What Is a Cloud Optimized GeoTIFF (COG)?

How Cloud Optimized GeoTIFF differs from a regular GeoTIFF, why it makes huge orthophotos open instantly in the browser, and the COG workflow in CartaX.

2026-07-17 · 2 min read

An orthophoto from a drone flight can easily be gigabytes. The classic way to share it — download, open, inspect on a powerful machine — doesn't scale. Cloud Optimized GeoTIFF (COG) solves exactly that: huge orthophotos are read from the cloud piece by piece and open instantly in the browser.

The problem: regular GeoTIFF reads poorly from the cloud

A standard GeoTIFF is a TIFF with georeferencing; its internal layout, however, was not designed for partial reads over the network. Even if you only want to look at a small area on the map, the client usually has to download most of the file.

The solution: COG's internal layout

A COG is still a 100% valid GeoTIFF — the difference is organization:

  • Tiling: the image is split into small tiles; only the tiles visible on screen are downloaded.
  • Overviews: lower-resolution copies live in the same file; zooming out reads the small copy.
  • HTTP range reads: the client requests only the byte ranges it needs.

The result: a 3 GB orthophoto appears the moment the map opens — because only a few hundred kilobytes of tiles have been fetched.

The COG workflow in CartaX

  1. Upload a raw GeoTIFF (up to 3 GB / ~1.5 gigapixels): it is converted to COG in the cloud (uses processing tokens) and served to your map as tiles.
  2. If your file is already a COG: it is auto-detected and registered token-free — usable immediately with no conversion wait. Within your storage quota you can upload much larger COGs.

Add a DSM/DTM next to your orthophoto to enable elevation readouts, profiles and volume measurement — see DSM vs DTM.

How do I produce a COG myself?

Most photogrammetry suites can export COG directly. With GDAL it is a single command:

gdal_translate input.tif output-cog.tif -of COG -co COMPRESS=DEFLATE

CartaX Studio is the desktop companion that runs this conversion on your own machine and uploads the output straight to your account.

Summary

Question Answer
Is a COG a valid GeoTIFF? Yes — every COG is a GeoTIFF; the difference is internal layout
Why is it fast? Tiling + overviews + HTTP range reads: only the visible part downloads
CartaX limits? Raw TIFF 3 GB / ~1.5 GP (with conversion); ready COGs within your storage quota
Do I need tokens? Yes for raw TIFF conversion; no for registering a ready COG