Spatial Resolution Assessment of Images from BlackSky, SuperDove and WorldView-2/-3

Options are more numerous now than ever for scientists interested in satellite-based earth observations. With the quick rise of commercial private-sector satellite sensors, independent evaluations of their quality are needed. Unlike government sensors, commercial sensors often come with proprietary information, as is the nature of the private sector. However, users of this data need to know the true quality, so they can choose the appropriate sensor data to meet their research and application goals. Most of these projects include situations that are large-scale and time-sensitive such as agricultural activities or flooding events. If the chosen sensor turns out to be inadequate for the task, it is too late to turn to observations with another sensor.

Here, we provide updates to our ongoing evaluation of sensor spatial resolution and band-to-band registration of 3 companies’ sensors: BlackSky’s Globals, Planet’s SuperDoves, and Maxar’s WordView-2 and Worldview-3. We are working on Planet’s Dove-R series as well. Sensor spatial resolution is assessed with the commonly used knife-edge method at globally distributed large black and white checkerboards at well-recognized Cal/Val sites. Taking advantage of the crosshair in the checkerboards, we develop a new, precise, method to assess band-to-band registration (BBR) by calculating any jitter of the crosshair across bands as band misalignment.

We find that images from BlackSky’s Globals sensors are oversampled by about 2 pixels (~2m sensor resolution over a 1 m grid size), but they improve with sensor generation. Images from Planet’s SuperDoves are oversampled by over 3 pixels (~9m sensor resolution over a 3 m grid size) with a slight improvement in both time in orbit and sensor generation. WorldView-2 & 3 sensors both have a different pixel gris sice for their panchromatic and multispectral bands, and both perform close to advertised. Sensor spatial resolution from WorldView-2 & -3 panchromatic resolution is ~0.6 m on a 0.41m grid, and ~0.4 m over a .31 m grid size respectively. WorldView-2 & -3 multispectral resolution is ~2.5 m over a 1.64 m grid size and 1.7 m over a 1.24 m grid size, respectively. All band-to-band registration examined is excellent.