Spectral indices
Spectral indices are mathematical formulas that highlight specific features in multispectral imagery. TerraQuery automatically detects which indices are available based on the bands in your TIFF.
RGB indices (all cameras)
Available for any RGB orthomosaic:
| Index | Full name | What it shows |
|---|---|---|
| VARI | Visible Atmospherically Resistant Index | Vegetation health. (G−R)/(G+R−B) |
| ExG | Excess Green Index | Green vegetation vs bare soil. 2G−R−B |
| GLI | Green Leaf Index | Living green vegetation. (2G−R−B)/(2G+R+B) |
| NGRDI | Normalized Green-Red Difference Index | Crop health. (G−R)/(G+R) |
Multispectral indices (NIR required)
Available when the TIFF has a Near-Infrared band:
| Index | Full name | What it shows |
|---|---|---|
| NDVI | Normalized Difference Vegetation Index | Vegetation density & health. (NIR−R)/(NIR+R) |
| SAVI | Soil-Adjusted Vegetation Index | Vegetation with exposed soil. (NIR−R)/(NIR+R+0.5)×1.5 |
| EVI | Enhanced Vegetation Index | High-biomass areas. 2.5×(NIR−R)/(NIR+6R−7.5B+1) |
Red Edge indices (RedEdge band required)
Available for cameras with a dedicated RedEdge band (e.g. MicaSense):
| Index | Full name | What it shows |
|---|---|---|
| NDRE | Normalized Difference Red Edge | Crop nitrogen stress, canopy density. (NIR−RE)/(NIR+RE) |
How band detection works
TerraQuery automatically identifies which band in your TIFF corresponds to which spectral role:
- NIR — the band with the highest mean reflectance
- Blue — the band with the lowest mean reflectance
- Red — the band with the second-lowest mean reflectance
- Green — the band with the third-lowest mean reflectance
- RedEdge — the band at the reflectance midpoint between Red and NIR
Bands where mean reflectance is below 20 (water absorption bands) are excluded from role assignment.
Color scale (dynamic stretch)
The colormap for each index is dynamically stretched to the p2–p98 percentile range of the actual pixel values in your image. The full color range is always used regardless of absolute values — low-contrast images still show meaningful variation.
On the standard red-to-green scale:
- Dark red / red — low or negative values (stressed vegetation, bare soil)
- Yellow — mid-range values
- Green / bright green — high positive values (healthy dense vegetation)