Update README.md

README.md

@@ -2,18 +2,18 @@
 license: apache-2.0
 ---
 
-NAIP-S2 is a super-resolution dataset for remote sensing consisting of paired NAIP and Sentinel-2 images in the continental US.
+S2-NAIP is a super-resolution dataset for remote sensing consisting of paired NAIP and Sentinel-2 images in the continental US.
 
 Data is divided into tiles.
 Each tile spans 512x512 pixels at 1.25 m/pixel in a UTM projection.
 At each tile, the following data is available:
 
-- NAIP: an image from 2019-2021 at 1.25 m/pixel (512x512).
-- Sentinel-2: between 16 and 32 images captured within a few months of the NAIP image at 10 m/pixel (64x64).
-- Sentinel-1: 4 images captured in the same year as the NAIP image at 10 m/pixel (64x64).
-- Landsat: 4 images captured in the same year as the NAIP image at 10 m/pixel (64x64).
-- OpenStreetMap: a GeoJSON containing buildings, roads, and 30 other categories. It uses pixel coordinates relative to the 512x512 NAIP image.
-- WorldCover: the 2021 land cover image at 10 m/pixel (64x64).
+- [National Agriculture Imagery Program (NAIP)](https://www.usgs.gov/centers/eros/science/usgs-eros-archive-aerial-photography-national-agriculture-imagery-program-naip): an image from 2019-2021 at 1.25 m/pixel (512x512).
+- [Sentinel-2 (L1C)](https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-2): between 16 and 32 images captured within a few months of the NAIP image at 10 m/pixel (64x64).
+- [Sentinel-1](https://sentinels.copernicus.eu/web/sentinel/missions/sentinel-1): between 2 and 8 images captured within a few months of the NAIP image at 10 m/pixel (64x64).
+- [Landsat-8/9](https://www.usgs.gov/landsat-missions/landsat-8): 4 images captured in the same year as the NAIP image at 10 m/pixel (64x64).
+- [OpenStreetMap](https://www.openstreetmap.org): a GeoJSON containing buildings, roads, and 30 other categories. It uses pixel coordinates relative to the 512x512 NAIP image.
+- [WorldCover](https://worldcover2021.esa.int/): the 2021 land cover image at 10 m/pixel (64x64).
 
 
 Structure
@@ -21,7 +21,7 @@ Structure
 
 Once extracted, the dataset contains the different data types in different folders.
 Each folder contains files named by a tile ID, which consists of the UTM projection, column, and row.
-The column and row are based on tiles that are 512x512 pixels with pixel coordinates at 1.25 m/pixel, e.g. `32612_960_-6049.png` spans (614400, -3871360) to (615040, -3870720) in projection units.
+The column and row are based on tiles that are 512x512 pixels with pixel coordinates at 1.25 m/pixel, e.g. `32612_960_-6049.png` spans (614400, -3871360) to (615040, -3870720) in EPSG:32612 projection units.
 
 Here is an example of NAIP data:
 
@@ -44,5 +44,46 @@ sentinel2/
     ...
 ```
 
-Note that the Sentinel-2 images are GeoTIFFs so they contain georeference metadata.
-Furthermore, the 10 m/pixel (`_8.tif`), 20 m/pixel (`_16.tif`), and 60 m/pixel (`_32.tif`) bands are stored separately.
+The Sentinel-2, Sentinel-1, and Landsat images are GeoTIFFS so they contain georeference metadata.
+Other data does not have georeference metadata, but data at each tile is aligned, so the georeference metadata from the above images is applicable to the other data as well with only a resolution shift.
+
+
+Sentinel-2
+----------
+
+The 10 m/pixel (`_8.tif`), 20 m/pixel (`_16.tif`), and 60 m/pixel (`_32.tif`) bands are stored separately.
+Pixel values are the L1C 16-bit values.
+
+The band order is as follows:
+- _8.tif (64x64): B02, B03, B04, B08
+- _16.tif (32x32): B05, B06, B07, B8A, B11, B12
+- _32.tif (16x16): B01, B09, B10
+
+The GeoTIFFs contain multiple images concatenated along the channel axis.
+The CSV shows the original Sentinel-2 scene ID of each image.
+
+
+Sentinel-1
+----------
+
+The Sentinel-1 bands are 10 m/pixel and ordered VV then VH.
+
+Only IW VV+VH scenes are used.
+
+The pixel values are 32-bit floating point values representing decibels 10*log10(x).
+We obtain the radiometric-calibrated and terrain-corrected images from Google Earth Engine so see
+https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S1_GRD for details.
+
+The GeoTIFFs contain multiple images concatenated along the channel axis.
+The CSV shows the original Sentinel-1 scene ID of each image.
+
+
+NAIP
+----
+
+The NAIP image is 512x512 with four 8-bit bands: R, G, B, IR.
+
+It is encoded as PNG but the IR is alpha mask so cannot be visualized correctly in image viewer without removing the alpha mask.
+
+There are two NAIP images available, one under "naip" (2019-2022) and one under "oldnaip" (2015-2018).
+The CSV shows the original NAIP scene ID of each image.