| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| cfastie | "How close is this to what you are trying to do? NDVI depends on the difference between two values: the amount of near infrared light (in a parti..." | Read more » | about 10 years ago | |||
| nedhorning | "Hi jdburnett – It sounds like you have quite a nice collection of cameras. It would be great to run some calibration tests with different cameras a..." | Read more » | about 10 years ago | |||
| cfastie | "Ned, From Mary’s scans, you knew the reflectance of your colored targets for every visible and near infrared wavelength. But it looks like you used..." | Read more » | about 10 years ago | |||
| jdburnett | "Ned, thank you for your tremendous effort in this field. I have been following your work here and reviewing Geert Verhoeven's previous research ve..." | Read more » | about 10 years ago | |||
| nedhorning | "Chris - Here are some comments to your first round of questions: How does this apply to dual camera systems, or does it apply only to single camer..." | Read more » | about 10 years ago | |||
| cfastie | "Ned, This approach looks really promising. I was writing a comment about how this fit in with our current way of making NDVI when I realized I did..." | Read more » | about 10 years ago | |||
| funkycbj | "Light is transmitted but it is diffusely scattered past a certain depth, which seems to be ~7mm. The minimum thickness increases with the size of ..." | Read more » | over 10 years ago | |||
| nedhorning | "Thanks for the suggestion. Maybe a teflon sheet is the way to go although I don't have any experience with these. Some of the thin sheets seem tran..." | Read more » | over 10 years ago | |||
| funkycbj | "Krylon extra flat black spray paint is diffuse and spectrally flat across the vis-nir. A small sheet of teflon isn't too expensive and works great ..." | Read more » | over 10 years ago | |||
| nedhorning | "I have been making some progress toward standardized calibration targets. Does anyone viewing this know of a source for inexpensive paints/coatings..." | Read more » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 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 » | over 10 years ago |