Unit of Measurement for Pixel Size in GIS
Pixel size in GIS refers to the ground area represented by a single pixel (or cell) in a raster dataset. The unit of measurement for pixel size depends on the coordinate system (spatial reference) used by the raster data:
If the raster is in a projected coordinate system (such as UTM or a national grid), the pixel size is measured in linear ground units, typically meters or feet. For example, a pixel size of 5 means each pixel covers a 5 x 5 meter area on the ground.
If the raster is in a geographic coordinate system (such as WGS84, EPSG:4326), the pixel size is measured in degrees of latitude and longitude. For example, a pixel size might be 0.0001 degrees.
"The dimensions on the ground of a single pixel in a raster, measured in map units. Pixel size is often used synonymously with cellsize.
Examples
Landsat MSS: Pixel size is 56 x 79 meters7.
Landsat TM: Pixel size is 30 x 30 meters7.
Sentinel-1 GRD: Pixel size is often 10 x 10 meters, but if the raster is stored in a geographic coordinate system, pixel size may be expressed in degrees, such as 0.0001 degrees5.
Summary Table
| Coordinate System Type | Typical Unit for Pixel Size |
|---|---|
| Projected (e.g., UTM) | Meters (m) or feet |
| Geographic (e.g., WGS84/EPSG:4326) | Degrees (°) |
Key Points
Always check the raster's coordinate system to interpret pixel size units correctly.
For most health sector microplanning applications, projected coordinate systems (meters) are preferred for easier distance and area calculations.
To convert pixel size from degrees to meters, reproject the raster to a projected coordinate system suited to your area of interest.
In summary, the unit of measurement for pixel size is determined by the raster's coordinate system: meters or feet for projected systems, and degrees for geographic systems.