MODAPS PCR 17-021
| PCR Number | 17-021 |
|---|---|
| Date | 2017-08-18 |
| Initiator | Kamel Didan |
| Abstract | PGE25 v6.0.34, PGE35 v6.0.23 code change: - To handle end of the year and days from next cycle - Evaluate alternative pixels as opposed to the MVC (dictated by the 500m selection) - Apply a thresholds test based on NDVI and RED/NIR ratios - Change the logic for composite to bin optimize NDVI under 30VZA for good quality data - Backup EVI equation updated to use the EVI2 |
| Problem Statement | The 250M resolution VI product (MxD13Q1) contained spikes of large VI values and no data pixels. The 250m and 500m resolution VI products (MxD13A1 and MxD13Q1) generated for the last 16-day cycle of the year contained data gaps. |
| Description of Change | Code was fixed to handle end of the year and days from next cycle. To fix the spikes and no data in the 250m/500m product, evaluate alternative pixels as opposed to the MVC (dictated by the 500m selection) and apply a thresholds test based on NDVI and RED/NIR ratios. Additional change to improve the product quality include logic for composited changed to bin optimize NDVI under 30VZA for good quality data and backup EVI equation updated to use the EVI2. |
| Products Affected | MOD13A1, MOD13Q1, MOD13A2, MYD13A1, MYD13Q1, MYD13A2 |
| Software Affected | PGE25 v6.0.34, PGE35 v6.0.23 |
| Processing String to Receive the Change | Terra and Aqua Forward Processing. Terra and Aqua Reprocessing. |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Ran science test generating global product from a 16-day period of Aqua and Terra. |
| Justification | With these code changes, the product from the last cycle of the year will generate good quality products with no data gap. 250m and 500m products are less noisy with retrievals that are more homogeneous. With these changes, as much as 20% of the retrievals globally could change from the current operational version with overall increase in NDVI and EVI. There is less cloud contamination in the products. A re-reprocessing of the 250m/500m and 1km products is recommended to remove any possible temporal inconsistency from use of this revised version in the C6 operational processing. |
| Effective Date for Implementation of Change | Completed. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 08/18/2017. Michael King approved 08/28/2017. Gang Ye implemented 08/29/2017. |
