Late last year we released our first version NDVI converted cameras using Schott BG3 filters. Using those filters we were able to generate pseudo NDVI images with a single camera, building off the work of the Public Lab project. After working with faculty at the University of Boston and the MEASA Lab at KSU, we determined that we weren’t quite getting the best results possible with the BG3 filter glass. Unfortunately, no off the shelf filter glass seemed to do exactly what we needed, block out red light and allow NIR light to pass instead. Luckily, we were able to find a manufacturer to help us build a custom filter to our specifications, and the results are looking really good! Below are two images, the first taken by a camera with BG3 filter glass and the second taken by a camera with the new custom glass, the difference is clear.
BG3 Filter Glass
Custom Filter Glass
Aside from higher overall values, there is more differentiation and detail in the leaves and a larger difference compared to the non-organic background material. This is especially important for this type of camera. Since these are uncalibrated, pseudo NDVI images, what is really needed most is high differentiation so that comparisons can be made between the majority of plants and potential problem areas. The higher detail available now makes it possible to catch unhealthy plants sooner.
Custom Filter Transmittance vs Wavelength
The new filters will be priced at $39.99 for the filter alone (8.9×7.9mm, fits SX260 and S100 at least, potentially others) and$499.90 for a ready to go converted SX260 with CHDK. It’s a little cold to be doing any crop surveys here in the Northeastern US right now, I actually ended up killing those two plants after taking them outside for just a few seconds! We’ll be out and collecting imagery as soon as anything starts growing and I’ll post updates as they become available.
Comments
I wonder if anyone used red filter instead of blue. There are reasearch notes on Publiclab which tells that there is better contrast between healthy and poor plants when using red filter. Here are some of them
https://publiclab.org/notes/Claytonb/02-08-2016/plant-health-ndvi-r... https://publiclab.org/notes/nedhorning/11-01-2013/why-a-red-filter-... https://publiclab.org/notes/nedhorning/10-30-2013/red-vs-blue-filte...
I am planning to modify S100 för NDVI, any suggestion on red (or blue) filters for S100 ?
Definitely not true that it's useless. It does decrease the accuracy of the mosaic but you'll find that the error imposed is usually not enough to significantly misalign from Google Earth tiles. If you need survey-grade accuracy then there's no replacement for GCPs anyway.
I've read that GPS lag in s100 is over a second which makes it useless. Is that true? Having Images gps tagged by camera is very practical but if lag is too high it makes it unusable. Alternatively they can be tagged afterwards using data from datalog file.
@Bortek The S100 and S110 have noticeably better image quality. Between the two, you'll find the S100 is hard to buy as it's been discontinued. If you can get one, it has a built in GPS which makes post-processing very easy on any platform. If you don't need that, then the 110 is the best option.
Help! I cannot decide between S110 (or S100) and SX260 to be converted and used for NDVI imagery.
Any experience on these two cameras ?
Darius, It depends on what you want, there are prism array cameras available in 2, 3, 4, 5, and 6 sensors, covering from 400-1700nm. Depending on the requirement, flight time, flight speed,, height, area covered, low light/high dynamic range, the plant specifics needed, lenses etc, these UAV cameras for precision Ag can cost from roughly $6K to $110K.
There is absolutely no converted consumer grade camera that can come close to doing what these cameras can.
Here are several trade websites that every one should look over in this forum:
SPIE www.spie.org
AIA www.visiononline.org
EMVA www.emva.org
Steve, it is not one sensor, it is an array of imaging sensors, 5 in this particular configuration. This has the latest sensor on the market, an sCMOS sensor from Fairchild. Right now there is no available technology better than this, off the shelf, on the market. This sensor is 10 years ahead of the sensors used in the Canon and Sony cameras referenced above. Unless you want a custom imaging sensor, which we do?
The sCMOS sensor will trickle down everntually in to the consumer market, well about ten years from now. The companies I am flying this system for are big Ag business, commercial farms, as well R&D. The Pot problem is mostly on these huge commercial Ag farms. They are working with local authorities and national authroities to stem the tide in the Mid-West. I would not want my cows to eat silage with loco weed in it?
This is not for every farmer, however, if the farmer wants truly accurate data, rot, yield, topography, infestations, etc, this camera will do it. We also use the camera to sort and grade food, such as lettuce. Far faster than humans looking for issues with lettuce, tomatoes, etc.
We have also such cameras for kill floor inspection of meat. We can identify E,Coli and other bacterial infections. Currently we are working on a machine vision project that will scan and identify ground meats, such as sausage for foreign matter, like metal wood, paper, cardboard, etc.
My point here is these cameras are not one trick ponies, they work in a multitude of applications and requirements, with very simple changes in the sensor, filters, etc. Yes, the sensors can be changed out for anything, on the market, even InGaAs for SWIR,imaging above 1000nm.
Expensive, yes, can they do the job better than just about anything else on the market, absolutely!! The data you get off of the Canon, Sony, Nikon, GoPro, and other consumer grade cameras is no where near the quality and accuracy of the data that comes from these prism array cameras, not even close.
Wow! That is a lot of money to invest in a sensor where the technology is rapidly changing.
With a full-size sensor converted camera (Sony A7), I'm sure we could easily fly 640 acres in 30 minutes or less as well. The high bandwidth transceiver system, on board processing and storage all sound great! But, I'm guessing the total cost is more in line with the military budgets and not an Ag budget. Again, with the speed of the advancing technology it would be difficult to make any money with such expensive hardware. I'm also unclear of the full benefit gained from using it. Currently, the FAA only allows line-of-sight flights for commercial use. Once 640 acres is flown, you need to land and move to a new take-off location where you can see the aircraft fly the next 640 acres. While moving, you can easily download and process the data during the next flight. There are also options available to have the images downloaded to a laptop or the cloud while flying, if that is needed.
The plastic/fake plants make sense in the military world. Finding a pot plant growing in the corn field won't help a farmer, unless he wants to catch a buzz. Show me something where you pin-pointed a specific weed or insect problem in a real-world scenario, then treated it successfully, and I'd be more interested.
The base 5 Channel camera starts at $33K, then go up from there.
We have done a square mile, 640 acres in 30 minutes, one fly over. We could do it faster, if we had a faster UAV. The camera can handle it. With on board processing and storage, the data is finished before the UAV lands. We have also used a high bandwidth transceiver system, using high gain antennas I designed and built. As the data is processed on board, it is accessed in real time, sent in through the transceiver.
Hyper Spectral is excellent if you are looking for specific things, such as individual species of plants or chemical emissions, such as methane. We did a project recently that detected Pot growing out in vast corn fields.
The plastic plant/fake plant use is really military. You can see that an enemy is using fake camo. This is part of the FOPEN project.
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