In this demonstration, we will walk through three key areas
navigating to the viewer, understanding how the data are displayed,
and creating a download for our area of interest.
You can access the viewer anytime at
MRLC.gov/viewer.
By the end of this section,
you will have a clear sense of how to explore NLCD products.
View multiple data sets and retrieve data for your own analysis.
When you first open
the MRLC NLCD viewer, a pop up window appears in the center of the screen,
highlighting recent updates and new features.
I'll go ahead and close this window by selecting the close
button in the upper right corner of the window.
This brings us to the main viewer interface.
You'll notice that the viewer opens with a land cover map already displayed,
giving you an immediate view of NICD data.
From here, you can add additional products as needed.
Along the left hand side of our screen.
You'll see a vertical panel
listing all available NLCD products, including annual NLCD,
annual NLCD summary products
NLCD tree canopy and legacy NLCD.
Below this data set panel, we find our layers panel,
which allows us to turn on and off overlays,
boundaries,
and base layers for ease of viewing.
At the top of this left pane, you can filter products by region,
including the continental US, Puerto Rico,
Hawaii, and Alaska.
Just above that are tabs to open the legend
for the current map display.
And the help page
where you can access additional guidance on the viewers.
Many features.
We will return to our contents tab.
This left panel is where you'll spend most of your time selecting and exploring
data sets.
Double clicking on any product
opens it in a new map frame in the center of my screen.
Each product I open increases the number of map frames,
allowing me to view and compare multiple data
sets at the same time.
On the right hand side of our screen,
you will use the Arrange Windows panel to organize the open map frames.
We are able to open and arrange up
to nine map frames at a time.
As you'll see
when I pan or zoom in on any one map frame.
All other map frames are spatially linked and move in tandem,
allowing for easy side by side comparison.
This setup is especially useful for exploring different areas
before downloading data,
and for comparing multiple products or different time periods.
Within each map window, there are several key tools and features to note.
For ease of demonstration, I will keep only one map frame open
and I will use the Arrange Windows tool
to center my map frame into the center of my screen.
In the upper right corner of the open map frame.
You'll find the Select Date button, which appears as a small calendar icon.
This allows
you to change the year being displayed.
This tool is especially useful when comparing two years
of the same product side by side.
Right next to it is the toggle Map Legend button,
which opens the legend for the current product you are viewing,
so you can see the classification of land cover types
at any time.
Along
the same toolbar, you will find the identified tool
marked with a bold icon.
When this tool is selected,
you can click anywhere on the map to retrieve
pixel level information, including pixel values
associated with the Land Cover class for that location.
This is a quick, easy way to understand the characteristics of a specific area
without downloading the data.
The viewer also includes a zonal histogram plot by county,
which can be found on the toolbar above the map as a bar chart icon.
When you select
this tool, county boundaries appear on the map.
Clicking on a county generates a chart
summarizing the land cover composition for that area.
These results can be displayed in two ways.
In the upper left hand corner, you are able to select area percentage,
which shows the proportion of each land cover type within the county
or square kilometers, which shows the actual area for each class.
By default, the chart generates the land cover information for all years,
but you can adjust the time range using the sliding time
bar located just below the county name.
The resulting charts can be downloaded
as either CSV files or PNG images,
making it easy to save or share your results.
Now we will move
into creating a region of interest and downloading data.
First, I will zoom the map
to my area of interest.
At the top of the active map frame,
I will select the Open Data Download Tool button.
This button is a part
of the Map Frame toolbar and opens the download panel.
On the right hand side of the screen.
In the download panel, you'll see a dropdown
with four options for defining your download area.
These include rectangle,
polygon, GeoJSON, and shapefile.
For this demonstration, I'll be using a shapefile.
When you select the shapefile option,
a pop up window appears with the requirements for your shapefile.
It reminds you that only single part shapefiles are supported and it provides
guidance on the correct format, so your upload will be accepted.
I will close this pop up and upload a single part shapefile from my computer.
To do so, I will select choose file.
Navigate to my shapefile
and select it.
Once I upload
a single part shapefile, another pop up appears
saying that the shapefile has been loaded to the map.
This is letting me know that the upload was successful,
and reminds me to select my polygons and enter an email.
Before submitting the request,
after closing this pop up, I will select the shapefile
boundary on the map.
I will then use the download panel
to select the products I am interested in,
and adjust my years as needed.
In the Download Content section,
you'll see format options including Geotab and GIF.
Note that GIF is not available for all products.
If you select GIF, the viewer will create a time series
animation of the years you've selected.
This is an easy way to generate a shareable
visualization showing land cover change over time.
Once all parameters are set, I will enter a valid email address.
I will select download
in the bottom of the download pane.
At this point, another message appears confirming
that the order was submitted and that your request is being processed.
On the right hand side of our screen.
I am able to open the data download tracker
which shows the status of the order.
The status will first appear as pending
and then move to processing.
When the data are ready, you will receive an email notification
or you can download the data directly from the tracker.
There are a few important limitations to keep in mind when using the viewer.
Regions larger than 250,000km² cannot be downloaded directly through the viewer.
In those cases, you'll need to download the CONUS mosaic,
which is available from the data download page on the MRLC website.
Additionally, delivery of your data request can take up to a few hours,
depending on how many users are using the viewer at the same time.
That concludes our overview of the MRLC NLCD viewer.
If you have any questions after today's webinar or need assistance
using the MRLC tools, here's how you can reach us.