# "10 m resolution" - Expressed as screen resolution (or other way photography noob can understand)?

The X-Sat satellite captures images of Earth "with a 10 m resolution multispectral (three spectral bands in the visible and near infrared spectrum) instrument". What does this mean? Particularly, how would "10 m resolution" be expressed if it was to describe a screen resolution? Other ways of describing this resolution is also welcome.

The web page you linked uses term Spatial resolution. It is to describe the resolving power of the imaging device they have up there, i.e. the ability to separate points of an object which in this case is the surface of the Earth.

Ten meters resolution tells us that the camera located 685 kilometers above sea-level is able to tell apart objects that are 10 meters from each others. On a dark surface of a parking lot two lightcolored cars will appear as single pixel if they are closer than 10 meters to each others. More than 10 meters apart the cars will produce two pixels on the image.

What the 10 meter resolution means on your computer screen? I presume you have a wide screen display of 1920 pixels horizontal. The 10 meter resolution means that if you go "pixel peeping" the image, you will see 10 meters of Earth surface per each pixel on your display, resulting in 19,2 kilometers wide patch of ground if you view it on full screen. However they say on that wikipedia page that the imaging device is able to capture a 50 kilometer wide patch of land as the satellite moves across the sky. This you divide with 10 meters to get the horizontal resolution of the imaging sensor they have.

50 km is 50.000 meters divided by 10 meters equals 5000 pixels wide sensor. Now, that is a number we can understand easily. In real life it might not be as simple as that, but I believe this already answers your question.

A sample of 10 meter resolution imagery: Central Kalimantan maximum resolution

In the rightmost picture you can easily see a wide river and a narrower river come together, and supposedly farmlands divided into rectangles by a crisscross of ditches, and some white blobs that are clouds. The methods and objectives are explained at http://www.eorc.jaxa.jp/ALOS/en/guide/forestmap_oct2010.htm

In its original form — and the sense used here — resolution means "the level of detail which can be resolved". That is, from its orbit, this camera can resolve individual objection the ground that are approximately 10 meters in size. This may correspond to the number and size of pixels on the sensor, but there also might be other limiting factors (such as the quality of the optics).

But the word "resolution", somewhat unfortunately, has another meaning in computer graphics. We call a screen with a lot of pixels "high resolution". That's because if the screen is the same size (and they mostly were, in the early days of computers) more more pixels lets you show more detail, and in effect more resolution in the original sense. This is the term you are familiar with, and it is basically unrelated.

We sometimes refer to the number of pixels (usually in terms of megapixels) on camera's sensor as "resolution". Another way to think of this is that each element of the complete system has its own resolution, and that each part is its own limiting factor. The lens, the sensor, the post-processing — the level of detail each can resolve puts a cap on the overall resolution. And it can go further back: stability of the platform can be a limit, whether it be a satellite spinning in orbit or a flimsy tripod. Or on the other side, once the image is captured, the display screen or printer you use is another potential bottleneck. (But in this case, I think they are just talking about the captured image regardless of display.)

In this context "10 m resolution" probably means each pixel in the satelite image ideally maps to a 10x10 meter rectangle on the ground.

This has absolutely nothing to do with "screen size", whatever that is supposed to mean, so the rest of your question can't be answered.

I work in remote sensing sciences. A good summary of the spatial resolution concept for satellite images has been done by Duveiller (2010) and completes some of the other answers:

Spatial resolution is a complex concept for which there is no single definition (Townshend, 1980). A strong simplification is often made in which spatial resolution is considered to be equivalent to the ground projection of the pixel.However, the pixel itself is not a true geographical object (Fisher, 1997) and it is often larger than what people would like it to be (Cracknell, 1998).

Earth observation by remote sensing consists in measuring a property of the planet's surface, generally the electromagnetic radiation reflected or emitted by the surface,which is characterized by a certain variability in space. The spatial heterogeneity is generally structured by various sets of objects scattered over the landscape. In remotely sensed images, these spatial structures are recognizable by the fact that their spectral properties are more homogeneous within them than between them and other scene elements (Jupp et al., 1988). The scale of spatial variation within an image relates to the size and distribution of spatial structures across the surface. Assuming some periodicity in the repetition of these structures, the surface can be described in terms of spatial frequencies. High spatial frequencies correspond to small spatial structures while small spatial frequencies characterize larger object and smoother spatial variations. The spatial resolution of an instrument relates to its ability to resolve high spatial frequencies. This capacity depends mainly on 3 characteristics of the instrument which will be described hereafter: the ground sampling distance, the modulation transfer function and the signal-to-noise ratio.