MODIS Data Inconsistencies with GEE

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cevre
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Joined: Fri Dec 20, 2024 1:50 am America/New_York
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MODIS Data Inconsistencies with GEE

by cevre » Fri Dec 20, 2024 2:04 am America/New_York

I can export MODIS data using the geemap library in Python or from Google Earth Engine (both option results are the same). However, I am comparing the data downloaded via GEE with the data downloaded directly from the source and noticing inconsistencies in pixel values when inspecting the data in ArcGIS.

Data source: https://lpdaac.usgs.gov/products/mod17a3hgfv061/

The following code exports the Net Primary Productivity (NPP) data for Turkey in 2022 using Google Earth Engine (GEE):

// Load the NPP data for 2022 from MODIS
var npp2022 = ee.Image('MODIS/061/MYD17A3HGF/2022_01_01')
.select('Npp') // Select the 'Npp' band
.multiply(0.0001) // Apply the scale factor
.rename('NPP_2022'); // Rename the band for clarity

// Define the geometry for Turkey using a country boundaries dataset
var turkey = ee.FeatureCollection('USDOS/LSIB_SIMPLE/2017')
.filter(ee.Filter.eq('country_na', 'Turkey')); // Filter for Turkey

// Clip the NPP image to the geometry of Turkey
var nppTurkey = npp2022.clip(turkey);

// Export the NPP image for Turkey to Google Drive
Export.image.toDrive({
image: nppTurkey, // Image to export
description: 'NPP_2022_Turkey_Map', // Description of the exported file
scale: 500, // Spatial resolution in meters
crs: 'EPSG:4326', // Coordinate reference system
region: turkey, // Region of interest
maxPixels: 1e13 // Maximum number of pixels allowed
});
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LP DAAC - dgolon
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Re: MODIS Data Inconsistencies with GEE

by LP DAAC - dgolon » Fri Dec 27, 2024 1:28 pm America/New_York

Hi @cevre Thanks for writing in. The LP DAAC is the official source of the MYD17A3HGF data. However, once the data leaves our archive and is re-hosted by another source, we are unable to speak to their copy of the data. We recommend reaching out to the GEE team directly if you have any questions about MODIS data accessed through GEE: https://developers.google.com/earth-engine/help
Subscribe to the LP DAAC listserv by sending a blank email to lpdaac-join@lists.nasa.gov.

Sign up for the Landsat listserv to receive the most up to date information about Landsat data: https://public.govdelivery.com/accounts/USDOIGS/subscriber/new#tab1.

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