GRD
Ground Range Detected amplitude image data product represents focused SAR data that have been detected & projected to the ground plane using an Earth Ellipsoid model. The pixels of SAR amplitude images only contain amplitude values. GRD products are multi-looked for the reduction of speckle-effect. Ground Range coordinates are the slant range coordinates projected onto the Earth ellipsoid. For thus projection the WGS84 referenced ellipsoid is used an averaged fixed value of terrain height is used. This is what makes the ellipsoid surface closer to the true ground surface.
ICEYE packages the GRD amplitude images onto the Cloud Optimized GeoTIFF (COG) format which is supported by most image viewing software, GIS apps and data processing tools and libraries.
Pixel values depict a scaled amplitude. The finished product has approximately circular spatial resolution and square pixel spacing. There is also an incidence angle dependence in range, calculated using the ellipsoidal Earth model has been applied to deem the conversion of radar brightness to backscatter intensity feasible.
GRD products have several advantages, firstly they are laid out in the natural SAR orientation which is a requirement for geolocation and secondly their pixels do not have interpolation artifacts of map projection images. Basically this product is the form of a SAR Amplitude image that retains the SAR data from the raw product. Pixels are depicted in the natural range-azimuth form that is ideal for shadows-down interpretation, that is free of map-projection-induced artifact and facilitates interpretation of topography and elevated features.
For users requiring geocoded imagery with minimal interpolation artifacts, ICEYE amplitude image products are tagged with ground control points (GCP) and rapid positioning capability polynomial coefficients (RCP's). These allow precise geospatial exploitation using freely available tools such as QGIS or GDAL.
ICEYE provides GRD that is:
- Projected to the ground surface using Earth ellipsoid model
- May be multi-looked for the reduction of speckle noise
- Produced in the natural range-azimuth sensor orientation
- Packaged into the GeoTIFF file format with metadata included
- Free of interpolation artifacts of the map projection images
SLC
SLC (Single Look Complex) images are considered to have the highest fidelity of all SAR data because they are the closest to the original raw data collected by the radar. SLC retains all the original sensor measurements and are free from interpolation artifacts or projection issues. This data only has a single look meaning that they retain full resolution in azimuth and range. It should be noted that in several instances the impulse response function, the shape of a single, isolated radar-bright object in the product, is asymmetrical with range resolution being bigger (coarser) than azimuth resolution.
The satellite image acquisition geometry, the slant plane, is where scenes are stored. The coordinate system of the image is centered on the zero-Doppler SAR coordinates and data is arranged in the slant-range-by-azimuth imaging plane. The pixels are spaced equal distance in slant range based on the range sampling frequency and in azimuth in accordance to the inverse of the pulse repetition frequency.
Single Look Complex images are the most valuable source for SAR image analysis, complex data has inherently been packaged in scientific or military intel-formats that were difficult to use without any expertise or specialized software. ICEYE for the optimization of thus issue has been packaging its data in the international Cloud Optimized GeoTIFF (COG) format enabling user-friendly ingestion and manipulation in most GIS tools, libraries and image readers. The phase & amplitude data are formatted in 2 different GeoTIFF files just like how bands are used for multispectral images. The phase band is provided for further processing and by specialized tools while the amplitude band is ready to view.
The SLC products given are at full resolution, enabling access to users of the full resolution, the reduced-speckle and pixel-aggregated views which are produced instantly due to different levels of multi-looking when zooming in and out. As mentioned above, the SAR data inside the format is stored in the slant plane, the metadata contains RPC values that enables GIS tools to perform automatic ground projection, so they are ready to be used as part of analysis and exploitation workflows. It should be noted that Orthorectification using a Digital Elevation Model (DEM) is always recommended for precise geospatial comparison and analysis. Metadata is stored with the GeoJSON format, which is a geocoded metadata format supported by many GIS tools.
ICEYE provides SLC data:
- Excellent fidelity, full resolution in azimuth and range
- Free from interpolation artifacts or projection issues
- Packaged into the GeoTIFF file format with metadata included
- Excellent for automated processing and advanced exploitation
CSI
CSI stands for Colorized Sub-Aperture Image and it's made though the assignment of distinct colors to backscatter signals received from several sub-apertures, which are integrated into a composite color image. Man-made objects that have flat surfaces or sharp angles usually produce preferential scattering orientations that makes their appearance highlighted as a dominant color in the CSI image.
On the other hand, natural objects that have a uniformed scatter in all directions do not depict preferential scattering geometries and they appear as gray tones in the CSI product. For objects that are partially obscured by vegetation or tree canopies can be highlighted in dominant colors with the condition that a subset of sub-apertures captures strong backscatter returns.
The above provides enhancement of the effectiveness of the CSI image to identify objects that in other cases would remain hidden. This unique capability is especially valuable in search, monitoring & surveillance operations.
Lastly, the CSI products are only produced for the Dwell, Dwell Fine and Dwell Precise imaging modes due to the long total illumination of 25 seconds they provide. With the division of the total collection into 13 sub-apertures results in 13 sub-apertures with illumination periods of around 1.9 seconds each. The CSI format uses a GeoTIFF container so the image can be viewed by any geospatial image viewer. The exact time, color, duration and satellite location is provided as metadata in the CSI GeoTIFF for each sub-aperture.
ICEYE provides CSI data that is:
- Packaged as a GeoTIFF with all metadata included
- Excellent for detecting vehicles and man-made structures
- Suitable for detecting moving objects.
VID
SAR VIdeo (VID) has similarities with the CSI product mentioned in which the acquired SAR data is first divided with multiple sub-apertures. In the case of SAR Video each discrete sub-aperture image is used as frame to create a short video clip. It's worth mentioning that all Dwell imaging modes (Dwell, Dwell Fine and Dwell Precise) generate 25-second videos that are created by 25 individual frames.
The usefulness of VID product is found in applications for which the motion of moving objects, such as vessels and land vehicles, is to be analyze. Through the analysis and inspection of a video, there is possibility to infer the general direction and speed of objects in motion. SAR Video has also been deemed effective for detection of hidden objects in forested areas along with man-made objects as these tend to give bright reflections revealed as glints when playing a video.
The formats of the VID products are MPEG4 and GIF. In addition, a file in GeoTIFF format is produced where each of the video frames is available as a separate band to facilitate frame by frame analysis in GIS environment. This enables the user to track and measure the changes and moving objects between the frames by having the ability to analyze the different bands of each frame while metadata for each image is also available in the GeoTIFF.
ICEYE provides VID that is:
- Packaged in MPEG4 and GIF file formats, a GeoTIFF is also provided with each frame as a separate band
- Metadata stored in the GeoTIFF format
- Excellent for detecting moving objects
- Suitable for detecting man-made structures
Quicklook
The Quicklook product is an image preview of a higher resolution GRD image and it is available for all imaging modes and is provided in PNG format. These are very user-friendly, as they do not require a specialized software for viewing, any basic image viewer will do, along with document editing tools and raster graphics editing software.
ICEYE provides quicklook that is:
- Encoded in the PNG file format with metadata included
- Compatible with most documentation , presentation and publishing software
- Exploitable without GIS software
- Useful for first-time phase analysis
Sensor Independent Complex Data (SICD)
The Sensor Independent Complex Data (SICD) removes any sensor-specific parameters. SICD product has the same format irrespective of processing algorithm or the strategy of the collection. In principle any algorithm that uses SICD will work on SAR imagery from SAR vendor. It is worthy to note that the SICD developed by the US National Geospatial Intelligence Agency (NGA) and it is stored in the National Imagery Transmission Format (NITF) container.
Sensor Independent Derived Data (SIDD)
The Sensor Independent Derived Data stores SAR derived image products & associated metadata that is grouped around common tasks for typical user workflows. The SIDD and SICD standard are supposed to work alongside each other, defining format standards for SAR image processing.
SIDD & SICD are designed to be used alongside each other:
- Sensor, processing algorithm agnostic and collection strategy
- Stored in the NITF file format with metadata in XML
- Excellent for vendor-agnostic automated data processing
Compensated Phase History Data (CPHD)
Compensated Phase History Data (CPHD) product provides a sensor-independent data structure and file format for both the storage and transmission of SAR Phase History Data (PHD). PHD signal arrays from many SAR sensors are accommodated by the data structure & supports monostatic and bistatic SAR data sets. There is compensation for the data regarding hardware timing and platform motion. The product includes metadata to describe the collection geometry and the PHD signal arrays contained in thus product. CPHD is only provided by ICEYE when requested as a custom order.
ICEYE provides CPHD that is:
- Compensated for hardware timing and platform motion
- Accommodates the Phase History Data (PHD) signal arrays from a variety of SAR sensors that sensor-independent
- Has a complete metadata set describing collection geometry and the included PHD arrays
- Stored in a binary CPHD file format that is built for thus purpose