Accessing 3DEP Lidar and DEMs / WBD Improvements in New Hampshire

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  • 00:05 Accessing 3DEP Lidar and DEMs: Presenters - Rob Dollison & Jason Stoker
  • 16:21 WBD Improvements for White Mountains National Forest, New Hampshire: Presenter- Brittany Gold: USGS Utah Water Science Center



Date Taken:

Length: 00:45:14

Location Taken: Reston, VA, US


Um? Today the first topic we have  is talking about how to get access to and how to how to get. The LIDAR data 3DEP data from from our website and we happen to have a recording of a video that Rob Dollison and Jason Stoker recorded a month or two ago. This was earlier this month and that goes through it in kind of has a pretty good presentation of that, so we're going to play that video. Hopefully that will work for us here. We just tested it a few minutes ago and finally got it to work, so will play that video. It's 15 minutes long and then will have Jason on to answer questions for about 10 minutes or so after that and then after that we've got Brittany Gold who will talk about the WBD. Uh, in I believe it's a White Mountains of. Is that New Hampshire Vermont? I've forgotten here.  >>New Hampshire and Maine.  >>New Hampshire and Maine OK, thank you Brittany. Alright, so let's start this video. Good afternoon, we're here today to talk to you about the National Geospatial program and how to access the 3DEP lidar and DEMs. To help with your coastal studies. Our goal today is make sure you know how to access the 3DEP LIDAR data and DEMs through our USGS national map data delivery and Services Web page and will also be focusing on the lidar specifically on the lidar Explorer application and accessing data without having to download it. This is our national map Data delivery homepage. From this site you can get to our major applications for accessing data as well as to our MAP services. So we have things broken up into accessing Topo maps, GIS data and on web services. We have over 50 Web Services, 5 which are base Maps. Up here where you can scroll through our major applications and the data download application is our primary one for accessing all of our data for vector and raster data. We have a viewer for exploring our data as well through the services, Lidar Explorer which will dive into and we even have a demonstration viewer for working with our our elevation services, dynamic elevation services, which you can render on the fly. Jason will be going more into this in the future. So right now I will show start off with looking at our National Map Downloader, give you an idea of what the experience is like here. I'll zoom into Chicago. Alright, we will be looking at for our case. In this case the source elevation data are LIDAR data. We can look at where we have lidar available. In this case I will. Zoom in and select a small area of interest and search for products. See a listing of the lidar tiles and start looking at where those are over at my area of interest. We have access to the metadata and other information on the right, but I can also show all footprints or show all thumbnails. And get a basic idea of the lidar data over this area. From here I can go at it to our cart  or get a CSV listing of all the files to start downloading. Now I want to show you the similar experience using our Lidar Explorer which is optimized more for looking at, Investigating lidar. here I again have zoomed in Chicago. We can see that we have tabs for Lidar, DEMs and another product like our Ifsar products in Alaska that you can look at. But I find it pretty easy right from Lidar to come in here, show where the lidar is available to find my area of interest. And up comes a nice listing of the project - lidar product over this area. I can also get a full listing of the DEMs available. As well as the lidar over that area. But one of the key functions here that is different from from our generic downloaders I can come in here and you can see this green dot. Right and this enables me  to come in says this state has been processed where I can visualize it in the cloud. In this case, we're launching it into Potree Viewer. And I can zoom in. Let's say the Chicago my areas and start looking at the actual data. Before I start to download. you can even do some processing and working with this data in this viewer. So there's a series of quite a few tools available. In addition to things such as filtering which you will see down here filters and a variety of other things, I'll quickly just show. A tool such as a measurement tool that's available here. Just to give you a quick idea of how you can explore the data right through the web browser. And you're working with millions of Points of lidar that you can manipulate. And and work with even before you decide to download it. So another key component in the Lidar Explorer is still more in the research area, but we are starting to have more ability to start to process the data in the cloud, and so in this case you might offer first returns and some processing it, so it's a more limited capability to experiment with it. I expect this area to grow and Jason will be taking over the presentation here to talk to us about how we how to work with the entwined point data format up in the cloud. Jason, you wanna take it  over?  >>Sure thanks Rob. Hi everybody, in the future and hello to my future self. Hopefully I trimmed my nasty covid beard between when I'm speaking to you now and when will be talking to each other live and in person. So yeah, I'm going to talk about about an hours worth of material and in about 7 minutes. So I'm going to move pretty quickly. Uh, as Rob mentioned the focus and the real power that we're seeing now with our lidar point cloud data has to do with having it enabled in the cloud and particularly in the Amazon public datasets. So Howard Butler has done a great job getting all of our point Cloud data set up in this Entwine point tile format that you can see here, which enables us to tap into these data in the cloud and do some processing. So we're moving kind of away from the download first paradigm to being able to have actionable information extraction in the cloud or via other services like on the DEMS, which I'll show in a minute. So if you come here the you can get to this page. There's some great tutorials on things and as people build things off, this public data set there, they're enabling tutorials and links for you to try out as well. So that's um. That's really exciting access to our data in the public data set. Howard is also built this Entwine viewer that takes all the projects that we have available in the public data set and has organized them in a way so you can come in and do exactly like what Rob showed a minute ago. Click on it and you can view in Potree, for example. So because I don't have a whole lot of time, I'm not going to go into that, but that is available at if you're interested in accessing it this way. The other thing that's really exciting is since this data has been converted into EPT Entwine point tile format, we can apply these scripting tools such as P-dal or 'poodle'. However, you want to say it to take the data from that public data set bucket and run scripts and processing on it and delivered just what you need. As Rob showed, we have a version available in Lidar Explorer that enables you to do some small tweaks and small filtering. And spit out a Pdal script to JSON set of code that runs through the data and you can apply filters. So if you go to the page you can get to this and there's a tutorial specifically for reading data from ept and creating a pipeline using Anaconda. And so I already did that for a small data set here. What I ended up doing is using the tutorial that Howard had has on this page. Modifying it a bit to create my own thing. So I extracted from this project here and these bounding boxes, read the data, and then  just filtered the data that only had classes one and two and then ran a height above ground filter on it so it normalizes the data. To create that before, so everything is measured from the ground points themselves and then spit that out on my desktop right now in  this script, anyway to this LAZ file. And so in the interest of time I'm not going to run that. It took about a minute and a half to do so having a minute and a half just watching processing when you only have 15 minutes total, is too much, so I ran it here and so that you could see this is the result I'm showing in global mapper. But just to give you an idea of how this this script worked here so you can see that it created the height above ground file from that data in the cloud and then delivered that to me so I could render it here and you can see its height above ground because the ground points are all at zero and the non ground points are above that. So as Rob mentioned, you know on that on that Lidar Explorer page it'll generate a Pdal pipeline for you that you can then run using Anaconda like this and. And then there is a little functionality to to run that in the cloud as well. So that's the focus on the point cloud data on. I'm now going to quickly talk about the elevation dynamic elevation service we have, which focuses on creating Service that enables you to tap into our elevation data without having to download it. You can find more information at this page here. And see So what I'm going to highlight is how you get access to this and how do you put this elevation service into ArcGIS. And I'll even show QGIS real quick. so the the link here that. Is important, really doesn't look like much, but if you go up to this WCS link here you can copy this. Location. And then if we pull up ArcGIS. Add GIS server. For some reason you have for ArcMap you have to add it as a ArcGIS server. So I'm going to put that here. And here it is. And so it is going to bring in. That WCS for us. And so as you see it, all the elevation data that we have available is in this mosaic type data set. So where we have 30 meter data is in here where we have 1 meter data. It lays on top of that. So as you zoom in closely, the rendering of it will depend on what data sets we have available. They always put the highest resolution on top. So this is showing Hillshades which are nice, but you know we've been able to to render Hillshades for awhile. The power of the WCS really is the fact that the individual elevation values are there. So what you have to do in order to get to that is once you load the WCS up you go to processing templates. And hit none. And then that will change it to the actual elevation data. So if I were to. I'll just change the color real quick just so we can see. If do you that? Let me do this here so we can see. From the current display extent, so that gives you an idea and you can see that just the values on the scale show you that these are actual elevation data values in meters. So what the power of that is is then. If you have that available and you have, you can tap into that and now you can run. It can run tools in Arc. On this WCS and I'm not going to do it 'cause it again this takes takes awhile to process but I already ran it but for example if you wanted to do curvature you could run curvature on this WCS and then. Have it pop up here and it's tapping into that WCS in in your spitting out the result without having to download all that elevation data yourself. I'm so this is just kind of showing you what curvature would look like for that, so we're hoping you all can take take advantage of that. This this application I think it's going to be useful to more people learn about it. So you can do similar things with the WCS in QGIS. I just wanted to show this really quick. If you are interested you can go to layer, add layer at WCS layer, and then you put that exact same WCS Link in from the web page that I showed and then you can choose the layers that you want to render. In this case I'm rendering elevation. And as you can see, if we zoom in and out, I'm looking at the elevation data. You can tell that it's actual elevation just based on the numbers that are showing up in the legend. So that's So what we wanted to show you in a lightning lightning fashion. >>Next, we've got Brittany Gold, who is on the WBD team and she is going to talk a bit about White Mountains WBD so Britney go ahead and take it away. >>OK, thanks Al so hi everyone, I'm Brittany Gold and I'm part of the WBD national team. I work with Kim Jones, Lily Niknami, Drew Decker, Sheryl Boyack along with many others on national hydrography initiatives and quality control as well as assisting with local projects. And today I'm going to be talking about a recent project to improve the WBD. With acquisition of high Resolution elevation data which that previous talk was great, segue way into this. There's been more interest in deriving high Resolution WBD and NHD from this elevation data. over the past couple of years I've worked with the Forest Service to update that WBD 12 digit hydrologic units and develop HUC 14 and 16's in the White Mountain National Forest in New Hampshire. I'm going to discuss these improvements as well as lessons learned throughout this process. Oh dear, my keyboard is not working to advance the slides. OK, I'll use my mouse OK, the White Mountain National Forest covers over 800,000 acres in Eastern New Hampshire, and western Maine and the boundary of the White Mountain National Forest is shown here in green. It is one of only two national forests in New England and its its landscape is a mix of low lying hardwood forests and mountain mountainous Alpine terrain. Over the past several years lidar has been collected in the forest and one and two meter DMS had been developed by Mosaicking lidar tiles of less than one meter and resampling to create the two meter DEM. This project was an initiative within New Hampshire to update the NHD &WBD and the White Mountain National Forest based on the new LIDAR data and was a cooperative effort among the New Hampshire Geological Survey Department of Environmental Service, the US Forest Service, White Mountain National Forest and the US Geological Survey. Utah Water Science Center. The White Mountain National Forest seen here with that green outline intersects 72 12- digit hydrologic units. These units were updated from one to 24K Topo delineated watersheds to 2 meter lidar derived watersheds using the arc hydro toolbox. Through this project, 316 14-digit hydrologic units were developed using the two meter lidar DEM. In addition, I was tasked with creating a catchment for every densified stream segment. Doing so, create over 100,000 draft HU16's which are currently in the review phase. The Forest Service plans to field verify these HU16's as well as the streams within to verify that it should be included in the NHD. The maximum number of HU16s in this area that could be added back into the WBD is around 32,000 since there can be a maximum of 99 HU16s per HU14s. Due to the hydrologic unit coding for 16 digit watersheds. So the number of HU16s will be need to be parsed down prior to going back into the WBD. This is an example of two updated HU12s on the left outlined in black with newly created HU14 seen by the red divisions nested inside on the right. The hydrography displayed here is the current NHD just for visualization purposes, not the draft hydrography. And this illustrates the smaller HU14 subdivisions in the HU12. This is the same couple of HU12 on the on the left. With those HU14s inside and then on the right, the orange lines represent the newly created HU16s and we can see all of the really small in their catchment size. Draft HU16. So now I will take a look at the hydrography. The current NHD is an image on the left here and on the right is the draft hydrography in the White Mountain National Forest, which is much more densified. The Forest Service plans to field verify these by HU12s and remove any flow line that does not correspond to a stream on the ground. The Forest Service ask for a watershed for every segment of flowline and they plan to field verify these by HU12. So they're going to verify all of these. HU16 by HU12, and they're going to remove any HU16s that either contain intermittent stream or do not correspond to a stream on the ground. These HU16s will help with forest management, including timber sales and assessment, as well as erosion and other small scale landscape changes. And this is just a closer look at those HU16, so you can really see the level of detail here with us streams of HU16 for every single stream segment, so more of a catchment size data set. So as a byproduct of updating HU12s , the boundaries at larger scales are also updated, such as the HU4 boundaries seen here. Here the Purple Line is the old boundary and the black line is the lidar derived updated boundary, and we can see a great much greater detail in this revised boundary. In addition, using the two meter DEM also allows for greater detail, and we can actually see that these stream segments over here blow to the Northeast instead of as their previous as the WBD this previously delineated, they were flowing down into this Charles River HUC 12. So this allows for further updating and refinement of the watersheds at all scales. As you can imagine, working a project like this for the first time, especially developing HU16s and HU14s from scratch, I've quite a few lessons learned that I'd like to pass along for those of you working on a similar project or starting to develop a similar project. The main challenge I faced was working with the draft hydrography. The archive process that we typically follow includes bringing the hydrography into the Dem, using hydrography that hasn't been QC'd creates issues in waterbodies. Doubleline streams, culverts and snapping to outlets. These all have major impacts on catchments that are derived with hydrography in DEMs. This image includes the dropped hydrography and Blue HU14s in Red HU12s in black. And this highlights some of the issues with the draft hydrography in the Lake and in other areas. So we can see that the the draft hydrography just flow straight here instead of following some natural topography. Also through the Lake is just cutting straight across instead of like QC'd NHD that would include like an artificial path through here. So one of the main issues I faced was the lack of culverts included in the hydrography and the absence of a culvert data set. Either of these would greatly improve the accuracy and ease of watersheds derived from the elevation and hydrography. Since the draft hydrography did not include many culverts, I created a culvert data set with any major missed culverts that would affect the watershed delineations and I provided that back to New Hampshire so it could be included in the refined hydrography. The state is currently working to create a comprehensive field, verified culvert data set, but should be very useful when they create their revised QC'd hydrography. So I'll go through several examples where these missing culverts would have impacted the outlet location as well as areas that are included in the HU14s and HU12s in this example on the following examples the culvert will be circled in purple. The draft hydrography in blue, and the WB boundaries for the HU14s in Red and HU12s in black. In this example, the hydrography diverges to the East at the road instead of continuing through these culverts here. And then if we take a look at the Dems, there are two visible culverts and we can make out the channels at this scale here.It's a little trick up here at this scale and then also using the NHD which is in light blue here that really was able to guide my eyes towards areas with potential issues in the draft hydrography. A similar issue can be seen here, where the draft hydrography diverges West at the road. There's a Clear Channel on either side of the road and we can even make that out on this imagery at this scale, and there's not a channel heading to the West of this road. And then if we look at the DEM its a little tricky to see at this scale, but you definitely don't see a channel heading this direction. And then if we zoom in super tight here, we can see a channel on either side of the road which would indicate that the hydrography should be routed to the North instead of heading West along the road. And then here's another similar issue with a very Clear Channel on either side of the DEM. Are outside of the road in the DEM, sorry. And then if we take a look with the imagery you can see Clear Channel the the hydrography should be flowing under the road. Here is indicated by the NHD and we can even make out the Culvert at this scale. Looking at this imagery. The absence of culverts included in hydrography in culverts burned into the Dems will not only affect outlet locations but will also affect catchments that are included in watersheds. When running the ArcHydro process. In this image, a large portion of this Johns River unit would have been excluded from the watershed without intervention. Since there are couple of missing culverts. We can see that this draft type geography in the South does not connect to the flow lines in the North in the Johns River unit. While there are two visible culverts. And the NHD also indicates that there is flow from the South to the North. Here instead of due West, like the draft hydrography has. Similar to the previous example, missing culverts in the hydrography impact the size of the unit by excluding or including tributaries that are connected to the main stems by culverts. In this image, the southern portion of the unit would not have been included in the Rattlesnake Mountain Baker River, HU14 without the Culvert. So you can see all of these flow lines connecting up here and then flowing to the East, whereas there's a culvert right here that would indicate that they should be routed to the North, and if we look closely at that area. We can see this channel here which we should have routed by hydrography through instead of heading due East. This is another lesson learned on importance of QC'd hydrography as an input for generating accurate watersheds. If HU14s were generated using Arc hydro process without comparison to the previous hydrologic units than the entire northern portion of the Upper Ellis River HUC 14 would have been included with with this adjacent Peabody River Huc 14. So they draft hydrography, has the flow lines routed here directly to the East, and so everything North of this purple line would have been lumped with this other HU14. But if we take a look at the Dem. There's actually a Valley here that indicates that the flow line should flow to the South here, and if we zoom in really tight there an add some contours. We can see that there is a valley through here and that this draft hydrography crosses this small divide, and NHD also helps illuminate this. Even in areas that are not heavily urbanized, humans still have an impact on the landscape.  and on the hydrography. accurate culvert locations are very important, especially when creating densified hydrography and catchments. Either the inclusion of culverts in the hydrography or at a minimum, a culvert data set that could be used to burn into the Dems alongside the hydrography would have improved this process. A culvert data set would also be helpful prior to creating the hydrography. But if there are not culverts in the hydrography, there are processes that can be used to help identify them, and Al Rea has discussed subtracting a field DEM from a raw DEM to help highlight culverts, and this could have been done prior to generating catchments to highlight locations that have been filled and where culverts may be. My colleague developed a tool using this process and outputs are seen here in pink. Pink areas Highlight potential channels on either side of the road indicating a possible culvert. And we plan to use this tool to help QC elevation derived WBD in the future, especially with the upcoming EDH projects. After running the arc hydro process with the draft hydrography and reviewing and at times manually updating the generated watersheds, there are a few things I would have done differently. I likely would have tried to run the watersheds without burning in the draft hydrography. And then intersected the generated watershed boundaries with the draft hydrography to look for potential conflicts that way. I also would have used the existing NHD and draft hydrography to generate culverts and burn those into the Dems. Another way to approach your project like this with draft hydrography would have been to burn in the existing NHD, generate catchments and then intersect the draft hydrography with the watersheds to look for conflicts that way. With the absence of QC'd hydrography following these processes would have created purely elevation derived watersheds without the influence of some of the strange strange hydrography artifacts and would have eliminated the need for as much manual intervention and review. Through this process I was able to provide some level of QC'd , hydrography and culverts back to New Hampshire for when they have the capacity to update and still verify the hydrography. This process really solidified the importance of using QC'd hydrography at that's going to be an input in your watershed creation process. QC'd hydrography, alleviates issues caused by different flow past due to anthropogenic influence. It also helps with accurate outlet locations for the watershed since the WBD outlets are there snap to. NHD flowlines for single line streams or cut perpendicular across NHD area. For double line streams. Since the hydrography was not always in the channel of outlets, I use my best judgment to find the center of the channel and create a WBD boundary that the NHD could be snapped too. Through many iterations of my partners in the Forest Service, we were able to create an accurate and WBD compliant HU14 data set based on the 2 meter LIDAR. I just heard from the New Hampshire Department of Environmental Services that field Checked lidar derived flow lines for one HU12 will undergo Geoconflation and will soon be back in the national NHD. This may impact the WBD outlets which will then in turn be reviewed. NHD and WBD updates are sometimes an iterative process. As a steward or a partner makes changes to one data set based on better data than a corresponding change in the other data set is often necessary. Thank you any questions. >>Yeah, great thanks Brittany. So folks, if you have questions, I think the chat has been the best way to do that. Go ahead and type type your questions there into the chat so there's a couple of questions in there already. Britney. Can you see them or you want me to read them to you? >>I can see them. So the first question about why the Forest Service needs that the HU16s? Not totally sure in the specifics, that was just part of our contract, but one of the understanding was for timber sale assessments. They have a lot of interest in that in those areas, and so they want to assess the downstream implications. when there's timber sales. But I can definitely ask my contact in the Forest Service and follow up with you, if you would like Jane? The second question about the the delineation method. I don't know the answer to that We have a process with Arc Hydro that the WBD team in my office uses and. I am not sure which one we use, but I can look at it and let you know. So OK, so how many 14? OK, but she clarified the question. So how do we decide how many HU14s the (inaudible)  were divided into? So the first step we did was to look for the major named streams, Brooks and Creeks within the HU12. And then created them based on like. On that as well as working with my Forest Service partner to see what made really made the most sense with the hydrography in those areas. And through that we actually ended up breaking out a few different HU12 that were these longer. River is that were lumped in with an existing HU12. >>Brittany, this is Sean Vonn from Minnesota. Can I add to my comment in the chat there about burning streams into the DEMS? >> yes. >>I think first of all I'm very well versed in the subject matter and been advocating for well over a decade on how best to derive hydrography from LIDAR and and have done a tremendous amount of burning in. Water courses we did that in the old days of working with 30 meter DEMS and I always want to caution folks in from a national when we're reaching out at a national level that. Burning in is in. I'm sure you know this. It's really kind of a band aid approach, but it. I understand it buys time, but it leads others to to do that and we really need to be progressive and how we strategize on working more intuitively with lidar drived products and really thinking harder about What what's lacking in our vector line data and how can we improve it by working with the DEM instead of burning in old problems into a very new product and especially when talking about one meter DEMS and even better with coming from high density lidar. I'm really fearful that advocating that from at a national scale will lead others to do that, and that's what the comment is about and I'll stop there. Thank you. >>Yeah, I definitely understand that and the from The WBD perspective typically will burn in the NHD when it's QC'd and checked and we know that we're burning in good data and so that helps with our outlet locations as well as like making sure that we are including what we intend to in the different watersheds. But I definitely understand, especially something like this where burning in the the draft hydrography that wasn't. Of Super High Standard creates all kinds of issues, so just that's why I think if I were to read on this project I wouldn't have used the hydrography to begin with >>And Brittany, this is Drew. So you're saying that the corrected data wasn't available anyway for this particular project.? >>right >>Yeah, and and this Al I just you know I want everybody to understand we're not on a national basis  talking about burning in existing NHD. What we are talking about doing and what we've been experimenting with is what we're calling elevation derived hydro. I've seen a couple of references today to EleHydro that's that's that's the old name that we were calling the similar idea, but the idea basically being that we should be using the 1 meter or the high resolution LIDAR data as much as possible. And but but, as Britney pointed out, you know there's there's big problems with just taking that in a raw sense.  you need to know, especially where all of culverts are. And so I think. Existing NHD can be helpful in that regard and in the work that we've been doing with EDH, we've been using the existing NHD as a guide and trying to make sure that all those features are represented, but with the understanding that elevation data is really still the key, and that's what should be driving our feature Hydrography development is is at high resolution LIDAR data. Let's see. Tracy made a point about sort of the iterative aspect of first editing NHD & WBD and then having maybe go back, you know and forth and he's wondering about if there's a way to do this together. Do you have any thoughts on that, Brittany? >>Um? Not, I mean. Right now there really isn't a way to do it together since the NHD and WBD checkout processes are separate. I don't. I don't know if there's discussions about combining them in the future, I think that would be a big modeling and tools change, so unfortunately I don't think so. I mean, one thing that could help would be to if you're a steward on or an editor for NHD and WBD, then you could likely avoid the back and forth a little bit between the two checkouts and datasets, but. Right now I think you know the best thing is to  Try to handle any possible issues that you might introduce in the other data set before you make this change or or just understand that you'll have to change the other data set and correspond. And there's also the markup tool that can help if you're not an editor in both datasets, and you can submit markups and that helps to keep both of them current and up-to-date and clean. >>OK, and yeah, there have been several comments regarding  a national culvert database, and Yeah, I'd love to see it. I'm not sure were we're. We're not quite sure how to go about doing that. At this point. One way to do it would be as we're calling addressed data or use the older jargon you know, indexed or event data based on on the NHD. Um, but that's still kind of ongoing. We're we're looking into it, but. We're not sure we have the resources to tackle that ourselves. But you know, we're. Looking at that sort of thing. And yeah, this this basic idea that we've got with I think I've talked on this call before called the National Hydrography Infrastructure, which is sharing, a way to share reference datasets or address datasets based off of the NHD is really kind of what we think might be the best way going forward, and that's that's where we're not building a single centralized database, but we make it easy for people to share their event data if you will. In, in in, sort of a structure that that everybody can share their data through web services similar to the services that Jason showed earlier, right? Once you have things out in a web service and it's described consistently in everything that we can. Do a whole lot of work you know pulling those in instead of Trying to maintain a centralized database. Gosh, we're running short of time. Brittany, did you see anything more in the comments or questions that you wanted to address? >>I think this will ease kind of answer. Some of the questions going through the comments. One thing that Greg just kind of asked or stated or wanted to confirm was that the. That the hydrography is was the lidar derived hydrography, but it was a draft version, so it was not QC'd yet and it has not been field verified. But that is the intention of the Forest Service in the state will field field verify that prior to submitting it back into the NHD, and they've done that for one HU12. But I think that the level of effort might be a few years before they get all the hydrography there field verified. >>Oh Right. Oh, I think we may just. Barely have time to address the one another question about wide rivers. I think those Jim's question about wide rivers that might have water surface elevations that varies from reach to reach. Yeah, that's a problem. Even with you know this highest resolution Lidar data. The lidar collections may have been done at different times, so you have different water levels and that's a challenge, and it's not just in rivers, but lakes too. Quite often with reservoirs, you know, maybe the lidar was phone when the water was really low. And the water body doesn't look like the what we would have in NHD, which would be sort of a normal pool elevation. So that's something we're kind of struggling with right now. Don't have any good answers yet. Um? I want to try and be respectful of everybody's time, so we will go ahead and cut this off here. I'll leave the chat going. I'll leave the meeting going in the chat here for just a couple more minutes. But thanks again for everybody coming and we will have the recording up on our YouTube channel pretty soon and we'll see you all next month. Thanks again.