GIS缓冲值度到带有spaceallite的米 [英] GIS buffer value degree to meters with spatiallite

问题描述

我是Spatialite的新手.我有以下查询:

I am new to Spatialite. I have following query:

select A.* 
from linka as A, pointa as B 
where Contains(Buffer(B.Geometry, 100), A.Geometry)

我实际上想创建100米的缓冲区并了解其中包含的链接.

I actually want to create 100 meters buffer and get to know which are the link's are contained by it.

我能够找到插入的'100'实际上是度值，它为我提供了该范围内的输出.

I can able to find the inserted '100' is actually degree value and it's giving me output which are coming in this range.

我也可以在我的查询中输入度值，但是在世界范围内，从度到米/公里的转换并不相同. 我经过许多站点，能够知道1度=大约110公里. 但是从GIS专家和一些参考站点也可以了解到地球上的每个极点都是不同的.

I can put the degree value also in my query but the transformation from degree to meters/kilometers is not same all around the world. I gone through many sites and able to know 1 degree = 110 KM approx. but from GIS expert and some reference sites also get to know at each pole on earth it's different.

例如，对于平面逼近，公制x和y在Alta/挪威的差异在x方向上为34 km，在y方向上为111 km.使用地理坐标时，缓冲区看起来与此类似:
http://extremelysatisfactorytotalitarianism.com/blog/wp-content/uploads/2010/08/tissot_indicatrix_equirectangular_proj.png

For instance, the difference at Alta/Norway between metrical x and y for planar approximation is 34 km in x direction equal 111 km in y direction. The buffer looks similar to this while using geographic coordinates:
http://extremelysatisfactorytotalitarianism.com/blog/wp-content/uploads/2010/08/tissot_indicatrix_equirectangular_proj.png

我构建了将地理数据转换为几何(X，Y坐标格式)数据并在Spatiallite可以理解的地方进行转换的软件.

I build software which convert geographical data to geometrical (X, Y -coordinate format) data and make transformation where Spatiallite can understand.

我还尝试阅读有关SRID的内容，但无法理解如何将其插入查询中.

I also trying to read regarding SRID things but not able to understand how to insert it into my query.

推荐答案

将几何图形临时转换为公制投影(例如UTM) 如果我假设您当前的投影是WGS84，请尝试以下语句

temporary transform your geometry to a metric projection (eg UTM) if i assume your current projection is WGS84 try the following statment

 transform (buffer (transform (B.geometry, #projection), #dist), 4326))

-在#projection中:您的新投影，例如:WGS 84/UTM区域31N的32631(选择适合您区域的投影)

-in #projection: your new projection, eg: 32631 for WGS 84 / UTM zone 31N (choose the projection that fits your Zone)

-in #dist:以米为单位的距离

-in #dist: distance in meters

(WGS84为4326)

(4326 for WGS84)

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