Important: Available once step 1. Initial Processing has been completed, and the Index Calculator Reflectance Map and Index Map have been generated.
With section 4. Color Maps and Prescription it is possible to:
- Change the number of Classes:
By default the number of Classes is set to 5.
The number of Classes is limited between a minimum of 2 to maximum of 32.
- Increase/decrease the number of Classes by pressing on the arrows:
Increase the number of Classes. 
Decrease the number of Classes. - Enter the number of Classes directly:
Input the number (from 2 to 32) with the keyboard. - Select the classifying method from the drop-down list:
There are three ways of splitting the classes, Equal Area and Equal Spacing and Jenks.
By default, the Equal Area method is selected from the drop-down list. - Equal Area
When Equal Area is selected, the classes are defined by the area that each index value interval occupies.
- Equal Spacing
When Equal Spacing is selected, the intervals are divided equally within the min/max range.
- Jenks
When Jenks is selected, intervals are divided using the Jenks natural breaks optimization method. For more information: Wikipedia.
- Enter the minimum and maximum index values to set a range:
The Min/Max values are not the same values as the minimum/maximum values of the reflectance maps. The software will cut off by default the outliers on the edge of the histogram. If the user wants to still use the maximum/minimum value, they can be modified here:
- To display the pixels that have an index value outside the selected range (Min/Max) with the color of the minimum or maximum selected index values, select the Clamped box.
- To display with transparency, the pixels that have an index value outside the selected range (Min/Max), deselect Clamped box is deselected.
- Enter the Prescriptions of each Class:
1. Click Prescription... to open the Prescription pop-up.
2. (optional) For each Class, under the column Comment, type in comments, based on the information acquired from on-site scouting. For example, the comments can be based on the plant's health condition based on the notes taken in the field.
3. (optional) For each Class, under the column Rate, type in rate values based on which fertilizer will be applied.
Note: The rate values do have units. The user can define his own application rate depending on the units of the contractor console.
I want to do that with Pix4dfields because when I trim the NDVI it changes the min and max and something that was red is now green.
Lionel Caputo Are you processing inPix4DMapper and then importing the index map to Pix4DFields? Was the NDVI map generated with Pix4DFields? Can you give us some screenshots to better understand?
I'm processing and generating everything in Pix4DFields. What I want is to have the same histogram in both pictures. When I trim the index it will automatically change the histogram min and max values.
Hi Lionel, Thank you for the explanation. The feature for changing the max, min values in the histogram is coming in our next version. I can understand how important this feature could be. For now, I would recommend exporting these maps and using QGIS for setting the max, min values for visualization. Let me know if that answers your question.