Added predefined index fuctionality, edited equations

Thank you very much for adding the functionality to directly download predefined indices through the CLI -- it has increased the efficiency of my work and minimized my data storage needs. I downloaded the EVI2 data for my region of interest and noticed that the values were higher than expected. I believe the band values were not scaled by the scale factor, which changed the relationship between the band values and the constant value of 1 in the equation: 2.5 ((b4 - b3) / (b4 + (2.4b3) + 1)). I edited the equations in order_now.py to account for a scaling factor of 10,000 where applicable. Are there any data products offered by Planet that have a scaling factor other than 10,000?

In doing so, I noticed that the TVI equation in the order_now.py file for the Triangular Vegetation Index (TVI) sourced from Broge and Leblanc was actually the equation for the Transformed Vegetation Index (TVI) developed by Deering et al (1975). I adjusted the equation to be the TVI as seen in Broge and Leblanc, and added Deering's TVI as an additional predefined index in the CLI.

Thank you again for this CLI, it is a game-changer. Please feel free to contact me if you have any questions about the suggested changes. I'd love to contribute more to this in the future.

Isabella Hinks irhinks@ncsu.edu

tyson-swetnam / porder

Added predefined index fuctionality, edited equations #48