DigitalGlobe operates a range of high spatial resolution satellite sensors. These include(d) Ikonos, QuickBird, GeoEye-1 and WorldView-1, -2 and -3. All these sensors record data in multispectral (MS) as well as panchromatic bands, apart from WorldView-1, which has only a panchromatic band. The MS channels are mostly blue, green, red and NIR, while WorldView-2 and -3 have additional bands in the red-edge and shortwave infrared part of the EM spectrum (Figure 3.1).
The spatial resolution of these images ranges from 0.31 m (in WorldView-3) to 0.82 m (in IKONOS) (i.e., for the panchromatic band). The high spatial resolution is partly due to the low altitudes at which the satellites operate (400–800 km). But it is obtained at the expense of (1) the spatial coverage of the images and temporal resolution (revisit time). In other words, compared to moderate/low spatial resolution sensors like Landsat and MODIS, image scenes obtained by DG sensors cover a smaller portion of the earth’s surface (ca. 11–18 km swath width). This means that one needs to acquire many scenes to cover a large area (e.g., the area covered by one Landsat scene).
This notwithstanding, images from DG satellites are used for a wide range of applications including agricultural management (Ozdarici-Ok et al., 2015), land (cadaster) management, natural disaster management, mining, engineering and construction due to their superior spatial resolution. DG images have also been found useful in coastal monitoring, generation of 3D digital terrain and surface models.
For agricultural applications, especially in smallholder systems, the high spatial resolution of DG satellite images enables the detection of the typical small field sizes and achieves a better representation of the heterogeneous landscape in such systems. Additionally, the inclusion of spectral channels known to be important for agricultural applications (e.g., the red-edge part of the spectrum) have increased their suitability for agricultural applications (Upadhyay et al., 2012).
DG images can be purchased either from an archive (i.e., historical) or through a tasking order. The latter case is often more expensive as it requires the sensor to be pointed specifically to your area of interest. Within the STARS project, images were acquired through both approaches for all test sites, but mostly through tasking.
The essential characteristics of DG satellites are presented in Table 3.1, while links to further details (e.g., names of spectral channels, swath width) are provided.
Table 3.1: Specifications of very high spatial resolution satellite imagery used in the context of STARS. Find here further details on IKONOS, Quickbird, GeoEye 1, WorldView-1, WorldView-2, WorldView-3