Comments on: Locate the Nearest Radar Station and Display Radar Images

By: mike

mike — Fri, 06 Nov 2009 20:32:33 +0000

Andrew, have you tried or have any tips on marking a particular point on these images? I’m thinking along the lines of a generated overlay to mark a particular geo location. If I’m thinking correctly, the Lat calc should be consistent, but the Lon calc will differ depending on the Lat.

By: Andrew

Andrew — Fri, 17 Jul 2009 20:44:30 +0000

mike: see http://phpstarter.net/2009/07/merge-image-layers-in-php/

By: mike

mike — Fri, 10 Jul 2009 13:53:44 +0000

any idea how to use PHP to stack everything into a single image? Mine just turns darker with each overlay addition.

By: Jkirby

Jkirby — Sun, 19 Apr 2009 00:21:44 +0000

Andy-

This is very cool. I have adapted this to also build in a Java 2D application. Do you know how to get the “looping” radar to work?

By: Michael Dupuis

Michael Dupuis — Wed, 25 Feb 2009 16:01:28 +0000

Ok, you know… I could have sworn I tried that, and did that correctly, but I must not of. Trying it again, it seems to be working fine. Thanks for clearing that up. I must have messed something up when I tried it before, sorry for the confusion, because if you do the add 3/subtract 3 it works correctly. One of those days I guess.

By: Andrew

Andrew — Wed, 25 Feb 2009 14:55:53 +0000

So you are adding 3 to the latitude and subtracting 3 from the longitude and it’s still not working?

Can’t help you with the SQLite part, but I know you have to make the calculation in the query, because the distance is different for each query.

By: Michael Dupuis

Michael Dupuis — Wed, 25 Feb 2009 14:38:26 +0000

Well I can’t do this in a query, because I’m using SQLite, so I’m doing this in code. The equation is sqrt((pow(69.1 * (lat – 44.09),2) + pow(75.1 * (-70.19 – long)*cos((lat/57.3)),2))) with the lat and long filled in for each row of course, and the values not offset. I saw your note about the offset of 3 degrees, and tried to do that, but I think I’m just misunderstanding how that should work, as doing that didn’t fix things either. Sorry if I’m missing something simple here (I clearly am). Thanks

By: Andrew

Andrew — Wed, 25 Feb 2009 14:09:36 +0000

Hi Michael, can you post the queries that you are running? I copied your locations into one of my weather sites, and I am getting the correct station back.

Remember, you have to offset your location by ~3 degrees because that radar location database is for the top-left corner of the radar coverage, and you want the center.

By: Michael Dupuis

Michael Dupuis — Wed, 25 Feb 2009 13:24:43 +0000

Is the equation to find the closest station correct? I ask because I can’t seem to get it to return the closest stations to a specified location for me. It will return a close location, but not the closest one. For example, if I use the the location for Lewiston, ME (44.09°N 70.19°W) I get BOX as the nearest station, instead of GYX, which is what I’d expect (Boston is about 120 miles from this location, Gray is only 15 miles). GYX is actually listed as the second closest. I can’t figure out what could account for this. I notice similar problems with other locations (like San Francisco, which seems to return the LA station, not the one nearest to San Francisco).