Phenological event extraction in IDL

Question

I’m doing phenological study using threshold method in IDL. I have a twelve-band image in 2005 (format is in .tiff not ENVI format). Twelve-band means that monthly images (Jan to Dec) have been stacked in ARCGIS.

I know how to set threshold value on a single image. But I don’t know how to set threshold value on multiband image to determine the date when grown season start and end. Start of season is determined a day when NDVI value is return to threshold value in a given year.

So what I’d like to ask:

1. Can the stacked image be in .tiff format in order to import it into IDL via envi_open_data_file procedure. Or Is it required to be ENVI file?

2. What kind of procedure and function should I use to extract start and end of season using threshold method on multiband image? Because the date when start/end of season occur is different in every vegetation types. Basically I want one image showing different places are different phenological date. Is there anyone who can help me for this?

Thanks a lot

Answer 1

Please provide more information on your data and files (what kind of data exactly each pixel contains, bit depth, floating point/int, IDL version).