Associated metadata describing inputs to the correction is included in a GeoTIFF ImageDescription metadata header as a JSON encoded string. By using Python, you can extract the inputs from a PlanetScope or SkySat image atmospherically corrected surface reflectance product (analityc_sr, ortho_analytic_sr).
filename = rasterio.open('20210913_211131_ssc15_u0001_analytic_SR.tif') #item ID: PlanetScope or SkySat
tags = filename.tags()['TIFFTAG_IMAGEDESCRIPTION']
jtags = json.loads(tags)
atm_inputs = jtags['atmospheric_correction']
print ("atmospheric correction", json.dumps(atm_inputs, indent=4))
For more information about Planet Surface Reflectance please check this document:
I have some SkySat Collect product pansharpened without any reflectance coefficients.
I don't see any documentation about this, so I don't even know what is the units of these products.
Here is the content of the product:
And the tags:
Do you know something about this ?
Thank you for your comment. The reflectance coefficients for SkySat are available for products that have been transformed to Top of Atmosphere radiance. (ortho_analytic, ortho_panchromatic). For 20201223_220311_ssc13_u0002, the reflectance coefficients are:
Panchromatic: "reflectance_coefficients": [2.1774764118470272e-05]
Analytic radiance (TOAR): "reflectance_coefficients": [1.7138619391877836e-05, 1.8910223621257227e-05, 2.17299756251008e-05, 3.105477468010073e-05]
The pansharpened data does not have meaningful radiometric units (They are uncalibrated). You can find more info about SkySat products at https://developers.planet.com/docs/data/skysat/
I hope you find this helpful. If we can be of any further assistance, please let us know.
Ok, thanks for for quick response :)
So, if I understand correctly, it makes no sense to try to get pansharpen data in reflectance, I should leave them in DN ?
Thank you for reaching out. For Planet images that's correct. Pansharpened products are designed for multispectral applications which require highest available resolution and accurate geolocation and cartographic projection. If you need reflectance pixel values in a SkySat collect, I would recommend to download the surface reflectance product.
If you have any more questions, please let us know. :)
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