Tuesday, December 16, 2008

Ground truthing - Data is only what you make of it.

The ability to record the processes involved grape growing has increased greatly in the last 20 years. The widespread use of computers has given growers and wineries the ability to keep records of anything that concerns viticulture and winemaking. If it can be measured, it can be made available by the power of the internet.

For the grapegrower, using a computer with a web connection, you can access spectral images of your vine vigour, see how much rain has fallen, how much is expected and, if you are set up look at your soil moisture level. The technology is even available to turn on your water by remote control.

In this way you can run a vineyard from an office.
Vigorous grape vine before pruning c.1920
I am sitting in a vineyard as I upload this to the internet. Web based information is powerful, but there is one big drawback... What does the data really mean if you can't see the block?

Spectral imaging.
Spectral imaging, moisture monitoring loggers and automatic weather stations are key technologies that allow predictions to be made about your vineyard. All are extremely useful, but all need to be 'ground truth-ed' to get the best out of the data.

I once saw a vineyard that was watered from an office in Adelaide, when soil moisture reached a certain level, Summer Refill Point, a notification would be produced, the manager would then have the irrigation scheduled by solenoids connected by a radio link. The next time soil moisture reached the refill point it would be irrigated again.

This was an incredibly efficient system, but in reality it was failing. A quick inspection of the vineyard showed the vines had growing tips, the fruit swelled up and the vines had all the traits of being over watered. The refill lines on the computer graph were set too high.

What the vines looked like, what crop load they were carrying, and all the other the visual cues they giving out were going unnoticed. The computer said water, so they were.

Above: The Visitors Centre MEA Automatic Weather Station. This is a highly accurate device for recording weather data like relative humidity, wind speed, direction and temperature. However its data still needs to be ground truth-ed to get the best meaning from it.


It is possible to get the same miscues from automatic weather stations. For example where a station is placed will affect how it reads. If it placed inside a grapevine canopy it will record different data than if it is in open air. A weather station outside of the canopy will record a hotter temperature than one with its sensors shielded from the sun by a layer of leaves. A leaf wetness sensor placed inside the canopy will dry out slower than one placed in the open. So on and so forth. Most of the time this is academic except for when those differences are vital in making vineyard decisions.

The rate at which leaves dry out after rain has a big impact on predicting weather influenced diseases like Downy Mildew. It is possible that a sensor placed inside the canopy will record different data than one in the open. Leaves inside a fully grown canopy will stay wet longer after rain than the sensor may record. Without checking the vineyard you could trust the data alone.

Technology needs to be used in conjunction with visually inspecting vineyards to get the best out of data. The more technology you have, the more important a persons eyes and ears are.

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