phpweather-devel

Generating weather maps

[Jonas K. <me...@j0...>]

Hello there,

as Martin posted some days ago, I developed a little weather map with
the help of phpWeather(see: http://www.j0nes.de/wetter/ - be patient,
a lot of METARs have to be fetched *g* - but weather.noaa.gov seems to
be down, so no data for now).
Together with the idea of having lat/long-data for every station in
the database, it would be possible to generate those maps for every
country on the fly.

I just checked how to figure out the positions on the map with
latitude and longitude, and this works quite well - assuming that we
have the exact location and range of the map.
A problem might be to find suitable map data for each country.

But... I found a nice Sourceforge project called GeoClass. It has some
very nice features such as converting lat/long-positions to
x/y-positions, getting position data from DB and storing them in a
GeoObject or, even better, generating maps out of a .e00-textfile.
You can find this project here: http://sourceforge.net/projects/geoclassphp/
I will have to take a closer look at this project. With the help of
those classes weather map generation might get a lot easier.

Cu
Jonas Kaufmann




  

Re: Generating weather maps

[Phil P. <phi...@sw...>]

Very nice.

A simple workaround for the "it's not fast" issue would be to schedule 
(eg cron) the map generation rather than recalculating it for each Page 
View.

I believe most METARS are only released on an hourly schedule, though I 
think I recall reading somewhere that some locations generate 
half-hourly ones.

One simple thing I'd always thought would look nice was a worldmap with 
every METAR station pinpointed. ImageMap to select a country, then show 
(for example) your country weather map, and image-map to get detailed 
METAR report.

Phil P

Jonas Kaufmann wrote:
> Hello there,
> 
> as Martin posted some days ago, I developed a little weather map with
> the help of phpWeather(see: http://www.j0nes.de/wetter/ - be patient,
> a lot of METARs have to be fetched *g* - but weather.noaa.gov seems to
> be down, so no data for now).
> Together with the idea of having lat/long-data for every station in
> the database, it would be possible to generate those maps for every
> country on the fly.
> 
> I just checked how to figure out the positions on the map with
> latitude and longitude, and this works quite well - assuming that we
> have the exact location and range of the map.
> A problem might be to find suitable map data for each country.
> 
> But... I found a nice Sourceforge project called GeoClass. It has some
> very nice features such as converting lat/long-positions to
> x/y-positions, getting position data from DB and storing them in a
> GeoObject or, even better, generating maps out of a .e00-textfile.
> You can find this project here: http://sourceforge.net/projects/geoclassphp/
> I will have to take a closer look at this project. With the help of
> those classes weather map generation might get a lot easier.
> 
> Cu
> Jonas Kaufmann
> 
> 
> 
> 
>   
> 
> 
> 
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Re[2]: Generating weather maps

[Jonas K. <me...@j0...>]

Hello,

> A simple workaround for the "it's not fast" issue would be to schedule
> (eg cron) the map generation rather than recalculating it for each Page
> View.

Yes, this would be really useful. I already use a simple sort of
caching, that is generating the map on the first request and storing
it. Every other request in the next half hour gets the cached version
of the map. Image generation itself is quite fast, getting all METARs
takes a lot of time. So perhaps scheduling the METAR fetch might be
sufficient.

Another problem is that I have to fetch the METARs twice - one time in
the map-generating script, the other time in the HTML-page to display
the onMouseOver-Information for every station. Even with the built-in
caching of phpWeather, I still have to query my database two times.
Has anybody got an Idea how to solve this?

> One simple thing I'd always thought would look nice was a worldmap with
> every METAR station pinpointed. ImageMap to select a country, then show
> (for example) your country weather map, and image-map to get detailed
> METAR report.

Nice idea. World map generation can also be done with the script I
use. We also need positions for every country, so it would
even be possible to generate the ImageMap to select a country
dynamically.


Cu Jonas

Re: Generating weather maps

[Phil P. <phi...@sw...>]

Jonas Kaufmann wrote:

>>A simple workaround for the "it's not fast" issue would be to schedule
>>(eg cron) the map generation rather than recalculating it for each Page
>>View.
> 
> 
> Yes, this would be really useful. I already use a simple sort of
> caching, that is generating the map on the first request and storing
> it. Every other request in the next half hour gets the cached version
> of the map. Image generation itself is quite fast, getting all METARs
> takes a lot of time. So perhaps scheduling the METAR fetch might be
> sufficient.

I use the PHP/PEAR Cache::Lite module to do my caching, nice and fast 
and pretty functional.

> Another problem is that I have to fetch the METARs twice - one time in
> the map-generating script, the other time in the HTML-page to display
> the onMouseOver-Information for every station. Even with the built-in
> caching of phpWeather, I still have to query my database two times.
> Has anybody got an Idea how to solve this?

Have the HTML page do the query, and send the data in the URL to the map 
generate script. Caching this is *trivial* with the Cache::Lite module.

	/* near the start of your script */
	require 'Cache/Lite/Output.php';
	$cacheOptions = array(
	    'cacheDir' => "/full/path/to/cache/directory",		//NB cacheDir needs 
g+wx permissions
	);
	$Cache_Lite = new Cache_Lite_Output($cacheOptions);	
		
	/* when you need to cache something */		
	$cacheID = 
substr($_SERVER["REQUEST_URI"],0,strcspn($_SERVER["REQUEST_URI"],'#'));
	$Cache_Lite->setLifeTime(30*60); // cache LifeTime is in Seconds
	$cacheGroup = "weatherMap" ; // :-) just pick a friendly group name
	
	if(! ($Cache_Lite->start($cacheID,$cacheGroup))) {
	
		/* code here to generate page/image when not cached or cache is invalid */
	
		$Cache_Lite->end();
	}

$cacheID is the unique identifier of what you're caching
$cacheGroup is a name to group multiple cacheIDs (eg you can "flush 
ThisGroup from the cache", as opposed to flushing TheWholeCache)

>>One simple thing I'd always thought would look nice was a worldmap with
>>every METAR station pinpointed. ImageMap to select a country, then show
>>(for example) your country weather map, and image-map to get detailed
>>METAR report.
> 
> 
> Nice idea. World map generation can also be done with the script I
> use. We also need positions for every country, so it would
> even be possible to generate the ImageMap to select a country
> dynamically.

You mean simply Lat/Long for each station? I've been looking in to that, 
(checkout my earlier posts in the archives) we can get the data easily 
(I just need to get my act together and clean it up and thunk it into 
the METAR station table)

Enjoy,
Phil P

Re[2]: Generating weather maps

[Jonas K. <me...@j0...>]

Hello,

> Have the HTML page do the query, and send the data in the URL to the map
> generate script. Caching this is *trivial* with the Cache::Lite module.
> [snip]

Thanks, I will try this.

>>>One simple thing I'd always thought would look nice was a worldmap with
>>>every METAR station pinpointed. ImageMap to select a country, then show
>>>(for example) your country weather map, and image-map to get detailed
>>>METAR report.
>> Nice idea. World map generation can also be done with the script I
>> use. We also need positions for every country, so it would
>> even be possible to generate the ImageMap to select a country
>> dynamically.
> You mean simply Lat/Long for each station? I've been looking in to that,
> (checkout my earlier posts in the archives) we can get the data easily
> (I just need to get my act together and clean it up and thunk it into
> the METAR station table)

No, we also need the positions of the upper left corner and the lower
right corner of the map in addition to the lat/long-data for each
station. Perhaps we could create a new table pw_countries (cc, country,
min_lat, max_lat,  min_long, max_long) to store this information.
pw_stations could then be reduced to pw_stations(icao, cc). I don't know
whether phpWeather uses the country field from pw_stations.

Cu Jonas

Re: Generating weather maps

[Jonas K. <me...@j0...>]

Hello,

I updated my approach to generate weather maps for every country with
phpWeather. You can see the current version at
http://www.j0nes.de/wetter/. Currently I included maps for Denmark,
France, Germany and Spain, but other maps can also be integrated.

I found a very useful class named Geoclass at
http://sourceforge.net/projects/geoclassphp/. Geoclass can draw maps
out of .e00 textfiles (which are freely available for almost every
country at http://www.maproom.psu.edu/dcw/) and also does the
transformation from latitude/longitude values to x/y-positions on the
map.

A drawback is that I need several values for every map that you have
to figure out first (try and error), for example the range in
latitude/longitude for this country or the size of the map in pixels
and thus the width-to-height-ratio.

What about the latitude/longitude values for all weather stations?
Phil, browsing the archive I found postings that you had an idea
how to put those values in the pw_stations table. Did you advance in
this?

Cu
Jonas Kaufmann