What is spatial resolution?

Aggrey Muhebwa

In remote sensing, spatial resolution refers to the size of the smallest possible feature that can be displayed in a satellite image.

Imagine a satellite that is as big as a school bus trying to capture a scene size of 300m by 300m on the ground, at an altitude of about 700Km from the earth. You would need lots of cameras in order to capture all the great details. So, what space scientists and engineers do is to represent the linear dimension on the ground using a single pixel. Depending on the use of the satellite, this pixel will be encoded differently. For example, if the satellite imagery is measuring the earth’s greenness, the pixel will be a different color intensity of green.

A satellite with a resolution of 50cm per pixel takes clearer images showing finer details than a 10m per pixel resolution satellite. On the other hand, the 10m/pixel resolution satellite captures more details in a single image (larger section of land) than the former.

Consider a maize field that is 300 meters by 300 meters, and have 2 satellites, say Landsat and Sentinel 2 with resolutions of 30m and 10 meters per pixel, respectively. This means that for every 30 meters on the ground, they will be represented as a single pixel in the landsat captured imagery and every 10 meters will be represented by sentinel captured imagery. Thus, a 300m by 300m becomes a 10m by 10m image in Landsat and 30m by 30m in Sentinel 2. Sentinel 2 captures finer details, whereas Landsat captures more details.

Ultimately, as technology advances and sensors become cheaper, satellites with resolution as high as 0.31m per pixel are being launched into space. This gives hope that one day, we will be able to observe the earth from the sky in finer details.