Updating hurricane web maps for Ivan and Jeanne

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Tyler Mitchell
Sep. 14, 2004 11:18 PM
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URL: http://spatialguru.com/maps/apps/global/...

In an earlier weblog I outlined the process of adding a hurricane track to my MapServer web application. Due to the interest in that weblog, I thought a brief update might be worthwhile.

Since that time I've added two more hurricanes: Ivan and Jeanne. In a perfect world, these would just start showing up on my map, but since we are in the real world some effort was required - but not much!

Shortly after I posted the weblog on Hurricane Frances, I went back through the "capabilities document" for the web server that I was pulling the hurricane maps from. Lo and behold I found that there was now a layer showing Ivan's track. Then, just tonight, I looked again and found Hurricane Jeanne.

What did that mean to me? All I had to do was add a couple more pointers to these layers in my web map application and users could then see all the major hurricane activity in that part of the world.

I simply copy/pasted the layer definition for Hurrican Frances, and then changed a couple of layer names to the newer tracks. Here is an example of the syntax of the MapServer configuration:



LAYER
  GROUP jeanne
  NAME jeanne_track
  TYPE RASTER
  STATUS OFF
  CONNECTIONTYPE WMS
  CONNECTION "http://dev.gomoos.org/cgi-bin/wms_nhc?"
  METADATA
    "wms_name" "jeanne_track"
    "wms_srs" "EPSG:4326"
    "wms_server_version" "1.1.1"
    "wms_layers" "jeanne_track"
    "wms_request" "GetMap"
    "wms_format" "image/gif"
    "wms_connectiontimeout" "60"
  END
END

Wherever you see the word "jeanne" is where I had to make changes. When hurricane Amy appears out of nowhere, I'll copy/paste the layer definition and change "jeanne" to "amy" and my collection of hurricanes will continue to grow.

For those who are interested in the technology I am using here, this Global Mapping Site is running on a Pentium 4 processor, with SuSE Linux 9.1 and Apache2 web server. I'm running MapServer as a CGI application. The data sources on the site include local GeoTIFF images, ESRI shape files and remote/external images that are requested from various servers in real-time across the 'net. The graphical interface is pure HTML. I know it's ugly, but I'm looking to setup a better interface. I'm planning to implement two other interfaces: one based on the Chameleon project and another using the Open Source Internet Geo-mapping Framework (IGF). Both look promising and are based on PHP.

In short, using MapServer for my Global Map has been fun and I am really enjoying being able to provide a useful service based on completely open source tools. The only thing the map is costing me is time and a DSL connection!

To close, my sympathy goes out to those being affected by this seemingly endless barrage of storms.

Tyler Mitchell is the author of Web Mapping Illustrated - a book focused on teaching how to use popular Open Source Geospatial Toolkits. He works as the Executive Director of the Open Source Geospatial Foundation, aka OSGeo.

Tell me what you think of the global mapping site or web mapping in general. I'd love to know how you'd apply the technology if it was readily available to you.
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Showing messages 1 through 3 of 3.

a question about the webserver
2004-09-17 20:43:52 joshyx [Reply | View]

Hi Tyler. I've been working on a simple webstart Java app that will show the current hurricane. I've been able to load each layer using code like this:



        StringBuffer sb = new StringBuffer();

        sb.append("http://dev.gomoos.org/cgi-bin/wms_nhc?");

        sb.append("request=GetMap");

        sb.append("&format=image/gif");

        sb.append("&srs=EPSG:4269");

        sb.append("&version=1.1.1");

        sb.append("&layers="+layer);

        //sb.append("&bbox=-100+100+200+200");

        try {

            URL url = new URL(sb.toString());

Unfortunately this shows the entire country. How do you set the size of the bounding box? Do you have to provide some coordinates in lat/long units?

Thanks,<br/>
- Joshua

BTW, if you want to see the app: click here:
http://code.joshy.org/projects/stormdrain/StormDrain.jnlp

a question about the webserver
2004-09-17 21:24:21 Tyler Mitchell [Reply | View]
Hi Joshua, thanks for commenting. You are only a step away from satisfaction!

First, a couple tips.

The OpenGIS WMS specs can very helpful (here)

A quick read says that the bbox syntax you used is wrong (sorry :), the coordinates must be comma-separated. i.e. &bbox=-180,-90,180,90 will give a map for the whole earth. Bbox defines the geographic extents shown on the map, so you just need to hone that down a little bit.

Second tip, if you build your own URL and make some mistake, the provider will often return a message that is quite helpful. For example, I tried:
```
http://dev.gomoos.org/cgi-bin/wms_nhc?request=GetMap&format=image/gif&srs=EPSG:4269&version=1.1.1&layers=frances_track&bbox=-100+100+200+200
```
and got back an XML doc with this message:
```
Wrong number of arguments for BBOX.
```
Once I replaced with a (more?) valid coordinates and put in commas instead of +, then it works.

The only other factor that you may not be familiar with is the ability to request an image size. This is done using
```
&height
```
and
```
&width
```
and is given in pixel size.

Here's one URL I came up with for a tiny image.
```
http://dev.gomoos.org/cgi-bin/wms_nhc?request=GetMap&format=image/gif&srs=EPSG:4269&version=1.1.1&layers=land,frances_track&bbox=-120,20,0,40&width=200&height=150
```

Jeanne not Jeanine
2004-09-15 18:14:04 Tyler Mitchell [Reply | View]

Ah the beauty of bleeding-edge. Somewhere along the way, the name of one hurricane got written wrong. I received a courteous email today letting me know of the mistake and have updated this weblog (and the web service) to reflect reality.

--Tyler

Showing messages 1 through 3 of 3.

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