GDAL Nodata and Drone Processing Pipeline

Due to a nodata tag issue within the GeoTiff standard, Pix4D doesn’t generate the nodata value in a GDAL compliant manner. As such, when importing GeoTiffs into software using GDAL (like QGIS or Mapbox) the nodata value is black, meaning overlapping layer issues. Additionally, for an unknown reason, Mapbox does not deal with multiple GeoTiffs in the same manner as it displays .mbtiles, pixellating uploaded GeoTiffs. This short blog presents a processing pipeline to deal with both of these issues.

The solution for translating the nodata values has been documented here: https://geozoneblog.wordpress.com/2013/02/26/troubles-tiff-no-data-values-floating-point. I’ve written a simple bash script to convert this in a UNIX environment is here: https://github.com/WorldBank-Transport/TanzaniaDrones/blob/master/transparency_batch.sh. Basically, run the script in the folder where files are found and it will iterate through each file, translating the nodata tag value to be GDAL compliant.

Once you’ve got the nodata/transparency values resolved, it’s quite easy to add your Geotiffs to Mapbox’s Tilemill. Export your resulting map as .mbtiles and upload this to Mapbox as a tiles. In the Mapbox Studio Classic interface, add this to a map and voilà, a drone imagery online.

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