Water Sensitive Paper Analysis
Introduction
Since my first work on spraying assesment, water sensitive paper (WSP) was recomended as a good tool. Althoug is not as precise as magnesium oxide samples or flourescence pigment quantification, it is so much easier to use, that it became a de facto standard on the industry.
I had dealt with several thousand of samples using a free tool available on UT Health. As I have been trying to use Python as a tool to analyse some questions on pesticide application. So, why not to use Scikit Image , based on a tutorial that I found on https://www.analyticsvidhya.com/blog/2014/12/image-processing-python-basics/ that help us to count stars on telescope photos. Droplet impression on WSP cards are not so diferent from a “starry, starry night”
If you prefer to use some more ready to use solution, try Snap Card application produced by Government of West Australia that you can find on Play Store
First things first
I’ve build a dataset from http://sprayers101.com/water-sensitive-paper-for-assessing-spray-coverage/ using different spray pressures and nozzle diameters and I am loading it. Lets’ render one of the images
And now let’s take a different look at it using Skimage blob detection
Number of droplets counted : 325
Medium radius : 1.23781574127
These are the two parameters that we will use to create a dataframe of all the images. Let’s refactor the code, creating a function that we will use in each image iteration.
We will now create a Pandas Dataframe that we will use to analyse and plot the results
We can get a small performance improvement using job parallelization.
As I told you, WSP is not very good to access diameter. Nevertheless, we can a spot a trend in which diameter gets higher with coarser nozzles.
When we try to analyse droplet number, it gets much better. We get less droplet with coarser nozzles…
… and more droplets with higher pressures.
Conclusion
After some stories about pesticide application, I’ve decided to write some about WSP. I will do it again next time, addressing spray coverage quality analysis.
