Circa 2000 Landsat ETM+ mosaic of northern Canada

A mosaic of northern Canada above the tree line was produced from public domain 
Landsat ETM+ level L1G bands 3, 4 and 5 ortho-imagery available through the 
Centre for Topographic Information of Natural Resources Canada. Radiometric 
normalization was necessary due to different acquisition times among the 446 
individual scenes in this mosaic. A highly automated radiometric normalization 
technique was performed to match scenes to a common radiometric reference 
consisting of a coarse (1km) apparent reflectance 2000 growing season composite 
image generated at CCRS from VGT-S01 data from SPOT’s VEGETATION sensor. 
Normalization involved resampling individual Landsat scenes to 1 km resolution 
using the VGT point spread function and generating band-specific normalization 
coefficients between Landsat and VGT using a robust regression technique called 
Thiel-Sen. This technique has been shown to produce optimal consistency among 
Landsat scenes in Olthof et al., 2005, and is highly automated allowing 
production of a mosaic of this size. 

These data are available in geo-tiff format with 57173 columns and 32914 rows at 
90 m resolution obtained by resampling 30 m Landsat data. More information on 
the processing chain used to generate these data are available in Olthof, Butson, 
Fernandes, Fraser, Latifovic and Orazietti (2005). Landsat ETM+ mosaic of 
northern Canada. Canadian Journal of Remote Sensing (accepted).