SlantView's soil and shadow filters can be used to isolate vegetation content across a wide variety of crops and field conditions.
Introduction to Filtering
The following animations show SlantView's filtering tools simultaneously highlighting and removing non-crop content—including shadows between rows and areas of bare soil.
To make precise adjustments to soil and shadow thresholds with visual feedback:
- Press the F7 key when the Image Window is active. The Shadow and Soil Filter settings will be displayed at the top of the Image Window, shown boxed in red in Figure 6.
- (Optional) Bring both filters down to zero to see the exact content each filter identifies as the strength is increased.
- Increase the Shadow Filter until all shadows have been greyed out, by holding down the Ctrl key while scrolling the mouse wheel, or use the on-screen slider bar.
- Increase the Soil Filter until all non-crop content has been greyed out, by holding down the Ctrl + Shift keys while scrolling the mouse wheel, or use the on-screen slider bar.
- Move back to the Map Window by double-clicking or pressing the Tab key, and check a few images across the map with the new filter thresholds before recalculating the maps.
- Recalculate the map by clicking the recalculate maps icon on the lower right side of the settings window or the far right button on the toolbar.
The Shadow and Soil Filters in the Image Window in Figure 6 (right side), have been zeroed out.
Figure 7: Left: Shadow Filtering only, Right: combination Shadow and Soil Filtering
If non-plant material accounts for most of the red areas of your Stress Map, manually adjusted filters may be more effective at highlighting potential problem areas within a field. After visually adjusting Soiland Shadow Filters to separate plant material from soil, roadways, equipment, and other non-plant material, recalculate maps based on your new thresholds.
Filtered vs Unfiltered NDVI
When active in the Image Window, press the number keys 1, 2, and 3 to show the Green, Red, and Red Edge NDVI high resolution views. In the Settings—Processing menu, checking the Filtered box next to the NDVI map product option will remove non-crop content and display NDVI maps similar to those in Figure 1. Leaving the Filtered box unchecked will display NDVI views as in Figure 2, where non-crop content is not blacked out.
Figure 1: green (left), red (center), and red edge (right) filtered NDVI views
Figure 2: green (left), red (center), and red edge (right) unfiltered NDVI views