A not-very-portable way to generate gifs of Sentinel satellite images of an area.
When creating raster maps of an area based on satellite imagery, the specific image you use matters. As an example, the other day I was making some maps of Parque Nacional Bahía de Loreto. The area is highly seasonal, with cool, wet winters and hot, dry summers. So it makes a huge difference if you make your map with a January image...
...or one from April.
My question as a result is this: how can we effectively visualize seasonal changes in terrain using satellite imagery?
Install based on imagemagick
instructions. Make sure that
convert is available in the command line wherever you're running the
script from. Someday, I'd love to use a python wrapper for imagemagick, but
I have been persistently unable to even install them thus far. Advice would
be much appreciated.
Get data from the Copernicus Open Access Hub. You'll have to create an account, then search in a specified area. If you're looking to use this package, you'll probably want images of the same tile over time. As a tile example, the islands shown in this package are in tiles RVP and RWP, off the coast of Baja California Sur. (First rule of GIS: your area of interest always bridges multiple tiles.) Thus far, I've used Sentinel 2B, level 1C data. I don't think I've incorporated that assumption in the code, but ymmv.
I recommend just downloading the true color images (TCIs), as it's faster and that's all you need for this script. If you're already downloading the full dataset I should note that imagemagick does not seem to respect symlinks, so you'll want to either rewrite file-finding logic in the script (hit me up with a pull request!) or actually copy the TCIs to a single directory so the script can find them.
Further augmenting my desire for a usable python wrapper...command line
imagemagick as I have it installed cannot operate on JPEG 2000 images
(.jp2 extension), which means you'll need to do something to convert the
TCIs into normal JPEGs (the script looks for .jpg files). In the end, the
low-tech solution seemed to work best: open a file in Preview, save as,
change the file type to jpeg, save. YUCK.
See installation instructions on the pipenv github page
You'll want to use pipenv shell in the directory with this Pipfile and
lock file. If you're running in an OS other than OS X, and an issue
arises, you may need to relock the pipenv (pipenv lock).
The script is called animate_islands.py. Run it with, for instance:
python animate_islands.py --help
At the moment, I've embedded information about where islands in the national marine park are located, pixel-wise. If I continue development, the first thing to be added will be support for arbitrary tiles and crop frames. For now, to generate a gif like the above, use
python animate_islands.py /path/to/tci/directory coronados --destination result_file.gif
Wait a minute as it processes and makes some expensive imagemagick calls,
then check out result_file.gif. Congrats, you have a gif!