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Area weighted average for light data

Question asked by Jean.Philippe.Wan on Nov 11, 2016

Hi,

 

I am a new user of ArcGIS and GIS data.  I currently have a project where we are using light data and as a starting point we are replicating the paper by Henderson et al. In their paper, they calculate the area weighted average of light data using the AML code

 

    /* area-weighted zonal stats: total digital number*area
    ular%grd%t = zonalstats(ctryliggrid,l%grd%nm * gluareag,sum,DATA)

 

where l%grd%nm  are rasters with the light data and gluareag is an ascii file with area of grid cell in square km

 

They later divide by the country area to get the area weighted average

 

Could someone explain why l%grd%nm * gluareag creates the weighted sum at the grid level  to be used in the Zonal
Statistics?

 

Also I have a shapefile of Africa at the first administrative level, when I calculate the zonal statistics i get statistics at that level but i would also like to have it at the country level.The shapefile contains country as an attribute.

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