# 6. Radiometric resolution and correction #### Radiometric resolution The radiometric resolution refers to how much information is contained within the image – effectively what the bit-depth is. ​ An image may be 8 bit, 16 bit or 32 bit. ​ #### Radiometric correction The radiometric correction is the process of correcting the colour and brightness of the image to take out spectral distortion. ​ When light passes through the atmosphere some wavelengths are absorbed or reflected more than others. ​ There are two main types of correction for this: ​ 1. Top Of Atmosphere (TOA) correction; based on the known position and angle of the satellite and the sensor 2. Full Atmospheric Correction (FAC); based on knowing the composition of the atmosphere at the time of the image.​ ​Getting a true FAC is usually difficult in Antarctica, as we rarely know the composition of the atmosphere. But luckily, the levels of aerosols and other pollutants are small, so usually a TOC correction will suffice. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://guides.geospatial.bas.ac.uk/10-things-to-know-about-vhr-satellite-data/6.-radiometric-resolution-and-correction.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.