I am working with AWD3D-30m DEM which has many gaps (missing values). Can I utilize an older ASTER or SRTM DEM to predict that? Please answer in detail on what techniques to adopt.
If you are unaware of the differences in techniques, here is a quick introduction to the different methods that one can use while kriging a raster surface to fix NA values.
Firstly, one could use the Spatial Analyst extension in ArcMap to use the Kriging tool(Alternately, you could use the 3D Analyst extension). Below is a snapshot.
Above, one can choose the appropriate method, along with selecting the radius of cells you would like to use to interpolate values from.
Secondly, and I prefer this method, See - fill the gaps using nearest neighbors. This question has been answered in detail using an example code written in R.