What does satellite image resolution like 50 cm, 1 m, or 5 m mean?
Asked 9/26/2017
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I’m looking at sample satellite images with large pixel dimensions, such as 11,000 × 9,000 pixels, and they list resolutions like 50 cm, 65 cm, 1 m, 1.5 m, and 5 m. What do these resolution numbers mean in practice for a satellite image?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
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Spatial resolution in Remote Sensing is normally expressed in distance per sample rather than samples per unit distance. The same information is there, it's just expressed as the reciprocal of what is usual in normal graphics fields. The "per sample/pixel/whatever" is normally dropped as well and as it is considered implicit.
So a resolution of 0.5 m is really 0.5 m/px, which is 2 px/m or 0.0508 DPI.
This means that the pixels on the ground are squares that size (at least on average, under ideal conditions) A 0.5 m resolution raster data set has pixels that are 0.5 m squares of the Earth's surface. This gets more complicated once you start considering projection of the curved surface of the earth into a flat raster grid.
Originally by user68716. Source · Licensed CC BY-SA 4.0
user68716
8y ago
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Generated from our catalog & community — verify before relying on it.
In satellite imagery, those numbers usually mean spatial resolution: the ground area represented by each pixel, or roughly the smallest detail you can distinguish.
So:
- 50 cm resolution ≈ 0.5 m per pixel
- 1 m resolution ≈ 1 m per pixel
- 5 m resolution ≈ 5 m per pixel
A 0.5 m image means each pixel covers about a 0.5 m × 0.5 m square on the ground. Higher spatial resolution means smaller ground areas per pixel and therefore finer visible detail.
Another way to say it: a 1 m image can generally separate objects about 1 m apart, but not details much smaller than that.
This is different from image pixel dimensions like 11,000 × 9,000, which only tell you how many pixels are in the file. To know how much ground the image covers, you combine both numbers. For example, at 0.5 m/pixel, an 11,000-pixel width would cover about 5,500 m on the ground.
In remote sensing, resolution is commonly expressed as distance per pixel rather than pixels per inch or DPI.
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