determineProjection(sources) {
    const firstSource = sources[0];
    for (let i = firstSource.length - 1; i >= 0; --i) {
      const image = firstSource[i];
      const projection = getProjection(image);
      if (projection) {
        this.projection = projection;
        break;
      }
    }
  }
Determine the projection of the images in this GeoTIFF.
The default implementation looks at the ProjectedCSTypeGeoKey and the GeographicTypeGeoKey
of each image in turn.
You can override this method in a subclass to support more projections.

@param {Array<Array<GeoTIFFImage>>} sources Each source is a list of images
from a single GeoTIFF.