FGB Converter

What are FGB files?

FGB (FlatGeobuf) is a binary encoding of geographic vector data built on FlatBuffers, a serialization technique that allows data to be read directly from memory without parsing. A file begins with magic bytes, whose fourth byte gives the major version of the specification and whose last byte gives the patch level, followed by a header with the name, the envelope, the geometry type, the presence of Z, M, and time coordinates, the number of features, the coordinate reference system, the title, the description, and the schema of the attribute columns. After the header may come an optional packed Hilbert R-tree, which orders the features along a space-filling curve and lets a reader find all features inside a bounding box very quickly. The data section holds the features one after another, each with its geometry and a compact block of properties. The format deliberately does not support random writes, so that data can be clustered for fast spatial filtering and written as a stream, and the index can be left out when it is not needed. Compression is not part of the format, so random access is preserved, and a file on a web server can be read partially through HTTP range requests. Because FlatGeobuf is vector data, converting it to graphics means rendering the features on a canvas in the coordinate system of the data, colored by an attribute if wanted, and saving the picture as PNG, JPEG, TIFF, or GeoTIFF with a chosen resolution. Supported by GeoServer.