Tindongo ndvi 2017 to 2026

README - Tindongo NDVI dataset File name---------tindongo_ndvi_2017_2026.xlsx Short description-----------------This file contains a Sentinel-2 Normalized Difference Vegetation Index (NDVI) time series for the Tindongo location. Data source-----------Source product: Copernicus Sentinel-2 MSI surface reflectance imagery (Level-2A), used through Google Earth Engine.Recommended Google Earth Engine collection: COPERNICUS/S2_SR_HARMONIZEDOnline source link: https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S2_SR_HARMONIZEDProducer: European Union / ESA / CopernicusGoogle Earth Engine API reference: https://developers.google.com/earth-engine/reference/restWESAT platform: https://wesat.wascal.org/Source verification date for this README: 2026-09-16 Important source note---------------------The Excel workbook itself does not store the Google Earth Engine collection ID or the WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org) job configuration. COPERNICUS/S2_SR_HARMONIZED is therefore documented as the appropriate Sentinel-2 surface-reflectance collection for these indices, but the original WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org)/GEE job or extraction script should be archived to confirm the exact collection and preprocessing settings used. Location / spatial coverage---------------------------Location label used in the file name: TindongoCountry/context: Ghana / West Africa, according to the project context.Spatial extraction geometry: not stored in the Excel workbook. For full reproducibility, archive the exact Tindongo coordinates or polygon/buffer, the spatial reducer, requested pixel scale, cloud-mask settings, and WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org) job identifier or script. Variable--------Workbook column: NDVI (unitless)Variable: Normalized Difference Vegetation Index (NDVI)Unit: DimensionlessStandard Sentinel-2 formulation: NDVI = (NIR - Red) / (NIR + Red), typically using B8 (NIR) and B4 (Red).Purpose: Indicator of vegetation greenness and photosynthetic activity. Temporal frequency------------------Nominal source revisit: approximately 5 days for Sentinel-2.Frequency in this Excel file: irregular acquisition-date series, mostly 5-day intervals.Covered period: 2017-10-29 to 2026-09-12Number of records: 635 Aggregation / extraction status-------------------------------NDVI is a derived index calculated from Sentinel-2 spectral reflectance; it is not a raw Sentinel-2 band.No temporal averaging is evident in the Excel file: each row corresponds to one retained acquisition date.The workbook contains one scalar NDVI value per date, but it does not document whether that value is a point/pixel extraction or a spatial average over a Tindongo area. Do not describe it as a spatial average unless the WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org)/GEE extraction configuration confirms this. Extraction method-----------------According to the project workflow, the data were extracted through the WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org), which wraps Google Earth Engine functionality. General workflow:1. Select Sentinel-2 imagery in Google Earth Engine for the Tindongo area.2. Filter the imagery to the requested period.3. Apply the preprocessing configured in WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org)/GEE (for example cloud filtering/masking, if configured).4. Compute the requested spectral index from Sentinel-2 reflectance bands.5. Extract one index value for the Tindongo spatial target for each retained acquisition date.6. Export the resulting time series to Excel. The Excel files do not preserve the exact WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org)/GEE reducer, cloud-mask rule, pixel scale, or geometry. These settings must be retained with the original extraction job for complete reproducibility. Recommended reproducibility information to archive with this file------------------------------------------------------------------ Exact Tindongo coordinates, polygon or buffer.- Google Earth Engine collection ID actually used by the WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org) job.- Sentinel-2 bands used in the index formula.- Cloud filter and/or cloud-mask method.- Spatial reducer used (point sample, nearest pixel, mean over buffer/AOI, etc.).- Requested extraction scale and projection.- WASCAL Easy Satellite Data Access and Analysis Tool (WESAT) (https://wesat.wascal.org) job identifier or extraction script/version.- Extraction/export date and operator.- Any additional quality filters or post-processing applied after extraction. Quality and interpretation notes--------------------------------These are derived satellite spectral indices, not direct field measurements.Sentinel-2 Level-2A data represent atmospherically corrected surface reflectance. The Google Earth Engine harmonized collection has a nominal Sentinel-2 revisit interval of about 5 days, but the actual dates retained in an exported time series can be irregular because of satellite acquisition geometry, cloud screening/masking, missing observations, or extraction settings.The three Excel files contain the same 635 acquisition dates, from 2017-10-29 to 2026-09-12. Most consecutive records are 5 days apart, with some 2- or 3-day intervals and a few larger gaps. Therefore the files should be described as acquisition-date time series with approximately 5-day nominal frequency, not as daily or monthly series.There are no duplicate dates and no empty index values in the supplied workbooks. File structure--------------Workbook sheet name: Sheet1Columns:- Date: Sentinel-2 acquisition/observation date in YYYY-MM-DD format.- NDVI (unitless): extracted NDVI value for Tindongo. Prepared for------------WASCAL data preparation workflowREADME prepared on: 2026-09-16Prepared by: Dr Belko Abdoul Aziz DIALLO