Generate a vegetation index

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Index generator

To generate predefined indices based on the imported images.

1. Click the Index Generator icon on the top right of the window. The INDEX GENERATOR tool opens in the left sidebar.
2. Select the Source layer first.
3. Select the vegetation index that you want to generate by checking the corresponding boxes.
4. Click GENERATE.

 
Note: Below Available indices, there is a list of the most commonly-used vegetation indices available by default in Pix4Dfields. The list of indices is different for RGB and multispectral images.

Available indices

Index Description Formula Image import type
BNDVI - Blue Normalized Difference Vegetation Index NDVI index without red channel availability, for areas sensitive to chlorophyll content. (NIR − BLUE) / (NIR + BLUE) Multispectral (excluding Sequoia)
GNDVI - Green Normalized Difference Vegetation Index NDVI index without red channel availability, for areas sensitive to chlorophyll content. (NIR − GREEN) / (NIR + GREEN) Multispectral
LCI - Leaf Chlorophyll Index

Index to assess chlorophyll content in areas of complete leaf coverage.

Value range clamp between -1 and 1.

(NIR − REDEDGE) / (NIR + RED)  Multispectral
MCARI - Modified Chlorophyll Absorption in Reflective Index Index used to measure chlorophyll concentrations including variations in the Leaf Area Index. 1.2 * (2.5 * (NIR - RED) - 1.3 * (NIR - GREEN)) / (normalized to the maximum value of RED, GREEN, and NIR bands) Multispectral
NDRE - Normalized Difference Red Edge Index sensitive to chlorophyll content in leaves against soil background effects. This index can only be formulated when the red edge band is available. (NIR − REDEDGE) / (NIR + REDEDGE) Multispectral
NDVI - Normalized Difference Vegetation Index Generic index used for leaf coverage and plant health. (NIR − RED) / (NIR + RED) Multispectral
SIPI2 - Structure Intensive Pigment Index 2

Index used in areas with high variability in canopy structure (e.g. forestry).

Value range clamp between -1 and 1.

(NIR − GREEN) / (NIR − RED) Multispectral
TGI - Triangular Greenness Index RGB index for chlorophyll sensitivity. (GREEN − (0.39 * RED) − (0.61 * BLUE)) /(normalized to the maximum value of RED, GREEN, and BLUE bands) RGB
VARI - Visible Atmospherically Resistant Index RGB index for leaf coverage. min(1; max(-1; (GREEN − RED) / (GREEN + RED − BLUE) )) RGB, MicaSense
Note 1: min(1, max(-1, ...) is clamping the values between -1 and 1.

 

Index calculator

To generate a custom index using the index calculator.

1. Open the INDEX GENERATOR by clicking the icon at the top right of the window.
2. Choose the source layer.
3. Click Create custom index below the list of available indices.
4. Name the index.
5. Enter the formula either by clicking the Operations and the Reflectance Map Bands buttons or by using your keyboard.
When a formula is valid, the PREVIEW button turns green.
6. Click the PREVIEW button to preview your index.
7. When you are satisfied with the preview, click APPLY.
8. The generated custom index appears now in the list of layers and in the map interface.

Custom indices can be created depending on the available bands from your imported images, these are listed as buttons under Reflectance Map Bands.

The Operations buttons are described below:

Operation Description
( open parenthesis
) close parenthesis
* multiplication
+ addition
- subtraction
/ division
; (semicolon) separator for functions that take more than one parameter
^ exponentiation
abs absolute value
exp exponential (e^x)
log natural logarithm
max maximum value between two arguments, the separator is ";" (semicolon)
min minimum value between two arguments, the separator is ";" (semicolon)
sqrt square root

 

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34 comments

  • Jorge Solorzano

    Hello,

    I am new to Pix4D and I am wondering if it is possible to import one RGB orthomosaic previously generated in another software such as Agisoft and calculate the TGI Index in Pix4D Mapper?

    I have several orthomosaics that have been previously generated by my colleague in metashape but I would like to calculate the TGI index in Pix4D without re-process all the datasets again since I already have the mosaics.

    I was reading the Vegetation Index Documentation and I see that the equation used for TGI is TGI = (GREEN − (0.39 * RED) − (0.61 * BLUE)) /(normalized to the maximum value of RED, GREEN, and BLUE bands). What does "Normalized to the maximum value of R,G,B bands" Mean exaclty? Do you have an example of the equation normalizing with real numbers? so I can understand better the normalization part?

    Kind Regards,

     

     

     

  • Momtanu (Pix4D)

    Jorge, You can use Pix4dFields. You can import the RGB orthomosaic and calculate indices. However, before purchasing, we will recommend to use a trail and testing. The denominator is the max value of red, green and blue bands. You are normalizing the TGI by dividing the index with the max value.

  • JACQUELIN RAMAROLAHY

    Hello,

    We have a phantom4pro to collect data.

    Which indexes are the best for showing : hydratation of cultures, rate of chorophylle, density of leafs?

    Is the camera of the p4p suitable for these outputs please.

    Best regards

  • Momtanu (Pix4D)

    Jacquelin,

    The index maps generated will only tell you which areas are stressed/unhealthy. However, you would need to scouting/ground truth validation to understand the reason for the stress. Generally, research says that plant density is directly proportional to vegetation index values from multispectral cameras. 

    Phantom 4 Pro has a RGB camera, thus you will be only able to the visual changes. Multispectral cameras have NIR/Rededge band which is beyond visual spectrum (RGB) and thus helps in the detection. You could use your phantom 4 Pro and do some tests.

    This will help: https://support.micasense.com/hc/en-us/articles/229948948-Multispectral-FAQs, https://www.mdpi.com/2072-4292/11/23/2757/pdf

     

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