Following our successful work on map stories for Google Earth's Voyager feature, the Google Earth Outreach team asked us to help design and develop several key global layers about ocean depth, sea floor age, and sea surface temperature.
Using a range of tools, including Google Earth Engine and the venerable open source TileMill, we developed several rounds of cartographic treatments and then generated global map tiles for three layers — sea floor age, sea surface temperature, and ocean depth — along with styling and KML development for layers about volcanoes and earthquakes.
Each of the three tile layers were initially prepared as large GeoTIFFs using QGIS. In QGIS, we used global rasters and began by loading the images and symbolizing with color gradients or categories. We overlaid the data sets with a global hillshade, using composite operations to set a blending mode of "multiply" to add a shadowing detail to the sea floor age and ocean depth data sets. Once exported as GeoTIFFs, we brought each styled map image into its own TileMill project. TileMill allowed us to easily take care of two tasks. First, since we were working with marine layers, we wanted land areas to be transparent. TileMill also has composite operations, and combined with a Natural Earth Countries vector layer hosted by Mapbox on Amazon AWS, we were able to exclude the land areas from the raster images. Second, TileMill is used to export our final maps as tiles in the form of MBTiles. We then exported MBTiles to directories of tiles using the MBUtil utility. The directories of tiles were uploaded to Google Cloud Storage and linked within a KML which can be loaded into Google Earth Web.
Focus: Environment
Services: Interactive Solutions, GIS Services, Data, Cartography, Web Mapping
Project Years: 2018