There are many ways of downsampling as mentioned in Plotting image data in Julia is much slower than MATLAB - #17 by stevengj
What are best ways of downsampling for my case? See grid points of my data in scatter plot below. 
and also other photo viewed from top of sphere.
In my case i have points in 3D space having x, y and z coordinates. Each point have associated values like Density or Pressure or Velocity in x,y and z directions etc. in different arrays. If i remove a point in 3D space by downsampling then i have to downsample that point associated value in arrays having Density or Pressure or Velocity in x, y and z directions.