GeoEye and the Humanitarian OpenStreetMap Team (HOT) are collaborating to trace new satellite imagery of Salajar Island, Indonesia, an under-mapped area in OpenStreetMap. This is part of HOT’s larger work in Indonesia organizing workshops, competitions, and mapping events to provide detailed OpenStreetMap maps for use by disaster first-responders and policymakers to aid in the country’s emergency preparedness efforts. To help HOT’s tracing efforts we processed imagery for Salajar Island from the GeoEye-1 satellite, which captures panchromatic (black and white) images at a resolution of 0.5 meters per pixel, and multispectral imagery (red, green, blue and near infrared) at a spatial resolution of 1.65 meters. A key step in our data processing was pansharpening, which merges the lower-resolution color image with the higher-resolution panchromatic one.
Here is a walk through of how we used open source geospatial libraries to turn GeoEye’s raw source imagery into a webmap rendered in TileMill and available through MapBox, which HOT’s team will use in its tracing efforts. Check out our final map of Salajar Island, and stay tuned for more information on a micro-site from GeoEye to facilitate the process and tracing results from HOT.
Pansharpening satellite images for better clarity
One way to take advantage of the higher resolution panchromatic image is to use it to pansharpen the lower resolution multispectral images, which generates a natural color RGB image with the spatial resolution of the panchromatic image.