Re: earthdistance is not giving correct results.

I agree, NS or EW long lat should be the same.
I was just pointing to the wrong figure.  Also, if ll_to_earth takes lat
first, it should report an error for a |lat| > 90...


Michael Fuhr wrote:
> On Sat, Oct 02, 2004 at 09:29:16PM -0400, Jean-Luc Lachance wrote:
>
>>Maybe it would work with the right long & lat...
>>try
>>Protland OR -122.67555, 45.51184
>>Seattle WA -122.32956, 47.60342
>
>
> It doesn't matter which hemisphere the longitudes are in as long
> as they're in the same hemisphere:
>
> test=> select earth_distance(ll_to_earth('122.55688','45.513746'),ll_to_earth('122.396357','47.648845'));
>   earth_distance
> ------------------
>  128862.563227506
> (1 row)
>
> test=> select earth_distance(ll_to_earth('-122.55688','45.513746'),ll_to_earth('-122.396357','47.648845'));
>   earth_distance
> ------------------
>  128862.563227506
> (1 row)
>
> What *does* matter is that one specify (lat, lon) instead of
> (lon, lat):
>
> test=> select earth_distance(ll_to_earth('45.513746', '122.55688'),ll_to_earth('47.648845', '122.396357'));
>   earth_distance
> ------------------
>  237996.256627247
> (1 row)
>
> That's 238km, or about 148mi; using your coordinates gives almost
> the same answer, about 234km or 146mi.  As I said, the distance
> between Portland and Seattle is around 150mi.
>
>
>>Also, do not forget that it is the line distance not the driving distance.
>
>
> I doubt anybody thought that earth_distance() was calculating driving
> distance.  How would it know what route to follow without an extensive
> road database and a route specification?
>