Hierarchical Data Format (HDF) is chosen for storing both annotated image metadata and binary image data of ICEYE products.
In order to simplify access product annotation, for e.g., indexing purposes, the key information about the product is also gathered in the auxiliary XML file.
ICEYE Basic Image products can be differentiated into geo-referenced single look complex (SLC) and ground range detected (GRD) scenes. SLC products preserve phase information and are sampled at the natural pixel spacing while GRD products store the detected amplitude and are multi-looked to reduce the speckle impact.
SLC are basic single look products of the focused SAR signal. Scenes are stored in the satellite image acquisition geometry in the slant range by azimuth imaging plane in zero-Doppler SAR coordinates. The pixels are spaced equidistant in azimuth (according to the inverse of the pulse repetition frequency) and in slant range (according to the range sampling frequency). Each image pixel is represented by a complex magnitude value (with in-phase I and quadrature Q components) and therefore, contains both amplitude and phase information. Each image pixel is processed to zero Doppler coordinates in range direction, i.e. perpendicular to the flight track.
GRD products represent focused SAR data that has been detected, multi-looked processed and projected to the ground range using an Earth ellipsoid model. The image coordinates are oriented along the flight direction and along the ground range. The pixel spacing is equidistant in azimuth and in ground range. Ground range coordinates are the slant range coordinates projected onto the ellipsoid of the Earth. For the slant to ground range projection the WGS84 ellipsoid and a scene-averaged value of terrain height is used, annotated in the metadata. Pixel values represent detected magnitude