| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| Thorsten | "Ned, thanks! Confusion is good in most cases! :-) I think I'll give it a try and report. For such a setup do you propose the filters you used (bl..." | Read more » | about 11 years ago | |||
| cfastie | "This is really good information. Another thing that might make red filters a good choice is that it is easier to make a red filter than an infrablu..." | Read more » | about 11 years ago | |||
| nedhorning | "Hi Thorsten, Sorry for the confusion. Some of the non-linearity between the response of the red and blue filter should be explained in the post I d..." | Read more » | about 11 years ago | |||
| Thorsten | "Dear Ned et al., I am pretty new to all this and on my way to convert my camera for NDVI mapping. After reading this post I am little confused: bl..." | Read more » | about 11 years ago | |||
| mathew | "This is great, Ned-- thanks for illustrating it with your examples. The stark difference between NDVI of dead grass in the red channel is a pretty..." | Read more » | about 11 years ago | |||
| nedhorning | "One drawback of using the red filter is that the red part of the bayer filter passes more NIR than the blue or green parts. I'm looking into ways t..." | Read more » | about 11 years ago | |||
| patcoyle | "Interesting work. Thanks Ned. " | Read more » | about 11 years ago | |||
| warren | "Wow, this is an exciting development. I had wondered about using red instead of blue, but your results are compelling. I also wonder if this would ..." | Read more » | about 11 years ago | |||
| funkycbj | "You want to capture enough spectral variation between different surface features. If you only have 2 bands but have several classes then you may ge..." | Read more » | about 11 years ago | |||
| nedhorning | "I'm curious why you need at least 3 bands for automated classification. I don't have a specific classification task in mind. In general I'm working..." | Read more » | about 11 years ago | |||
| funkycbj | "If you take pictures at higher angles (more perpendicular and less oblique) you may achieve a more Lambertian response. Dealing more directly with ..." | Read more » | about 11 years ago | |||
| nedhorning | "That's a good observation. The hotspot in these test images would tend to be toward the bottom around the shadow from Chris' head since that's wher..." | Read more » | about 11 years ago | |||
| funkycbj | "I noticed that you are capturing your test images from an oblique angle. Bidirectional reflectance at that angle may be creating "hot spots" in you..." | Read more » | about 11 years ago | |||
| nedhorning | "If it's sunny tomorrow I'll be out with the wood, tar paper and other things. With a little luck I'll have a research note before the end of the we..." | Read more » | about 11 years ago | |||
| cfastie | "That's a much better filter for the job: It would be great to try some before all the greenery disappears. " | Read more » | about 11 years ago | |||
| nedhorning | "I got a 3" x 3" Wratten 25A gel filter on ebay for $10. There's a lot left over if you want to try it. " | Read more » | about 11 years ago | |||
| cfastie | "Oh yeah, I forgot I actually measured that, and you're right a little more NIR gets into the blue channel (I used a 735nm cutoff filter). I need to..." | Read more » | about 11 years ago | |||
| nedhorning | "Chris - It's interesting that you find that the Canon Powershots don't record much NIR in the blue channel. I found just the opposite - that the bl..." | Read more » | about 11 years ago | |||
| cfastie | "I am confused about the idea of using a red filter instead of blue in a one camera NDVI system. Is the idea to use the red channel for visible ligh..." | Read more » | about 11 years ago | |||
| nedhorning | "Thanks for your comments. I am rethinking the idea that a blue filter is sensitive to chlorophyll absorption. Blue wavelengths have similar reflect..." | Read more » | about 11 years ago | |||
| funkycbj | "A blue filter should be an acceptable alternative to a red filter when measuring vegetation if the spectral response of the blue filter is sensitiv..." | Read more » | about 11 years ago | |||
| nedhorning | "Thanks for the comments Chris. I would be a little cautious drawing more than very broad conclusions at this point. The reflectance values for the ..." | Read more » | about 11 years ago | |||
| cfastie | "Ned, This is really good data. The primary result seems to be that the calibration procedure works incredibly well. Similar NDVI results are produ..." | Read more » | about 11 years ago | |||
| ikerluna | "Thanks a lot for your help I will try to use the same webcam that u are using. " | Read more » | about 11 years ago |