I have generated DEMs (bare earth) from Lidar data. For computational reasons, I have processed via ArcGis the lidar files in chunks, so I came up with different single DEMs.
After, I used "Mosaic to New Raster" tool, and created a single DEM raster.
I noticed that there are some gaps (lines) along the junctions between the original single DEM rasters (from which I got the single huge raster).
I tried this function in the raster calculator:
Con(IsNull("raster"), FocalStatistics("raster", NbrRectangle(5,5, "CELL"), "MEAN"), "raster")
where "raster" is the name of the single huge DEM.
The problem is that the gaps are still there. Any suggestion?
Best Answer
I support the answer by radouxju, but would like to add:
As you have chosen to do this in chunks (good idea! you can process multiple chunks simultaneously) I recommend using an overlap of ~1k with your tiles.
You have not elaborated on how you create the DEM from LiDAR data but lets assume that you are using LiDAR->MultiPoint->Terrain->Raster DEM workflow or the new LAS Dataset to Raster tool. Both of these methods employ triangulation to fill in the blanks where there are no returns like water areas and points that don't match ground class (2 and 8). At the ephemera the triangulation becomes more erratic and will lead to mismatches over void areas.
With a ~1k overlap the triangulation is pinned down by the other side of the void, then trim the tiles back to 1/2 the overlap to get rid of the dodgy data. Guaranteed no gaps!
I would (and do) start with a grid/AOI and subdivide it to make the areas of processing to ensure that everything is covered and nothing is missed. Before exporting the raster look at the snap raster environment setting - this will ensure that the tiles' cell edges line up and resampling is not performed during the mosaic - which would slow it down and hurt your accuracy.