In my previous post, I explained how to pan-sharpen individual .tifs of high-resolution Worldview-3 satellite imagery. Worldview-3 satellite imagery is provided as a series of .tif tiles covering the area purchased, but because each .tif tile has a slightly different histogram (the frequency of each colour within the image varies from .tif to .tif) the imagery exhibits abrupt discontinuities at the edges of the .tifs.

Mosaicking

These .tifs now need mosaicking into a single raster image, providing a consistent colour map, and permitting further research into the entire dataset. There are various mosaicking tools available in ArcGIS. Which you choose depends on what you intend to do with the data, but I am going to use the Mosaic to New Raster tool of the Data Management>Raster>Raster Processing toolset of ArcTools.

The tool asks for the rasters to mosaic, the output folder, the output filename, the coordinate reference system, pixel type, number of bands, and the mosaic and colourmap operators. Most of these are fairly straightforward, but it’s worth noting that the filename needs to include the (e.g. .tif) extension, and the number of bands needs to match the number in the original rasters. The final part of the Mosaic to New Raster tool asks for the ‘mosaic Operator’ and the ‘Mosaic Colour Map Mode’. The ‘Mosaic Operator’ refers to the method of mosaicking overlapping areas. The Worldview-3 tiles shouldn’t have a significant overlap, but I prefer to use the ‘Blend’ operator, which blends the data in the overlapping area. Similarly, the Mosaic Colour Map Mode’ determines which of the tiles should provide the colour map for the new mosaicked raster. Again I prefer ‘Match’, which considers all the colourmaps. You can watch a video of me mosaicking the pan-sharpened .tifs on my Youtube Channel or in the embedded link above.

The resulting pan-sharpened, mosaicked imagery provides a much better base map of the Asyut area:

Acknowledgements

All the images in this blog post were created using ArcGIS® software by Esri. ArcGIS® and ArcMap™ are the intellectual property of Esri and are used herein under license. Copyright © Esri. All rights reserved. For more information about Esri® software, please visit http://www.esri.com.

Worldview-3 imagery © 2018 DigitalGlobe Inc. supplied by European Space Imaging.