Gridding entire shape area based on shape elevation

JustinK

Hello,

I am attempting to grid square elevation data in shapefile format. It seems as GM grids the data based on square area elevation using the bottom left corner point of the square, not the entire square shape. I am trying to create pixelated square grid, where the entire square is one shade of color, based on the grids elevation variable (no blending in the square).  The attached image shows the elevation grid. Currently, the squares are gridded using the bottom left corner and the grid elevation. I would like each square as one solid color. 

Thanks for the Help.
Justin