PostgreSQL+PostGIS 函数，为一对（纬度、经度）点提供角度分离
我编写了以下代码（在花了几个小时尝试正确引用之后）：
CREATE FUNCTION ast3angsep(double precision, double precision, double precision, double precision) RETURNS double precision AS $$
SELECT ST_Distance( ST_GeographyFromText('SRID=4326;POINT('||$1||' '||$2||')'), ST_GeographyFromText('SRID=4326;POINT('||$3||' '||$4||')') )/6370986.0/PI()*180.0;
$$
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
这个函数可以工作，但不幸的是，它的精度非常糟糕。似乎应该有一种更简单的方法来做到这一点。我只想将值传递给函数并让它将它们传递给 ST 函数。我完全无法找到一种方法来做到这一点，而不先将它们转换为字符串，这可能是精度损失的原因。
我这样做完全搞砸了吗？
I wrote the following code (after spending a few hours trying to get the quoting correct):
CREATE FUNCTION ast3angsep(double precision, double precision, double precision, double precision) RETURNS double precision AS $
SELECT ST_Distance( ST_GeographyFromText('SRID=4326;POINT('||$1||' '||$2||')'), ST_GeographyFromText('SRID=4326;POINT('||$3||' '||$4||')') )/6370986.0/PI()*180.0;
$
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
This function works but, unfortunately, it's precision is HORRIBLE. It seems like there should be a much simpler way to do this. I just want to pass the values to the function and have it pass them to the ST functions. I was completely unable to find a way of doing this without converting them to string first, which is probably where the loss of precision enters.
Am I doing this totally screwed up?
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不要使用
ST_GeographyFromText转换为字符串并创建点，而是尝试使用 ST_MakePoint< /a> 直接使用函数接收到的值。Instead of converting to strings and creating a point using
ST_GeographyFromText, try using ST_MakePoint directly with the values received by the funciton.