The following article describes how to generate vegetation indices using the default index options and how to generate a customized index using the index calculator
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Index generator
To generate predefined indices based on the imported images.
1. Click Index above the Layers Menu. The INDEX GENERATOR tool opens.
2. Select the Source layer.
3. Select the vegetation index that you want to generate by checking the corresponding boxes.
4. Click Generate.
Available indices
| Index | Description | Formula | Image import type | Platform |
|---|---|---|---|---|
| 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) | Drone and satellite. |
| GNDVI - Green Normalized Difference Vegetation Index | NDVI index without red channel availability, for areas sensitive to chlorophyll content. | (nir - green) / (nir + green) | Multispectral | Drone and satellite. |
| 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 | Drone and satellite. |
| 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 | Drone and satellite. |
| 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 | Drone and satellite. |
| NDVI - Normalized Difference Vegetation Index | Generic index used for leaf coverage and plant health. | (nir - red) / (nir + red) | Multispectral | Drone and satellite. |
| SIPI2 - Structure Intensive Pigment Index 2 |
Index used in areas with high variability in canopy structure (e.g. forestry).
|
(nir - green) / (nir - red) | Multispectral | Drone and satellite. |
| 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 | Drone and satellite. |
| VARI - Visible Atmospherically Resistant Index | RGB index for leaf coverage. | min(1; max(-1; (green - red) / (green + red - blue) )) | RGB | Drone and satellite. |
| NDMI - Normalized Difference Moisture Index | NDWI uses the NIR and SWIR bands to monitor changes in water content of leaves. | (nir - swir_1613) / ( nir + swir_1613) | Multispectral | Satellite |
| 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 Available 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 now appears 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 Available bands.
The Operations buttons are described below:
| Operation | Description | Operation | Description |
| ( | open parenthesis | ^ | exponentiation |
| ) | close parenthesis | abs | absolute value |
| * | multiplication | exp | exponential (e^x) |
| + | addition | log | natural logarithm |
| - | subtraction | max | maximum value between two arguments, the separator is ";" (semicolon) |
| / | division | min | minimum value between two arguments, the separator is ";" (semicolon) |
| ; | (semicolon) separator for functions that take more than one parameter | sqrt | square root |
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,
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.
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
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
Hi pix4D users,
Recently I tried to process a thermal image using "ThermoMAP camera" processing option in pix4d. However, constantly getting "generate index failed" error. what can I do to solve this problem. or which processing option is best to process Zenmuse XT2 camera thermal image?
Thank you.
Can you send us your p4d file and logfile? I would recommend unchecking/disabling the indices generation in processing options and then after step 3 is completed, click on index calculator. Do you still get the error?
Hello,
I was wondering would it be possible to calculate soil moisture index using pix4d?
I have both the parrot anafi thermal and parrot bluegrass multispectral UAVs.
Thanks
Hello Abdullah,
Hope you are doing great. Okay from your cameras I see you have the following bands available:
Our suggestion is to try many vegetation indices and choose the ones you think best reflects your crops’ health. This is because it is true that each index has a purpose. However, this varies depending on the crop, soil quality, environmental conditions, etc.
Once you generate the indices which can be generated with the bands available in your cameras (described above). I will recommend doing ground scouting on those stress areas. You will recognize the reason for the stress: nitrogen deficiency, soil moisture, etc.
I would recommend starting with the NDVI index.
Let us know if this helps
Sincerely,