From: | Paul Ramsey <pramsey(at)cleverelephant(dot)ca> |
---|---|
To: | Jeff Herrin <jeff(at)openhotel(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: earthdistance compass bearing |
Date: | 2013-06-18 18:58:57 |
Message-ID: | 6562BD8BEB964F078F2A8B122C4FDF41@cleverelephant.ca |
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Thread: | |
Lists: | pgsql-general |
The code for azimuth on a sphere isn't so gnarly you couldn't whip it up in plpgsql,
http://trac.osgeo.org/postgis/browser/trunk/liblwgeom/lwgeodetic.c#L924
P.
--
Paul Ramsey
http://cleverelephant.ca
http://postgis.net
On Tuesday, June 18, 2013 at 11:16 AM, Jeff Herrin wrote:
> I don't need it to be too accurate. We're pushing hotel info into the GDS (sabre, expedia, orbitz, etc). They require airport info relative to the hotel. Example: DFW is 25 miles NW of the property. I thought about just faking it...comparing the hotel's lat/long from the airports. I can probably get N,S,E,W reliably enough, but i'm not sure at what point N becomes NW, etc. That just seems like a really crude bad way to do it, but the alternatives seem unnecessarily complex. I found some examples that use bearing but they all take headings in degrees (which im not seeing in earthdistance). I guess I'm going to have to either setup postGIS or brush up on my trig.
>
> thanks,
> altimage
>
> From: "Steve Crawford" <scrawford(at)pinpointresearch(dot)com (mailto:scrawford(at)pinpointresearch(dot)com)>
> To: "Jeff Herrin" <jeff(at)openhotel(dot)com (mailto:jeff(at)openhotel(dot)com)>
> Cc: pgsql-general(at)postgresql(dot)org (mailto:pgsql-general(at)postgresql(dot)org)
> Sent: Tuesday, June 18, 2013 11:37:10 AM
> Subject: Re: [GENERAL] earthdistance compass bearing
>
> On 06/18/2013 10:42 AM, Jeff Herrin wrote:
> > I'm trying to get a compass bearing (N,S,NW,etc) using earthdistance. I can successfully get the distance between 2 points using either the point or cube method, but I've been struggling with getting the bearing. Any tips?
>
>
> PostGIS has some functions that may be of use but might be overkill depending on your use but I don't see anything in earthdistance.
>
> What are you trying to solve?
>
> It's one thing if you are looking for a one-degree-accurate magnetic-variation-compensated great-circle heading for a 6,000km flight using WGS84 projection (initial-heading, of course, as it will vary over the course of your travel).
>
> If you just want to be accurate to eight compass-points over a few city-blocks then simple trig is probably more than sufficient.
>
> Cheers,
> Steve
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