# Difference between revisions of "IKONOS"

IKONOS is a commercial earth observation satellite. Details about the sensor in The IKONOS satellite collects high-quality satellite imagery for map creation, change detection, imagery analysis and more.

## Pre-Processing Overview

Tyipically, multispectral data are converted into Reflectance before they are subjected in multispectral analysis techniques (image interpretation, band arithmetic, vegetation indices, matrix transformations, etc.). As with remotely sensed data acquired by other sensors, IKONOS raw image digital numbers (DNs) can be converted to physical quantities such as at-sensor Radiance or Reflectance. The latter can be differentiated in Top of Atmosphere Reflectance (ToAR) which does not account for atmospheric effects (absorption or scattering) and in Top of Canopy Reflectance (ToCR) which introduces a "correction" for atmospheric effects.

Converting to Top of Atmosphere Reflectance, also referred to as Planetary Reflectance, can be done by using the following equation:

$\displaystyle \rho_p = \pi * L\lambda * d^2 / ESUN\lambda * cos(θ_S)$

where:

• ${\displaystyle \rho }$ - Unitless Planetary Reflectance
• ${\displaystyle \pi }$ - mathematical constant (3.14159265358)
• ${\displaystyle L\lambda }$ spectral Radiance at the sensor's aperture, from equation... ToADD
• ${\displaystyle d}$ - Earth-Sun distance in astronomical units, interpolated values
• ${\displaystyle Esun}$ - Mean solar exoatmospheric irradiance(s) (W/m2/μm), interpolated values
• $\displaystyle cos(θ_s)$ - Solar zenith angle, from the image acquisition's metadata