I am having a hard time to figure out what this information refers to. It is stated at the product description of Terra MODIS MOD11A1 product (Wan et al.,2015). (from https://lpdaac.usgs.gov/products/mod11a1v006/)

(It is also mentioned at the dataset page of Earth Engine Data Catalog at https://developers.google.com/earth-engine/datasets/catalog/MODIS_006_MOD11A1)

"Above 30 degrees latitude, some pixels may have multiple observations where the criteria for clear-sky are met. When this occurs, the pixel value is a result of the average of all qualifying observations."

From Version 5, temporal averaging was removed from the MOD11A1 products, and they have now LST data by instantaneous observations. I am saying this based on;

For daily MOD11A1 product, in the MODIS LST Products User's Guide of Version 4 products (by Wan Z. (2006) ) there was this information " As latitude increases beyond 30 degrees, the LST value at some grids in the MOD11A1 product may be the average value of LSTs retrieved from multiple MODIS observations in clear-sky conditions in day or night. If LST values from single clear-sky MODIS observations are required for all grids, the MOD11_L2 LST product and MODIS geolation product (MOD03) should be used instead."

Which was changed into "As latitude increases beyond 30 degrees, there may be multiple MODIS observations in clear-sky conditions. In V5 MOD11A1 product, LST values at all grids are from single clear-sky MODIS observations by selecting LSTs in MOD11_L2 files at smaller viewing zenith angles or the LSTs at larger zenith angles but their values being larger by at least 2K" in the Collection-5 MODIS Land Surface Temperature Products Users' Guide (Wan Z., (September 2006).

In this context, I would like to ask if anybody could help with the above information? What type of averaging is being referred to?

1 Answer 1


Based on the satellite orbit and sensor viewing characteristics, there are can be overlapping observations at high-latitudes within a day. This video is a nice animation of the Aqua satellite swath: https://youtu.be/d4QLDlAumOc?t=24. Notice how some areas get imaged twice in the north.

That is what "the pixel value is a result of the average of all qualifying observations." is referencing. So, if a location is observed multiple times which meets the quality assurance criteria (no clouds, no sensor saturation, etc.) then the level 3 data (MOD11A1V006) is the average of those observations.

Hopefully this sheds some light into how the dataset is generated.

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