如何转换 Shapefile 的坐标？

发布于 2024-11-28 08:11:28 字数 1029 浏览 0 评论 0原文

我正在尝试将社区数据导入我的应用程序，但我使用的数据存在问题，这些数据是从此处。

该文件包含一个包含旧金山街区的 shapefile。我正在运行 Ruby on Rails 框架，目前正在使用 GeoRuby 来解析 shapefile。

代码如下所示：

def self.run_import
  shpfile = '/path/to/realtor_neighborhoods/realtor_neighborhoods'
  ShpFile.open(shpfile) do |shp|
    shp.each do |shape|
      # This gets the first (and only) Polygon from each MultiPolygon
      polygon = shape.geometry.geometries.first 
      puts polygon.inspect
    end
  end
end

代码能够解析文件，但我无法理解所解释的坐标。所有点的值都以百万计，而我期望坐标在 -180 到 180 之间，以获得有效的纬度和经度。看一个例子：

<GeoRuby::SimpleFeatures::Point:0x00000104566a08 @srid=4326, @with_z=false, \
   @with_m=false, @x=6015402.9999795845, @y=2114960.4999904726, @z=0.0, @m=0.0>,

这些坐标值的格式是什么？我怎样才能将它们转换为对我有意义的值？（即基于 SRID 4326 <=> WGS84 空间参考系统的纬度/经度）

预先感谢您！

原文

I am trying to get neighborhood data into my application, and I'm having problems with the data I am using, which I got from here.

This file contains a shapefile that has the neighborhoods of San Francisco. I am running a Ruby on Rails framework, and I'm currently using GeoRuby to parse the shapefile.

The code looks like this:

def self.run_import
  shpfile = '/path/to/realtor_neighborhoods/realtor_neighborhoods'
  ShpFile.open(shpfile) do |shp|
    shp.each do |shape|
      # This gets the first (and only) Polygon from each MultiPolygon
      polygon = shape.geometry.geometries.first 
      puts polygon.inspect
    end
  end
end

The code is able to parse the file, but I am unable to understand the coordinates as interpreted. All of the points have values in the millions, when I would expect coordinates between -180 and 180, for valid latitude and longitude. Take a look at an example point:

<GeoRuby::SimpleFeatures::Point:0x00000104566a08 @srid=4326, @with_z=false, \
   @with_m=false, @x=6015402.9999795845, @y=2114960.4999904726, @z=0.0, @m=0.0>,

What is the format of these coordinate values? How can I convert them to values that are meaningful to me? (i.e. latitude/longitude based on the SRID 4326 <=> WGS84 spatial reference system)

Thank you in advance!

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再可℃爱ぅ一点好了 2024-12-05 08:11:28

从形状文件中获得的数据是投影地理数据。

从你的问题来看，听起来你真的只是更喜欢以纬度/经度形式显示数据。为此，您需要重新投影数据。我不是一个 ruby 爱好者，但是快速的网络搜索表明 georuby 不支持重投影 http://georuby.rubyforge.org /，但是 rgeo 可以。 http://www.daniel-azuma.com/blog/archives/28

如果您想了解有关地图投影的更多信息，请查看此处。

顺便说一下，有一个面向 GIS（地理信息系统）专家的 stackexchange 网站，名为 http://gis.stackexchange.com

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揪着可爱 2024-12-05 08:11:28

我注意到这仍在获取视图日志。我最终在 RGeo 中苦苦挣扎，但还有另一个解决方案。如果您能够/愿意在执行 ruby 代码之前/之外进行转换，请查看 ogr2ogr。

我在底部的评论中有更多详细信息：
如何使用 (Ruby) RGeo 进行转换（Unproject ) 坐标

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心舞飞扬 2024-12-05 08:11:28

我遇到这个问题是因为我想将 Shapefile 中提供的点从 OSGB36 英国国家网格格式转换为 WGS84 格式（十进制）。我花了很多时间来解决这个问题，所以希望这段代码会很有用。

此代码使用 ffi-ogr gem 并需要 GDAL 库：

require 'ffi-ogr'

data = OGR.read file_name
new_spatial_ref = OGR.import_sr(4326, 'epsg')

data.layers.each do |layer|
  transformer = OGR::CoordinateTransformation.find_transformation(layer.spatial_ref, new_spatial_ref)

  layer.features.each do |feature|
    geometry = OGR::Tools.cast_geometry(feature.geometry)
    geometry.transform(transformer)

    # Do something with geometry here
  end
end

I came across this question as I wanted to transform points supplied in a Shapefile from OSGB36 British National Grid format to WGS84 format (decimal degrees). I spent a lot of time figuring this out so hopefully this code will prove useful.

This code uses the ffi-ogr gem and requires the GDAL library:

require 'ffi-ogr'

data = OGR.read file_name
new_spatial_ref = OGR.import_sr(4326, 'epsg')

data.layers.each do |layer|
  transformer = OGR::CoordinateTransformation.find_transformation(layer.spatial_ref, new_spatial_ref)

  layer.features.each do |feature|
    geometry = OGR::Tools.cast_geometry(feature.geometry)
    geometry.transform(transformer)

    # Do something with geometry here
  end
end

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