I have metadata in my .dat file that tells me that my cell size is 0.200 degrees longitude. I want to import this file into GIS and convert my points to raster.
My file is very simple: it has x, y coordinates and the environmental variable. Its coordinate system is in NAD83.
I am wondering what value I have to input for the cell size when I am using the point to raster toolset in ArcMap. I have two different files with two different resolutions (one is the 0.200 degrees longitude and the other is 3km2) and no other raster file to compare it to; and so for cell size do I input 0.2 and 3 respectively.
NAD83 is a geographic coordinate system based on ellipsoid. The measure unit of longitude and latitude (indirectly length) on ellipsoid is DMS (degrees, minutes and seconds).
Conversion between angular and linear units is not so simple, because it depends on geographic latitude. As we move away from the equator, parallels become smaller, so one degree becomes shorter in linear units (e.g. meters).
We could use the length of meridian for rough conversion in meters because all meridians have the same length.
One angular second is approximately 30,7 meters long. 0,2 degrees is 720 seconds, so the cell size (length) is about 22,1 km. Second raster probably hasn't cell area 3 km2 because resolution is defined by lenght. That means it has lenght between points 3 km. If cell area is 3 km2, then length is 1,73 km.
Obviously, you have a problem with defining the measure units. Maybe you could transform data in some projection (which uses rectangular coordinates xy and meters as measure units), so it would be easier and more intuitive to define resolution in meters.
BTW, which software do you use?
Since your data have x,y coordinates at each point, I suggest you check some adjacent points to determine the distance between them. Then you can decide what the resolution is. Or, as Tomislav said, transform the point layer to a projected coordinate system, then check some adjacent points to find the resolution in meters.
I think you should go by the simple suggestion of projecting from geographic to rectangular using the rectangular coordinate system of your working area. Every country or location has a specified coordinate system. After projecting to rectangular, you specify the cell size equivalent to the square toot of 3km2 so that you can have the same resolution for both rasters to enable you compare. If the cell sizes are different, you cant compare them in ArcGIS for instance. I don't know of other softwares. Best wishes
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