Motivation
I was poking around MetService’s publicly available data (as a tend to like doing :-P) on the weekend and stumbled across their weather radar images folder.
This folder is home to about 15,000 images spread across 5 days, that cover all the different monitored areas. I thought it might be fun / an interesting learning experience to get all of the full New Zealand weather radar images and make a time-lapse.
I was particularly interested in doing this because of the storm that hit New Zealand recently causing some widespread damage. I am currently living in Wellington as of two weeks ago which got hit hard by the storm.
Image Retrieval
The 15 thousand images all sit in the one directory – ‘http://www.metservice.com/IcePics/ob/‘.
For the purposes of an overall New Zealand weather radar time-lapse we are only interested in the images that have filenames ending with ‘ImgPlayerNZ.jpeg’. Apache has a handy feature that lets you apply pattern matching to select what files to display in the index.
P=patternlists only files matching the given pattern
The full url that just lists the files that we want is: http://www.metservice.com/IcePics/ob/?P=*ImgPlayerNZ.jpeg
Now we can use wget to automatically download all of the images based on that url. Without going in to all the wget options used, here is the command:
wget -np -nH –cut-dirs=2 -R index.html http://www.metservice.com/IcePics/ob/?P=*ImgPlayerNZ.jpeg
This matched and downloaded just under 700 images into a folder.
Building The Time-lapse
I used Picasa to build the time-lapse which makes the process very easy.
- Select the images
- Click ‘Create -> ‘Move’ -> ‘From Selection’ from the menu bar.
- Select ‘Time Lapse’ as the transition type and pick an appropriate transition speed.
- Then just render and save!
Result
The 700 images are displayed in 32 seconds (~21 fps). The time-lapse shows the storm coming in from the west and covering the country. It is interesting to watch the Wellington area of the North Island near the end of the storm. There is a visible circular motion going on.
The result can be viewed on youtube.
