1B:
This is Maxar’s most basic imagery product group. System-Ready (1B) products are radiometrically and sensor corrected. They are not geometrically corrected or mapped to a cartographic projection and ellipsoid. Image resolution varies with off-nadir angle. This product is for customers who need minimally processed imagery to control all aspects of image processing, manipulation, orthorectification and photogrammetric analysis, The imagery requires advanced remote sensing experience and image processing tools. The GSD (spatial resolution) is uniform across the entire product. The radiometric corrections applied to this product include:
– Relative radiometric response between detectors
– Non-responsive detector fill
– Conversion for absolute radiometry
3D:
Orthorectified product. Based on the process of removing image distortions introduced by the collection geometry and variable terrain and re-sampling the imagery to a specified map projection. Also referred to as ortho- correction or terrain correction.
Maxar offers a suite of orthorectified products available at different map accuracy standards.
Orthorectified Imagery products offer the highest degree of cartographic accuracy with optimized resampling, balancing, pan-sharpening and mosaicking for immediate use in GIS operations or location-based applications. When required, Maxar will acquire ground control points to achieve a user-defined product accuracy.
Map-Ready imagery products include:
– Map-Ready Orthorectified Single-Image
– Map-Ready Block-Adjusted Multi-Image
– Map-Ready Orthorectified Mosaic
4BB:
4-Band Bundle
4MS:
4-Band Multispectral
(4)PS/Pan-Sharpened:
Processed used to create a high-resolution color image by fusing Multispectral and panchromatic bands.
8BB:
8-Band Bundle
8MS:
8-Band Multispectral
ACOMP:
Atmospheric Compensation. Physically based normalization of the image values
AOI (Units):
Area of Interest. The area on the Earth that you want to view (amount identified in “SQKM”)
Bit depth:
Bit depth is the number of bits used to store information for a pixel in Maxar imagery corresponding to an unsigned integer manifested as dynamic range. Each pixel is assigned a value; the range of these values depends on your bit depth. Maxar’s satellites collect data using an 11-bit dynamic range. This allows 2,048 possible intensity values that can be assigned to a pixel.
Because computers do not read 11- or 14-bit data, Maxar takes the first 11 or 14 bits of data and stores it in a 16-bit file. Placeholders are added to account for the difference. The data still spans the 0-2,047 or 0-16,383 intensity values. 16-bit files are larger than 8-bit and require more storage space. However, 16-bit offers more information for Multispectral analysis. 8-bit data can have Dynamic Range Adjustment applied to it while 16-bit data cannot
CC:
Cubic Convolution (Resampling Kernel).
Considers the nearest 16 pixels synthesizing digital numbers using a polynomial calculation. This method produces a smoother appearance than the Nearest Neighbor method while providing slightly sharper edge detail. Not recommended for pan-sharpened products.
Date/Tasking window:
Customer-defined period of time when a collection should occur, i.e. the earliest and latest date for the tasking window is set.
DRA:
Dynamic Range Adjustment.
DRA is a customer-selected parameter for visual enhancement applied to imagery. DRA consists of two parts: Color Correction and Contrast Enhancement. It is generally intended for users who do not have the tools to custom stretch the imagery. This enhancement is strictly visual and does not affect the geographic locations of the imagery pixels. Only available for 8-bit products.
ENH:
Enhanced (Resampling Kernel).
The Enhanced Kernel uses a high pass Laplacian filter applied to the panchromatic data as a pre-processing step before pan-sharpening. The result is an image with very fine detail and excellent color balance. This option is only available for pan-sharpened products.
Footprints:
Total area covered by your image. It corresponds to the size of the captured area on the ground.
FTP:
File Transfer Protocol
GE01:
GeoEye-1 satellite
Ground Sample Distance (GSD)/Resolution:
It is defined as the Native Sensor.
Resolution and Product GSD. It is the smallest discernable feature that can be dissolved by the sensor system/The resampled image pixel size derived from GSD.
HD:
High Definition.
A proprietary technique owned by Maxar that improves the visual clarity (“acutance”) of an image.
LG01/02/03/04:
Legion (01/02/03/04)
MTF:
Modular Transfer Function (Resampling Kernel).
Uses an 8 x 8-pixel window to determine the value of the destination pixel. This is a sensor-specific kernel based on an empirical modeling of the optical and electronic properties of the sensors. This method produces the sharpest edge detail of all the methods. Not available for pan-sharpened products
NN:
Nearest Neighbour (Resampling Kernel).
Selects the radiance value from the nearest pixel in the input image and does not alter the radiance values of the original image. This method can result in a blocky or disjointed image because no averaging is performed. Not available for pan-sharpened
Off-Nadir Angle:
Off Nadir Angle (ONA) refers to the angle between the satellite’s nadir, which is directly below the satellite, and the point on the Earth’s surface which is being observed. That means that if a satellite is directly above the area of interest, the ONA will be 0°. The farther the satellite, the higher the ONA. This number influences the quality and characteristics of optical imagery collections. Geo-Eye-1, WorldView-1, WorldView-2, WorldView-3 and WorldView Legion satellites are highly agile imaging systems capable of looking at a range of off-nadir angles. Variations in off- nadir viewing angles affect revisit time, resolution and swath width. As the off-nadir view decreases, so does spatial resolution. More sampling occurs to achieve the desired Product GSD. Because the off-nadir view affects the overall collected swath width and spatial resolution, Core Imagery Products are restricted to a maximum 45° off-nadir angle. Orthorectified and High-Definition (HD) products are restricted to a maximum 30° off-nadir angle.
(OR)2A:
View-Ready Standard (formerly “(Ortho-Ready) Standard”)
View-Ready Imagery products are suitable for users requiring modest absolute accuracy and/or large area coverage. These products are radiometrically, sensor and geometrically corrected then mapped to a cartographic projection. View-Ready products provide ready-to-use imagery for value added production or analysis within customer imagery workflows and require experience with image processing tools.
The GSD (spatial resolution) is uniform across the entire product. The radiometric corrections applied to this product include:
Relative radiometric response between detectors
Non-responsive detector fill
Conversion for absolute radiometry
Map projected and workflow-ready imagery prepared for orthorectification
The sensor corrections account for internal detector geometry, optical distortion, scan distortion, any line-rate variations and registration of the Panchromatic and Multispectral bands. Geometric corrections remove spacecraft orbit position and altitude uncertainty, Earth rotation, Earth curvature and panoramic distortion. View-Ready products are rectified to a coarse Digital Elevation Model (DEM), or an average base elevation provided by the customer.
View-Ready imagery products consist of:
– View-Ready 2A: Terrain adjusted
– View-Ready OR2A (projected to an average base elevation)
– Block-Adjusted Multi-Image
PAN/Panchromatic:
A wide spectral band that is comprised of reflected light in the visible spectrum (i.e., blue, green, red and NIR). It is displayed as a black and
Resampling:
When a satellite image is acquired, the pixels do not line up with any regular grid. Resampling takes those pixels from the satellite image and aligns them to the grid. When an image is resampled, the coordinates of each pixel or the original image are transformed to their new corresponding location in the new regular coordinate system (grid). A pixel in the new grid will not generally overlay a pixel in the original grid. As a result, the intensity value, or Digital Number (DN), assigned to a cell in the output grid is determined by using the pixel values that surround its position in the original grid. This is resampling.
RGB/Natural Color:
Red, Green, Blue
Stereo:
The collection of two or more images of the same Area of Interest (AOI) from different viewing angles
Sun elevation:
The angle of the sun above the horizon
Sun Elevation Angle
Sun elevation angle is a measure of the incident angle of the sun’s rays with respect to a target. This is an indication of image lighting quality and factors into overall image quality. Higher sun elevation angles provide better lighting and higher Signal to Noise Ratio (SNR). This usually results in better overall image quality.
Variation in sun elevation angles are a function of: target location (latitude) time of year fixed sun-synchronous orbits of Geo-Eye-1, WorldView-1, WorldView-2, WorldView-3, WorldView Legion 1 and 2 satellites time of day for mid-inclination orbits of WorldView Legion 3 and 4 satellites Maxar commits to deliver imagery products with sun elevation angles greater than 15° for non-pan-sharpened products and better than 30° for pan-sharpened products. In polar and near-polar regions, sun angle compromises may be necessary, especially in autumn and winter months. In these circumstances, customers must sign a product disclaimer since imagery collected with a sun elevation angle less than the stated default values are outside Maxar’s product specification.
SWIR:
Shortwave infrared
Tiling:
Some Imagery Products cannot fit on all available media types due to their large size. Maxar offers customers the option to break up imagery into smaller pieces called tiles or a BigTIFF file format.
Tiles may be defined by pixel-based grids or by map-based coordinates.
Pixel based tiles may be defined by the following tiling schemes:
– 8k x 8k (8,192 pixels by 8,192 pixels)
– 14k x 14k (14,336 pixels by 14,336 pixels)
– 16k x 16k (16,384 by 16,384 pixels)
The BigTIFF file format is a TIFF variant to use of 64-bit offsets and supports larger file sizes.
Map-based tiles are based on map coordinates in product units (meters or feet) and are defined by tile size.
Imagery orders greater than 2 GB in file size are required to be tiled. Additionally, 4-band pan-sharpened products are recommended to be tiled at 14k x 14k or smaller due to file size.
WV01/02/03/04:
WorldView-1/-2/-3/-4 satellite