The GeoTiff File Format

with

GeoTrellis and Scala

Johan Stenberg / @johanstenbergg

How do you read GeoTiffs on the JVM?

• GDAL, Geospatial C lib, fast!

• GeoTools, Geospatial Java lib, speed?

Why yet another GeoTiff Reader?

• GeoTools large dependency
• GDAL Java bindings hard to install
• Go-To raster file format at GeoTrellis
• GeoTrellis is all about speed, everything optimized and benchmarked

What is the GeoTiff file format?

• Extension to the Tiff File Format
• Used for images with Geospatial Metadata
• Adds a bounding box and the CRS through tags

Geodata?

• Bounding Box easy to read
• Coordinate Reference System horrible to read
• Turn it into a proj4 string and use the proj4j lib to read

Compressions

• Huffman, CCITT3, CCITT4, Packbits
• LZW
• Zip

Benchmark Time!

Benchmark Disclaimer

• Ran on my development computer
• Conducted with Caliper
• Microbenchmarks, look at relative speed, not speed
• GDAL is read through the Java bindings, into GeoTrellis rasters
• GeoTools is also turned into GeoTrellis rasters

~same for CCITT3 and CCITT4

~same for CCITT3 and CCITT4

Sidenote about Speed

• Scala slow when using functional mappings
• Arrays, while loops and bit operations
• Skip Big-O time complexity analyzation (O(n) - duh), use microbenchmarks

Future?

• Tons of compressions, JPEG hard but needed
• Keep up to date with custom tags
• Add a shape file reader (GeoTools is fast!)

Thanks!

Benchmarks found at https://github.com/geotrellis/benchmark