Raster Alignment (Coregistration)
Align a source GeoTIFF (orthophoto or DEM) to a reference GeoTIFF, correcting georeferencing offsets caused by GPS drift, lens distortion, or processing artifacts.
How it works
DroneDB uses two alignment modes, both based on template matching between the source and reference raster:
| Mode | Degrees of Freedom | Algorithm | Best for |
|---|---|---|---|
| Similarity (default) | 4 (translation X/Y, rotation, uniform scale) | NCC template matching + RANSAC | General misalignment, rotation, scale drift |
| Translation | 2 (translation X/Y only) | Phase correlation | Small GPS offsets, faster execution |
The aligned output is written as a Cloud-Optimized GeoTIFF (COG) reprojected to EPSG:3857 (Web Mercator).
CLI
ddb align -i source.tif -r reference.tif -o aligned.tif
Options
| Option | Description |
|---|---|
-i, --input | Source GeoTIFF to align (required) |
-r, --reference | Reference GeoTIFF (required) |
-o, --output | Output path for aligned COG (required) |
-m, --mode | Alignment mode: similarity (default) or translation |
--validate | Validate alignment parameters without writing output |
--no-seed | Disable phase-correlation seed (use only NCC template matching) |
Validate without applying
Check if alignment is feasible and preview the estimated transform:
ddb align -i source.tif -r reference.tif --validate
The command outputs a JSON report with CRS compatibility, overlap percentage, GSD comparison, and estimated shift values.
Examples
# Align orthophoto to a high-accuracy reference (default similarity mode)
ddb align -i orthophoto.tif -r reference.tif -o aligned.tif
# Translation-only alignment (faster, for small GPS offsets)
ddb align -i orthophoto.tif -r reference.tif -o aligned.tif -m translation
# Validate without applying
ddb align -i orthophoto.tif -r reference.tif --validate
In Hub
Open a dataset containing at least two GeoRaster entries. Select one as the source and another as the reference, then use the Align Raster toolbar button or processing task. The aligned result is added to the dataset as a new COG entry.
Pre-flight checks
Before alignment, DroneDB validates:
- CRS compatibility: Source and reference must share the same or compatible coordinate reference systems
- Overlap: Rasters must have sufficient spatial overlap (minimum 20% by default)
- GSD comparison: Ground sample distance should be within a reasonable ratio
- Raster type: Both inputs must be single-band or multi-band rasters of the same type
Use cases
- Correct GPS drift: Align an orthophoto generated from drone imagery to a survey-grade reference
- Match multiple surveys: Coregister orthophotos from different flights to the same coordinate frame
- DEM alignment: Align a processed DEM to a reference elevation model for accurate volume calculations