Petiole FAQ

Newly installed the petiole application to determine the leaf area. I have a problem to calibrate the camera. How should do to calibrate the camera?

To calibrate the camera, you need a calibration pad with chessboard squares. Here is a link to download and print it out using white paper: http://bit.ly/2jHhHps
One square must have a size  10 x 10 mm.

“Does your application give useful data to people who don’t have big agriculture backgrounds? What about people who are not agronomists—the people who just fly drones as a service and want to provide the data to farmers? What can your app tell them by calculating leaf size?
I think you have a really cool product here but there seems to be missing a component that “tells” you what the size of the leaf means. Cross-referencing that with the NDVI map could be a really cool tool but I’m unsure of how it would work.”

We will use a simple example to show how Petiole works. Let’s imagine a woman. Every day she makes a selfie. After 5 days if you compare her selfies – you will see the same woman but she will be completely different. Her look depends on a brightness of a light, flash, makeup, and even her mood (probably, this is the most important factor :)). So in order to understand what changes has happened during these 5 days, you need to equalize these parameters and adjust to a common basis. The same is regarding fields and NDVIs. There are too many factors which influence on aerial imagery: the time of a day, cloud amount, solar weather, shades, etc. So comparing images made in different days we can see the same field and crops. But in every moment field is not the same. So what constant can we use to understand the changes? Leaf surface area & chlorophyll is a small basis, which we can use. And Petiole provides this information. Moreover, we need to measure only control points with the worst forecast for yield, not the every plant in the field. Having a GPS-link to a particular bunch of plants, we can measure the same plants every time and monitor their reaction to our actions (using plant growth promoters, pesticides or any other staff) and their growth.

“… your app would probably have to really give leaf analytics for it to be of more value to us. Like actually telling you something about the status of the leaf. Not just shape and size. How do you provide chlorophyll readings?”

We provide chlorophyll readings through a dark green color index (DGCI). With color calibration on the go and recalculation (from DGCI to Chlorophyll) using our formulas for different plants. With app, you can double check your NDVI with ground truth.

“The app shows me an OpenCV error (OpenCv was not initialised correctly. Application will be shut down) when I press the calibration button. I have installed the opencv manager and other app using OpenCV work well on my phone.”

Please, try to use the last version of the Petiole application. If it will not work – delete the application completely and re-install it.  Also, try to update or re-insall OpenCV manager. We have experienced some cases when this method had worked fine.

“Can data be stored in a file which can be imported into spreadsheet or statistics software on the PC?”

As for storage of data and further usage – we do this via cloud service and yes, you can share this information via email and social media. It is available for our paid customers.

“Is there a possibility to exclude petioles from leaf area measurement? Can also leaf dimensions (length, width) be measured by Petiole?
This would be perfect for determining allometric relations.”

These options are included in the latest release of the paid version.