MIAMI, Man. – The infrared photo of 2006 lets a farmer see individual seed rows in a field, with each pixel on the computer screen depicting an area as small as one metre in real life.
It’s a far cry from the first infrared scans of the mid-1990s or the satellite images where each pixel is the size of half a football field.
When Carman, Man., photographer Jack McKinnon first started shooting aerial infrared photos in 1977, there was no such thing as scanning images or e-mailing photos to his clients.
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His Hassleblad ELM500 film camera was mounted in the belly of his Cessna plane, so it shot straight down at the centre of a section of land. McKinnon took the large format negative into his darkroom and emerged a few hours later with crystal clear coloured images printed on glossy photographic paper.
When a farmer bought infrared field photos, he received a package of those high quality, crisp prints in the mail. Although tens of thousands of farmers bought the photos, there were no actual field maps or geo-referenced GPS in those days to allow a farmer to match the image to the exact co-ordinates on his field.
Instead, the common practice was to take the aerial infrared photos out to the field during seeding, spraying or harvest. The operator could match up the actual field conditions to the images on the print. This allowed the operator to accurately note wet spots, weed infestations, salinity, eroded knolls, lodging and other factors that might be incorporated into a field management strategy.
By the mid-1990s, it was clear to McKinnon that the infrared photos would be of greater value to his clients if they could be digitalized and layered onto computerized field maps.
While this was a big step forward in utility, it was at the same time a big step backward for image quality.
The computers of the time bore model designations such as 286 and 386. They were slow and did not easily handle large files filled with detailed infrared data. McKinnon had to compromise if he expected to make his photos more useful.
“It would take so long to download a file,” recalled McKinnon. “And if you sent big files, you were sure to crash your client’s computer before it was downloaded. So I had to compromise and scan to four metre pixels on a sq. mile photo.”
McKinnon said the four metre pixel is good for general reconnaissance, acreage measurement and locating larger size problems. But if you zoom in for a close look at a 40 acre field, the square pixels do not give adequate detail.
A pixel is each little square on the screen that is all one colour. If a pixel covers 30 by 30 metres, then all the colour on that pixel will depict only one visual characteristic.
A 30 metre pixel would register about a third of a football field as one colour. That’s OK if you manage football fields. But if you manage nitrogen inputs on a wheat field, it is of no value.
If a pixel is 20 x 20 centimetres, a resolution that is now possible with current technology, then each little square on the screen can depict the differences from one seed row to the next.
“That means that with our previous system, each pixel on your screen showed you a square that is four metres by four metres. We could scan much better, even back 15 years ago, because the information on the print from the Hassleblad was so much more detailed than what you see on the computer. But many of the computer systems of the day were pushed to the limit with a four metre pixel.
“In order to give farmers the best of both worlds at the time, we e-mailed the scanned image for computer use and then we sent the high quality prints through the postal system. That way the client could use the digitalized photo in his management maps, and bring the actual photo print out to the field.”
That worked fine for 12 years. In 2005, McKinnon decided to move to a higher level of resolution. By that time, anyone using computers for field maps was well beyond the 386 stage. The current crop of computers was designed to handle high end graphic packages.
So last year, he began scanning all aerial infrared photos to one metre pixels. Each pixel on the screen now depicts a one meter square on a sq. mile photo.
For farmers searching for clues in their fields, McKinnon said the same Hassleblad negative that gives him one metre pixels on the sq. mile can also be scanned tighter to give a half metre pixel on a quarter section field.
For vegetable growers who may require extreme definition, McKinnon said he can fly low and shoot to create 20 cm pixels on a 40 acre field. A 20 cm image is the same as an eight by eight inch square for each pixel.
McKinnon said the new standard one metre pixels give a farmer more detailed information about what’s happening in each field.
If the fertilizer delivery system is giving too much product to one tower and not enough to another, the photo can pick it up. It can more accurately pinpoint plant nutrition problems, dry areas, wet areas, weed patches or anything else that might affect productivity.
