EARTH IMAGERY SELECTION AND COMPARISON
Yenra | October 11, 2026
Guide: https://yenra.com/earth-imaging/
Search: https://earthexplorer.usgs.gov/
Access guidance: https://www.usgs.gov/landsat-missions/landsat-data-access
Scaling: https://www.usgs.gov/faqs/how-do-i-use-a-scale-factor-landsat-level-2-science-products

Purpose: plan a small image comparison, record each source, and separate
an observed difference from an explanation. Fill both image records.

Question:
Area of interest / boundary file:
Smallest feature needed:
Acceptable acquisition dates and seasons:
Required bands or derived measurement:
License and attribution requirements:

IMAGE A / IMAGE B (copy this block for each)
Provider and source URL:
Product identifier:
Sensor, collection, version, and processing level:
Acquisition date/time (not publication date):
Spatial sampling / units / native grid:
Bands and band-to-display assignments:
Reference system and footprint:
Cloud, shadow, snow, fill, and other exclusions over the actual site:
Quality files and flags used:
Downloaded metadata and original data paths:

COMPARISON SETTINGS
Common clear comparison area:
Grid alignment and stable features checked:
Any reprojection / resampling method:
Scaling and offsets applied, and whether software had applied them already:
Display stretch for each image:
Boundary ambiguity / classification method / independent checks:

TEACHING EXERCISE -- invented reservoir comparison, no measured result
The second image shows a larger exposed shoreline in the clear area.
Observation: visible water extent appears smaller on the second date.
Evidence still needed to explain it: additional dates, water-level records,
rainfall, reservoir management information, and checks for image artifacts.
One image pair alone does not isolate a long-term climate trend.

SCALING CHECK -- specific to Landsat Collection 2 Level-2 surface reflectance
For an invented valid stored pixel value of 18639:
Reflectance = 18639 x 0.0000275 - 0.2 = 0.3125725.
Apply appropriate quality/fill masks. Confirm product-specific scaling and
avoid double conversion if software has already scaled the data.

FINAL RECORD
Observed difference:
Proposed explanation:
Alternative explanations / unresolved limitations:
Independent supporting evidence:
Reviewer and retrieval date: