postgis 导出 栅格_PostGIS导出指定范围内的栅格数据

针对已经通过PostGIS导入到PostgreSQL中的栅格数据，给定经纬度范围，实现栅格数据的导出。

查询SQL语句如下：

SELECT ST_Union(ST_Clip(rast,geom)) AS rast FROM public.alt CROSS JOIN

ST_MakeEnvelope(90,60,120,45,4326) As geom WHERE ST_Intersects(rast,geom);

其中PostGIS函数的含义如下：

ST_MakeEnvelope：函数用于构造一个矩形范围，其参数分别是最小Ｘ值，最小Ｙ值，最大Ｘ值，最大Ｙ值和坐标系代码

ST_Intersects：函数用于选择出与geom矩形相交的栅格Tiles

ST_Clip：函数用于将选择出来的Tiles进行裁剪，得到geom范围的数据

ST_Union：函数用于聚合选择出来的数据为一个整体

导出TIF格式的SQL语句如下：

SELECT ST_AsTIFF(rast, 'LZW') FROM (SELECT ST_Union(ST_Clip(rast,geom)) AS rast FROM public.alt

CROSS JOIN ST_MakeEnvelope(90,60,120,45,4326) As geom WHERE ST_Intersects(rast,geom)) AS rasttiff;

完整的Python代码如下：

import psycopg2

# Connect to an existing database

conn = psycopg2.connect('host=localhost port=5432 user=postgres password=123456 dbname=rastertest')

# Open a cursor to perform database operations

cur = conn.cursor()

strsql = "SELECT ST_AsTIFF(rast, 'LZW') " \

"FROM (" \

"SELECT ST_Union(ST_Clip(rast,geom)) AS rast " \

"FROM " \

"alt " \

"CROSS JOIN " \

"ST_MakeEnvelope(90,60,120,45,4326) As geom " \

"WHERE ST_Intersects(rast,geom)" \

") AS rasttiff"

cur.execute(strsql)

# Fetch data as Python objects

rasttiff = cur.fetchone()

# Write data to file

if rasttiff is not None:

open('E:/personalfile/cs1/alt_ex1.tif', 'wb').write(str(rasttiff[0]))

# Close communication with the database

cur.close()

conn.close()

具体裁切导出效果如下图所示：

影像导出效果图.png

参考原文链接：