Mosaics for avoiding edge effects

Introduction

When analysing raster data for conditions that relate to a neighbourhood, edge effects are inevitable. To avoid that, Karttur’s GeoImagine Framework can generated virtual mosaics that enlarge every tile by using all 8 neighbours. Any neighbourhood analysis can then be done using the enlarged, virtual mosaic, while limiting the output to the core tile region. The result will be a set of seamless tiles without any edge effects.

MosaicAdjacentTiles

The process for generating enlarged virtual tiles is MosaicAdjacentTiles. The process operates on regions defined for any projection system (e.g. MODIS SIN or EASE-grids).

json

All required parameters have default values. The virtual tile will always be saved as a virtual GDAL dataset, with the extension replaced to .vrt. The default expansion is 101 cells in all directions.

Hide/Show MosaicAdjacentTiles.json

  
{
  "userproject": {
    "userid": "karttur",
    "projectid": "karttur-arcticdemext",
    "tractid": "karttur-arcticdemext",
    "siteid": "*",
    "plotid": "*",
    "system": "modis"
  },
  "period": {
    "timestep": "static"
  },
  "process": [
    {
      "processid": "MosaicAdjacentTiles",
      "version": "1.3",
      "overwrite": false,
      "parameters": {
        "asscript": true,
      },
      "srcpath": {
        "volume": "Ancillary",
        "hdr": "tif"
      },
      "dstpath": {
        "volume": "Ancillary",
        "hdr": "vrt"
      },
      "srccomp": [
        {
        	"dem500": {
        		"source": "NGA-NSF",
        		"product": "arcticdem",
        		"content": "dem",
        		"layerid": "dem500",
        		"prefix": "dem500",
        		"suffix": "v30"
          }
        }
      ],
      "dstcopy": [
        {
          "dem500": {
            "srccomp": "dem_arcticdem"
          }
        }
      ]
    }
  ]
}

Applying the enlarged virtual mosaics

When running processes that rely on neighborhood analysis you apply the enlarged tiles by setting the parameter mosaic to true.