|Supported Sensors||Visual (RGB), BGNIR, RGNIR, Micasense, Sequoia|
|Supported Resolution||5 cm/pixel or less|
|Estimated Processing Time||6-12 hours depending on survey size|
The Field Uniformity Tool makes it possible to quantify plot-level statistics on Vegetation Indices. A grid with your choice of resolution is built across the area of interest to be used in the calculation of various statistics. First all available vegetation indices for the data set are calculated. For each applied vegetation indices it calculates the mean and standard deviation for the grid cell. Ideally you would set the grid to 2-3 meters for a sort of generalization of the vegetation index data.
The outputs of the Field Uniformity tool come in Shapefile and KML formats. Currently these outputs are not viewable in the PrecisionMapper viewer so they will need to be taken to a GIS or Remote Sensing software for further analysis. For further instruction on how to open the shapefile version in QGIS software visit our see our Visualizing Your Data section below.
Within your KML and Shapefile outputs you will see a layer for each Algorithm statistic combination.
- Input- RGB Orthomosaic
- Output Layers in KML and Shapefile format-
- SURVEYNAME_Grid_NGRDI (Visual NDVI)
Within each of these outputs there will be fields for various statistics of each grid cell. These include Minimum, Maximum, Mean, and Standard Deviation.
The example mentioned above is for a RGB orthomosaic with Field Uniformity tool. For Multispectral surveys you will have a slightly different set of Vegetation Indices that are used in this calculation-
BGNIR- ENDVI, GNDVI, GDVI, GSAVI
Field Uniformity for Automated Farm Equipment
Many users choose the Field Uniformity Tool for application in Variable Rate Fertilizer equipment. With the right choice of Vegetation Index users can input the generalized Field Uniformity outputs into this automated equipment for application.
If you plan to use Field Uniformity for this use case, note that it is highly suggested to use GCP's for increased geospatial accuracy of your data. It also depends on the tolerance level of the machine over your area of interest. If the tolerance level is about 3 meters or more then it is not as necessary for super precise data collection. If it is a very small tolerance then it increases the need for GCP's.
It is also important to validate the Vegetation Index data on the ground before using in a Variable Rate application. There are many environmental factors that can change the values of the Vegetation Index through your area of interest. You want to be sure that the Field Uniformity output is truly representing the health of the plant before basing a fertilizer application on this data.
Visualizing Your Data
The most functional format of the Field Uniformity output is the Shapefile. With some knowledge of a Remote Sensing or GIS software you are able to open and customize this output for your own use. Here we will discuss how to open the shapefile in a free GIS software called QGIS. We will also explore ways to colorize this shapefile output in the QGIS software. To download this software for free on your computer visit this link- https://download.qgis.org/
1. To open your Shapefile in QGIS unzip your dataset use the "Add Vector Layer" button from the QGIS Layers Toolbar. Choose the SHP format of your output and it should appear in your QGIS data viewing panel.
2. Every shapefile layer has a "Attribute Table" that holds data on each geospatial feature in your shapefile within a table. With the Field uniformity tool the Attribute Table will have a single column showing statistics (Min, Max, Standard Deviation or Mean) based on each grid cell of your shapefile.
To open the shapefile Attribute Table right click on the layer within the "Layers Panel" and select "Attribute Table"
3. You probably noticed that when the shapefile comes into QGIS all grid cells are the same color. Here we will discuss how to colorize the grid cells based on the Attribute Table values. If done correctly you are able to change the coloration of your Grid so that a range of colors represents specific values from this Attribute Table.
To do this right click on the Layer again from the Layers Panel and select "Properties"
4. Under the "Style" section of this screen there are options to change the coloration of your layer in many ways. First at the top of this style section select "Graduated".
5. Once this is done there will be a field called "Column" at the top of the menu. This should be set to the corresponding Column in the attribute table that you will colorize the map around. Lower on the list there is a "Color Ramp" field. This defines the color gradient that will represent these values once the changes are applied.
6. Before Applying your settings to the layer use the "Classify" button to categorize the values of your attribute table across the color gradient.
7. When you are happy with all the classification settings of the layer click "Apply" on the Properties window to see the new colorization of the data on screen.