将PostGIS几何类型从Shapely中导入为Python的几何类型吗? [英] Importing a PostGIS geometry type into Python as a geometry type from Shapely?

问题描述

因此，我遇到了很多路线断开的线串的情况，需要使用Shapely的LineMerge或Union OR PostGIS ST_Union将它们组合在一起.

So I have a situation where I have a ton of Linestrings of a broken up route, where I need to Union them together using Shapely's LineMerge or Union OR PostGIS ST_Union.

我现在的想法是使用Shapely将线串导入为几何类型.合并它们或使用Shapely合并它们，然后导出回到数据库中的结果表.

My idea right now is to use Shapely to import the Linestrings as Geometry types. Union them or merge them using Shapely, and then export back to a results table in the database.

但是，PostGIS数据库中的几何类型只是一堆乱码.喜欢...

However, the geometry type in the PostGIS database is just a bunch of gibberish. Like...

01020000020e61000....

如何使用Shapely将其从数据库转换为Python几何类型，进行一些操作，然后将其导出回数据库?

How can I translate this from the database to a Python geometry type using Shapely, do some manipulations, and then export it back to a database?

当前这是我的代码，它只是立即从数据库中导入该geom对象字符串，并因为它不是Geometry类型而引发错误.

Currently this is my code, its just importing that geom object string from the database right now and throwing errors because it isn't a Geometry type.

def create_shortest_route_geom(shortest_routes):
    conn = connect_to_database()
    cur = conn.cursor()
    shortest_route_geoms = []
    for route in shortest_routes:
        source = str(int(route[1]))
        target = str(int(route[2]))
        query = 'SELECT the_geom FROM public.ways WHERE target_osm = ' + target + ' AND source_osm = ' + source + ' OR target_osm = ' + source + ' AND source_osm = ' + target + ';'
        cur.execute(query)
        total_geom = cur.fetchone()
        for index, node in enumerate(route):
            try:
                source = str(int(node))
                target = str(int(route[index + 1]))
                query = 'SELECT the_geom FROM public.ways WHERE target_osm = ' + target + ' AND source_osm = ' + source + ' OR target_osm = ' + source + ' AND source_osm = ' + target + ';'
                cur.execute(query)
                geom = cur.fetchone()
                query = "SELECT ST_Union("+str(geom[0])+","+str(total_geom[0])+")"
                cur.execute(query)
                total_geom = cur.fetchone()
            except IndexError:
                print "Last element"
        shortest_route_geoms.insert(total_geom)
    return shortest_route_geoms

我可能在这里找到了我的答案，对其进行了深入研究，并将更新我的问题如果我想出了答案，就会给出答案.

推荐答案

形状已经有了用于这个特定的问题.

PostGIS将几何存储为十六进制值.使用Shapely的loads函数以参数hex = True加载它.

PostGIS stores the geometries as HEX values. Use Shapely's loads function to load this with the parameter of hex=True.

特别是...

geom = shapely.wkb.loads(hex_geom[0], hex=True)

请勿使用PostGIS ST_Union，因为您必须一遍又一遍地进行转储和加载才能正常工作. Shapely也使用 linemerge

Don't use PostGIS ST_Union, cause you have to dump and load over and over for this to work. Shapely has that configured as well with linemerge

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