用Rails / PostGIS / RGeo存储数据
用Rails / PostGIS / RGeo存储数据
提问于 2016-12-24 19:06:27
在使用丹尼尔·祖马(氏)溶液 / Rails处理Google数据时难以实现RGeo。
设置
位置表：
create_table "locations", force: :cascade do |t|
t.string "name",
t.geometry "polygon", limit: {:srid=>3857, :type=>"polygon"}
end位置类：
class Location < ActiveRecord::Base
# Create a simple mercator factory. This factory itself is
# geographic (latitude-longitude) but it also contains a
# companion projection factory that uses EPSG 3857.
FACTORY = RGeo::Geographic.simple_mercator_factory
# To interact in projected coordinates,
# just use the "polygon" attributes directly.
def polygon_projected
self.polygon
end
def polygon_projected=(value)
self.polygon = value
end
# To use geographic (lat/lon) coordinates,
# convert them using the wrapper factory.
def polygon_geographic
FACTORY.unproject(self.polygon)
end
def polygon_geographic=(value)
self.polygon = FACTORY.project(value)
end
def self.from_geojson(geojson)
location = Location.new
decoded_polygon = RGeo::GeoJSON.decode(geojson, json_parser: :json, geo_factory: RGeo::Geographic.simple_mercator_factory)
location.polygon_geographic = decoded_polygon
return location
end
endinitializers/rgeo.rb:
RGeo::ActiveRecord::SpatialFactoryStore.instance.tap do |config|
# By default, use the GEOS implementation for spatial columns.
config.default = RGeo::Geos.factory_generator
end(从这里和这里派生的解决方案)
问题
因此，我们开始-我创建一个新的位置对象从一个geojson形状包含坐标从谷歌地图：
manhattan_polygon_data = '{"type":"Polygon","coordinates":[[[-73.9784998975546,40.7367992185915],[-73.9808911983494,40.7334453322506],[-73.9899687850649,40.7350399153528],[-73.9894998975546,40.7395992185915]]]}'
location = Location.from_geojson(manhattan_polygon_data)此时，我们所有的地理属性都在正常工作：
# Test geo properties:
location.polygon_projected
=> #<RGeo::Geos::CAPIPolygonImpl:0x3fc428c0c7dc "POLYGON ((-8235248.938246019 4973596.780357394, -8235515.136632829 4973104.057720993, -8236525.648963631 4973338.316345756, -8236473.452644745 4974008.150049943, -8235248.938246019 4973596.780357394))">
location.polygon_geographic
=> #<RGeo::Geographic::ProjectedPolygonImpl:0x3fc425d137a0 "POLYGON ((-73.9784998975546 40.73679921859151, -73.9808911983494 40.73344533225058, -73.9899687850649 40.73503991535281, -73.9894998975546 40.73959921859151, -73.9784998975546 40.73679921859151))">但是当我们从数据库中保存和重新读取数据时，有些地方出错了：
# Save and retrieve from DB:
location.save!
location_from_db = Location.find(location.id)
# Test geo properties again:
location_from_db.polygon_projected
=> #<RGeo::Geos::CAPIPolygonImpl:0x3fc425cfb664 "POLYGON ((-8235248.938246019 4973596.780357394, -8235515.136632829 4973104.057720993, -8236525.648963631 4973338.316345756, -8236473.452644745 4974008.150049943, -8235248.938246019 4973596.780357394))">
location_from_db.polygon_geographic
RGeo::Error::InvalidGeometry: You can unproject only features that are in the projected coordinate space.
from /usr/local/lib/ruby/gems/2.3.0/gems/rgeo-0.5.3/lib/rgeo/geographic/factory.rb:270:in `unproject'考虑到两个对象的投影几何是等价的，我不知道为什么后一个unproject操作失败。
回答 1
Stack Overflow用户
回答已采纳
发布于 2016-12-25 17:29:30
在这里找到我的答案：简单的Mercator工厂项目/Unproject- Google组
问题是，与ActiveRecord适配器使用的属性相比，我对属性使用的是不同的工厂实例。解决方案是在初始化器中创建简单mercator工厂的单个实例。
位置类：
class Location < ActiveRecord::Base
# To interact in projected coordinates,
# just use the "polygon" attributes directly.
def polygon_projected
self.polygon
end
def polygon_projected=(value)
self.polygon = value
end
# To use geographic (lat/lon) coordinates,
# convert them using the wrapper factory.
def polygon_geographic
FACTORY.unproject(self.polygon)
end
def polygon_geographic=(value)
self.polygon = FACTORY.project(value)
end
def self.from_geojson(geojson)
location = Location.new
decoded_polygon = RGeo::GeoJSON.decode(geojson, json_parser: :json, geo_factory: RGeo::Geographic.simple_mercator_factory)
location.polygon_geographic = decoded_polygon
return location
end
endinitializers/rgeo.rb:
# Create a single instance of simple mercator factory.
# This factory itself is geographic (latitude-longitude)
# but it also contains a companion projection factory that uses EPSG 3857.
FACTORY = RGeo::Geographic.simple_mercator_factory
RGeo::ActiveRecord::SpatialFactoryStore.instance.tap do |config|
config.default = FACTORY.projection_factory
end页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/41316122
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