Tiled Vegetation Indices

Ruby on Rails web-application that leverages libvips image processing library and Leaflet interactive maps library to apply Vegetation Indices (VIs) on map tiles.

The approach was taken after analyzing how DroneDeploy works with VIs.

It is being published as open source to demonstrate how WebODM contributors can apply VIs on-the-fly on map tiles. This approach avoids the need to store different tiles for each VI.

Approach

It is generated a thumbnail of the full orthophoto. Then it is applied each one of the implemented indices on the thumbnail and is saved a histogram of each index result.

The histogram is then used to calculate a min and max used to "clip" results bellow/above min/max on individual tiles.

Implemented Indices

RGB based:

• VARI
• GLI
• IOR
• NGRI

NIR based:

• NDVI
• BAI
• SAVI
• MNLI
• MSR
• RDVI
• TDVI
• OSAVI
• LAI

Screen Capture

RGB based VARI

NIR based NDVI

Where to look

/app/lib/vegetation_index.rb

/app/controllers/vegetation_index_controller.rb

/app/assets/javascripts/map.js

JavaScript Libraries Used

Leaflet

Leaflet.AutoLayers

Chartist

jQuery 3.4.0

Multirange

d3-color

d3-interpolate

d3-scale-chromatic

Requeriments

libvips

Ruby

Ruby on Rails