Global Forecast Canopy Height - 2019 Interactive Map

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MarkGraham
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Global Forecast Canopy Height - 2019 Interactive Map

Post by MarkGraham » Tue Sep 07, 2021 12:07 pm

A global forecast canopy height interactive map has been released, it is an experimental version. Canopy heights in meters are returned for 30m x 30m ground areas for anywhere in the world by zooming and clicking on the map. The heights are conservative in areas with the tallest trees, but the tool does definitely identify areas with tall forests of interest.

No downloading of software is required, it can be used in your web browser.

It is a really nice tool.

https://glad.earthengine.app/view/global-forest-canopy-height-2019

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bbeduhn
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by bbeduhn » Wed Sep 08, 2021 8:49 am

Wow! If they're able to add 40 and 50m heights, this would be an awesome aid in searching for tall trees. Even as it is, it's quite detailed. The pixels are about as small as individual canopies. The model uses LiDAR as a basis. Thanks, Mark.

Brian

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BeeEnvironment2020
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by BeeEnvironment2020 » Wed Sep 08, 2021 4:19 pm

Yep! It is a nice tool! Though it would be nice for them to add 40 meters and 50 meters, as that could add a lot more taller forests.

Russ

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Erik Danielsen
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by Erik Danielsen » Sun Sep 12, 2021 3:11 pm

I was hoping that even if it doesn't display heights over 30m, that this would at least suggest which forests are relatively taller or relatively shorter. Unfortunately, at least in the region where I can compare to sites I've measured, I think it may be more influenced by terrain and other issues than accurately reflecting relative canopy heights. In examining sites familiar to me, it's displaying greatest heights mostly on north-facing slopes and reduced heights on south-facing slopes, often indicating distributions of tall trees in different parts of a given site that are the opposite of what can actually be measured. Comparing between different sites is even worse- mediocre woodlots on flat ground with canopies 80-100' tall look "taller" in this tool's view than the 120-140' canopies in Zoar Valley, for example. I look forward to improvements in this kind of technology and its possibilities at this scale, but it's looking a little half-baked at the moment.

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dbhguru
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by dbhguru » Sun Sep 19, 2021 10:38 am

Erik,

I couldn’t agree more. The danger with these gee-whiz tools is that they give a lot of people false impressions. The anount of misinformation flowing thereafter can compromise the value of the tool.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

MarkGraham
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by MarkGraham » Sun Sep 19, 2021 4:15 pm

No one is saying this tool identifies the locally tallest trees, at the present moment (see my original post). I think it is pretty good at identifying forests with trees over 25 meters tall, anywhere in the world, which is valuable in its own right.

I downloaded some LiDAR for the Zoar area (really good 2019 LiDAR for that area), and did a color height map (chm) and then screen grabbed the same area from the canopy height tool. So the forested areas on the tool are definitely represented by dark green, albeit they end around 25 meter canopy versus the tallest trees are around 45 meters per the chm. This tool will be improved over time, this 2019 release is a first pass.

It is really interesting to look through geographic areas you have been through or have interest in (tropical and coastal rain forests, national parks, "your local neighborhood", etc.

Attached are screen grabs of the Zoar LiDAR chm and then satellite/GEDI originated data (tool).
Attachments
zoar.JPG
zoar2.JPG
zoar4.JPG

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Erik Danielsen
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by Erik Danielsen » Sun Sep 19, 2021 8:05 pm

Mark, for identifying forest over 25m in height, it is good. And as your liDAR comparisons illustrate it does a good job at showing relatively higher or lower sections of a canopy within a given fairly level area. I'm certainly not expecting to use it to identify the tallest trees in this region. The issue I'm finding is that it becomes misleading in comparing between different sites- once I realized that known sites with canopies 80-100' tall with max heights to 115' displayed similarly in this tool with sites with canopies 120-130' tall with max heights to 150+', I came to feel that there was limited value in looking through other areas that I had an interest in, as sites with truly taller canopies may not be shown as different from sites with lower canopies (or as noted with opposing north-south slopes, actual relationships between those slopes may be reversed by what appears to be a bias towards portraying north-facing slope canopies as taller). I don't entirely understand why many forest areas with the majority of the canopy over 30m show few or no individual tiles to 30m, the tallest usually only to 27m, in this tool. Obviously those 120-130' forests are well above the maximum threshhold, but they're being displayed as 22-27m. I imagine this may reflect limitations in the data or the way the data was analyzed, and I look forward to improvements in either of these areas that may improve the results.

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dbhguru
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by dbhguru » Mon Sep 20, 2021 8:12 am

Mark, Erik,

I don't want to sound overly dismissive of this canopy height tool. But I just applied it to an area in MTSF where the white pine canopy height is between 40 and 45 meters. Maximum tree height is 50.5 meters, but that is only one tree. However, the surrounding trees are, at a minimum, 40 meters, and most are above 42.7 meters. For lat 42.63886, lon -72.93013, canopy height is listed as 19 meters. What am I missing?

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

MarkGraham
Posts: 110
Joined: Mon Feb 15, 2016 10:19 pm

Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by MarkGraham » Mon Sep 20, 2021 8:33 am

Bob, Erik, Bee, Brian

I agree, this canopy capping is an issue. Some kind of regional average must be in use to cap allowable canopy height, even if GEDI and/or Landsat returns suggest a higher local canopy. It's tough to find an email to provide feedback, the best I can come up with is LPDAAC@usgs.gov. I have shared the Zoar example with a couple GEDI affiliated contacts I have.

Mark

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dbhguru
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Re: Global Forecast Canopy Height - 2019 Interactive Map

Post by dbhguru » Mon Sep 20, 2021 9:53 am

Mark,

I remain interested. The reason I kind of jumped the gun is that I frequently deal with government officials and academics here in the Northeast who are inclined to substitute sophisticated software systems for on-the-ground measurements. Integrating the two is an on-going project of mine. I'll give some examples in a future post.

Nonetheless, thanks for alerting us to this tool.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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