Tuesday, May 19, 2015
Working with MODIS L1B from scratch. 1. getting the data
The Moderate Resolution Imaging Spectrometer (MODIS), onboard both Aqua and Terra platforms, is among the best instruments at the geoscientist's disposal. It not only has the possibly best calibration available in civilian platforms and a revisit time of 1/2 days, but the data is also accessible free of charge. In addition, since the Terra and Aqua platforms are designed to fly over any region at mid-morning and early afternoon, respectively, it is possible to get images from the same portion of Earth at two times of the same day. MODIS has 36 bands of varying widths spanning from visible to the thermal infrared parts of the spectrum, with ground sample sizes between 250 and 1000 m. The instrument is specially suited for regional to global applications, or for very large systems. There are several excellent MODIS products, generated using state-of-the-art algorithms written by expert scientists, which are suited for many different purposes. For many users, these products will be just fine. However, if what we need is being able to pick up individual images, at daily frequency, and not compilation over several days (as these products often are), we need to work with Level 1 images. This is the first of a handful of posts in which I describe how to work with MODIS Level 1B images from scratch. I hope it is as useful for others as it is for me!