Cloud Optimized GeoTiffs

While Felt can read many raster formats, storing your data as a Cloud Optimized Geotiff (COGs) allows efficient access of subsets of data for fast viewing.

Configuration

Required?
Configuration option
Recommended values

Mandatory

Overview resampling

  • bilinear for floating point data

  • nearest for integer or categorical data

Mandatory

Block size

256x256 or 512x512

Recommended

Compression scheme

  • YCbCr with JPG compression for 8-bit RGB data

  • DEFLATE, LZW, or ZSTD for floating point data

Recommended

Transparency

Set an explicit Nodata mask band

Recommended*

Summary statistics

Min, max, mean and standard deviation. Stored in the header, per the GeoTIFF specification

Converting raster files to Cloud Optimized GeoTIFFs

  1. Install the GDAL command line tools. If you’re using homebrew on MacOS, you can do this with brew install gdal

  2. Use the gdal_translate command with the COG output format and the -stats flag. This will create a COG with summary stats and overviews that will be most efficiently streamed into Felt.

Example for floating-point data
$ gdal_translate -stats -of COG -resampling bilinear -co COMPRESS=LWZ {input}.tif {output}.tif
Example for integer data
$ gdal_translate -stats -of COG -resampling nearest -co COMPRESS=JPEG {input}.tif {output}.tif

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