:00 | 2010-01-01 15:30:00 2010-01-01 14:30:00 | 2010-01-01 15:30:00 2010-01-01 14:30:00 | 2010-01-01 15:30:00 2010-01-01 14:30:00 | 2010-01-01 15:30:00 2010-01-01 11:30:00 | 2010-01-01 15:00:00 2010-01-01 11:30:00 | 2010-01-01 15:00:00 2010-01-01 11:30:00 | 2010-01-01 15:00:00 (8 rows) - 轨迹查询
--通过插值函数查询轨迹点的属性 Select ST_velocityAtTime(traj, '2010-01-01 12:45') from traj_table where id > 5; st_velocityattime ------------------- 5 5 4.16666666666667 (3 rows) - 分析轨迹间的相近性
Select ST_euclideanDistance((Select traj From traj_table Where id = 6), (Select traj From traj_table Where id = 7)); st_euclideandistance ---------------------- 0.0334968923954815 (1 row) - 删除扩展
DROP Extension Ganos_Raster; DROP extension ganos_geometry; Drop Extension Ganos_trajectory;
SQL参考
详细SQL参考请参见Trajectory SQL参考。