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I have a raster data with spatial reference GCS-WGS-1984 (datum D-WGS-1984). Its cell size is mentioned as (0.00045, 0.00045) in degrees.

How can I convert this resolution in meters (i.e. linear unit)?

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Easiest way is to convert the raster to a projected system, and get the cell size directly in meters.

That not being possible, or desirable, you can still convert lat/lon values to metric values, but you'll run into an accuracy problem. This is because, 1º of distance represents different values in metric units depending on your location and bearing (0.00045º is about 50m around the Equator, but about 30m around London). There are ways to calculate it, but you'll be generalizing somewhat your results.

If accuracy is not very important and you only want an overall idea of the cell size, you can either do it with the Haversine formula (easier but less precise) or Vincenty's inverse formula (more precise, but way more complicated).

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    Notice also that cell size in meters is different in East-West and South-North directions. Just to clarify if meaning of "bearing" is not familiar. – user30184 Feb 8 '18 at 20:06
  • How can one convert a single 'resolution in degrees' value to a single 'resolution in meters' value with the Haversine formula? The formula itself determines distance, which means at least two pairs of coordinates are required. – Nikos Alexandris Dec 28 '20 at 22:22
  • @Nikos The resolution mentioned by OP is a measure of distance. Specifically, a square of 0.00045 x 0.00045 degrees, these degrees being the distance between two adjacent vertices of the cell. To calculate this distance the vertex coordinates themselves are not needed, just two orthogonal sides (0.00045 for each), and the angle between them (which will be 45° here since the sides are equal-length). – Roberto Ribeiro Dec 30 '20 at 0:50
  • @RobertoRibeiro Indeed! Thank you. – Nikos Alexandris Dec 30 '20 at 11:12
  • @RobertoRibeiro Indeed! Thank you. – Nikos Alexandris Dec 30 '20 at 11:12

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