Planet Imagery and Color Correction

Processing applied to visual products

Our visual products (not analytic, etc.) are processed to present the imagery as natural color, optimized as seen by the human eye. This process consists of three steps:

  • Nominalization - Sun angle correction, to account for differences in latitude and time of acquisition. This makes the imagery appear to look like it was acquired at the same sun angle by converting the exposure time to the nominal time (noon).
  • Unsharp mask (sharpening filter) applied before the warp process.
  • Custom color curve applied post warping.

Processing for analytic products

No automatic color processing is applied to our analytic products. We scale reflectance values by 10,000 to reduce quantization error, where 10,000 represents a reflectance of 1. For visual scaling, you will usually want to clip well before a reflectance of 1.0.

As a start, a linear scaling of 0-3000 for RGB bands and 0-5000 for false color infrared works well. For a proper visual display, you'll need to use a non-linear scaling. Our eyes do not perceive intensity linearly, and making a good visual curve is very much an art form. We recommend creating a single curve (or formula) and then apply it to all your tiles for a consistent appearance.

Read more about the procedure on creating a color curve.

Preview in Planet Explorer

For our preview in Planet Explorer, PlanetScope Top of Atmosphere Reflectance is used and then has a consistent, non-linear color curve applied to match the data to the human visual system. It’s designed to provide consistency no matter where or when the data were collected, so all of the images are comparable with one another. They are not optimized for maximum contrast in each image, or for extreme lighting conditions (particularly snow- or ice-covered areas of the Arctic and Antarctica).

 

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