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How to Overlay Grids Using the Combine Function in ArcMap - LANDFIRE Help - YouTube
Channel: LANDFIREvideo
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This video demonstrates how to overlay two
grids using the Combine function in
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ArcMap.
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In this example, I will be overlaying the LANDFIRE Biophysical Setting (BpS) grid
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with the LANDFIRE Succession Class (S-Class) grid.
I'll be working in ArcGIS
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10 but a similar process can be used in
other versions of Arc.
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The first step is to open
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Spatial Analyst tools in the toolbox
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then select the Local menu and
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the Combine function. To perform the
combine, simply drag and drop the grids
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into the dialog box.
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The Combine function will add the Value
field from the input grids
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to a new grid attribute table in the
order in which they are specified here.
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So, I'll add the BpS grid first
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and the S-Class grid second, because
S-Class
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is an attribute of BpS and should
therefore appear after it
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in the new grid attribute table. Check
to make sure that the new grid will be
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written to the right workspace
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and then click Okay. At the bottom of the
screen
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you will see a message when the Combine
command begins working.
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When it is complete the new grid is
added to the project table of contents.
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Here's the new combined grid.
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Opening the Attribute Table you can see
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that both the BpS and S-Class value fields
from the original grids have been added
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to the new grid.
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Notice that none of the other attributes from the input grids are present.
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if you want to know what BpS 759
represents, for example,
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you would have to open the original
Attribute Table from the BpS grid.
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That's inconvenient, so let's join in
the additional attributes from both
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grids.
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To do that right click
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on the joined grid in the project table
of contents
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and select Joins and Relates -> Join.
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First join the BpS attributes
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by selecting the BpS field from the
combined grid,
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the original BpS grid,
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and its value field to base the join
on.
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Then click Okay. Now repeat the process
for the S-Class grid.
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select Joins and Relates --> Join.
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Then select the S-Class
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field, the original S-Class grid,
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and its Value field to base the join
on
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and click okay. Now,
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open the Attribute Table to check that the
Combine has been implemented.
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As you can see, both the BpS
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attributes and the S-Class attributes are now present
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in the Attribute Table. However, joins
are only temporary, so to make the join
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permanent you need to export it.
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To do this, right click on the combined
grid
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in the project table of contents and
select
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Data --> Export Data. In the export data
window,
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select Grid as your format then
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check the cell size and the export
location
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and click Save. When prompted
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to add the new grid to the project, click
Yes. Now when you open the Attribute
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Table
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you can see that both the BpS
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and the S-Class attributes have been
permanently joined.
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if you sort on the BpS model
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you will be able to see each BpS
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with its associated s-classes
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if you scroll across in the table.
Notice that
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there are now some duplicate fields in your
table such as multiple object ID and
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value fields,
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as well as the red, green, and blue color
fields from both
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input grids. You may want to delete the
unnecessary fields
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by going into the Data Management tools in
the Toolbox
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and selecting Fields --> Delete Field. That
concludes this demonstration
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of how to combine grids in ArcMap.
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