This magazine isn't online, but you can get it on your iPad, Kindle or Android tablet via NextIssue. The article is a pretty basic overview, with examples of using a Rite Wing Zephyr and a hexacopter along with a Canon s100 modified with the IR filter removed. But it's notable that drones are getting this kind of attention in agriculture. 

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Comment by Deon van der Merwe on June 25, 2013 at 3:32pm

Dries, the S100 conversion was done by MaxMax.com. It is a special request item. You have to phone them to get it done. The cost last time around was $925 (camera included). They have a method of internal filter substitution that works well.

Comment by Deon van der Merwe on June 25, 2013 at 3:48pm

Mark, as far as I can tell not owning a Canon SX230, is that the most significant advantage of the S100 over the SX230 is that the S100 has a bigger sensor. Bigger sensor generally = better signal to noise ratio. Other advantages of the S100 include a wider maximum aperture (3.1 vs 2.0), shorter minimum focal length (28 mm vs 24 mm), higher true resolution (the resolution is up-scaled in the SX230), and the S100 is smaller and lighter. For many applications, however, the differences may not be significant. I'd love to see a head-to-head comparison between the two models.

Comment by Anderl on June 28, 2013 at 12:22pm

Incredible information in this thread! @Mark @Kevin, I find your opinions very interesting and enriching. You are doing an amazing work... I'll keep tuned.

Greetings

Anderl


100KM
Comment by keeyen pang on June 28, 2013 at 5:55pm

Hi LanMark, AgPixel will be a great product and can save a lot of time and effort of a farmer or the plantation management to made the right decision at the right time. I hope the program will be available soonest possible at the price everyone can afford.

I'm here in the East Malaysia doing some oil palm plantation aerial mapping. So far we have complete about 10000 Ha of land. I also had bought a MaxMax modify Canon S100 and AgPixel seems like just the program I want.

May be I can capture some aerial image with the camera and test it on your system ? 

Comment by James Dunthorne on October 31, 2013 at 11:59am

Does anyone know how the likes of tetracam are doing the conversion of the blue channel to NIR1? 

Comment by Deon van der Merwe on October 31, 2013 at 12:03pm

Tetracam does a traditional red NDVI, not a blue NDVI.

Comment by James Dunthorne on October 31, 2013 at 12:14pm

To calculate NDVI you are meant to use the Red and NIR channels to do the calc. http://earthobservatory.nasa.gov/Features/MeasuringVegetation/measu.... I thought i understood all this, but its one of them "the more you know, the more you realise you dont know".

There seem to be several types of conversion you can do. Which one is the most helpful?

Comment by Deon van der Merwe on October 31, 2013 at 12:25pm

To produce an NDVI you need at least one visible band and the NIR band. The visible band that is least affected by atmospheric scatter is the red band, which is why it is generally the best band for high altitude aerial photography. Because we fly so low, however, the blue and green bands are useful too. In our experiments the visible bands perform very similarly, but the red band has a slight edge under some circumstances. The quality of the camera and the quality of the conversion are probably more important than the specific visible band you use.

Comment by Deon van der Merwe on October 31, 2013 at 12:48pm

The NIR+G-2B/NIR+G+2B algorithm was actually created by Dan at MaxMax.com. 

I created two related algorithms, one of them has a slight advantage over the MaxMax algorithm in most experiments: (NIR-G-B)/(NIR+G+B)

The algorithm I designed outperforms the MaxMax algorithm because the blue and green bands are strongly correlated with each other, and combining their information usually results in a slightly better dynamic range compared to using the MaxMax algorithm or an NDVI based on a single visible band.

With all that said, however, the difference in performance between the algorithms is usually not significant enough to be a real practical concern.

Comment by James Dunthorne on October 31, 2013 at 1:00pm

I read through the maxmax website and i think i understand it now. Are there any spectral response graphs of these maxmax conversions? I am trying to look for stress in wheat maize rape and peas. Will this converted camera give me the data i need to detect a good NDVI picture? Also, any suggestions on cameras to use. I liked the look of the Canon SX260 as it can be hacked with CHDK and has GPS. Are there any other cameras which are better?

Cheers for your replies btw, i appreciate the help

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