Apply your GIS knowledge in this course on geospatial analysis, focusing on analysis tools, 3D data, working with rasters, projections, and environment variables. Through all four weeks of this course, we'll work through a project together - something unique to this course - from project conception, through data retrieval, initial data management and processing, and finally to our analysis products. In this class you will learn the fundamentals of geospatial and environmental analysis during four week-long modules: Week 1: Tour ArcToolbox and learn how to use common geospatial analysis tools built into ArcGIS Week 2: Gain a working understanding of raster data models: symbolize, reproject, overlay, and assess rasters. Take a detour into 3D data models, and interpolation of observations into 3D surfaces and rasters Week 3: Go in-depth on projections and coordinate systems, which are foundational to all GIS. Learn how to use environment variables to constrain your analyses and get better quality data products. Week 4: Expand your knowledge of symbology. Learn how to visually display your data by classifying it in logical groupings and then symbolizing it on your map. Take Geospatial and Environmental Analysis as a standalone course or as part of the Geographic Information Systems (GIS) Specialization. You should have equivalent experience to completing the first and second courses in this specialization, "Fundamentals of GIS" and "GIS Data Formats, Design, and Quality", before taking this course. By completing this third class in the Specialization you will gain the skills needed to succeed in the full program.
Data Acquisition for Our Project
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来自 University of California, Davis 的课程
Geospatial and Environmental Analysis
498 个评分
University of California, Davis
498 个评分
课程 3（共 5 门，Specialization Geographic Information Systems (GIS)）
从本节课中
Course Overview & Geospatial Analysis
In the first module of Geospatial and Environmental Analysis, we will be learning about a plethora of common tools used with vector data in ArcGIS for geospatial analysis projects. By the end of the module, you will be able to use: the clip tool, erase tool, identity tool, near tool, point distance tool, merge tool, dissolve tool, tabulate area tool, buffers, and conversion tools. In addition, you will also begin work on a geospatial analysis project that we will be using throughout this course.
与讲师见面
Nick SantosGeospatial Applications Researcher
Center for Watershed Sciences
[MUSIC]
Hello, everyone, and welcome back.
In this lesson, I'm going to kick off our project in earnest and we're going to
start looking for the data that we think we might need for this project.
That's initially pretty vague because what data we need is up to us so
how we define our project defines what kind of data we need to go look for.
Now remember that the project is about what kind of agriculture is grown in flood
plains in California.
So intuitively, I think I'm going to need data on where the flood plains are in
California, and then on what agriculture is going on in California.
I doubt somebody's already compiled a layer for
me of flood plains in agriculture, so I am going to go look for
both of those pieces and put together the analysis myself.
Now I have an advantage here that you don't have, necessarily.
I know about water data already so I know which data sets I am looking for
usually or sometimes I know which data sets exist or
might exist so I can go looking for those.
In your own specific area of expertise, you have that advantage, too, or
you'll gain it as you continue working in GIS.
But sometimes we don't know what data there is and sometimes even when we know
what data there is, we don't know very well how to find it.
And I think we'll probably encounter that in this demo.
So I know that there is a flood plain layer for the United States.
And then I think that there's probably an agricultural layer that's publicly
available for California.
Not positive, but we'll go searching for both of these.
So for flood data, let's just look up flood plain,
spatial data, United States and see what we get.
A lot of this is about the art of the Google search.
And scanning through a couple of these, I see a few things.
One is floodplain for Montgomery County, Virginia.
That's nice.
That's not particularly useful to me, but, too, is the national flood hazard layer?
Now I happen to know that's the data set I'm looking for, but
I didn't pre-compose this query.
That was just my first Google search that I thought of for this.
So let's go take a look at the national flood hazard layer from FEMA,
the Federal Emergency Management Agency.
Now, whenever I get to a page that has some data on it potentially,
I go looking for big download buttons.
And I don't see one here, but
I can read about the data layer here to make sure it meets my needs.
And then, down here there's a section on accessing the National Flood Hazard Layer.
So I'll click down here.
It says I can download it using the FEMA GeoPortal or by downloading a KMZ file for
Google Earth.
And then they offer some web services which I haven't taught you how to use yet.
And then it can be downloaded from the FEMA Flood Map Service Center.
So, there are a bunch of options here.
Sometimes when there are a bunch of options,
that means that none of them are particularly easy, and
sometimes it's great because they provide a lot of things.
My initial intuition is that I should check out the FEMA GeoPortal though, so
let's do that.
And it warns me that I'm leaving the FEMA site, so'll I click OK.
And I opened it in a new tab so we can come back here,
because in case this isn't the page I want, I want this page open.
because this page is telling me what data is available.
So I center-clicked it, you can control-click or
right-click to open it in a new tab if you want to.
And all of a sudden I'm lost.
I get here and I'm not particularly sure where to go.
It looks like I'm on a general FEMA homepage here.
So let's look around a bit.
I want something on flooding.
I'm going to center-click that as well to open that in a new tab, but
at the same time, there's a gallery and a map section here.
So let's go take a look at the gallery.
And while that's loading I'm going to take a look at the flooding section.
So the top of the flooding section has FEMA's National Flood Hazard,
they're official.
I'm going to click on that and
see what it gives me And it looks like it's loading a web map.
This isn't particularly what I want because I want to download the data.
So If I zoom in over here,
it looks like the legend says National Flood Hazard Layers available for an area.
So it looks like it's available for most of California, and
especially California's Central Valley where a lot of agriculture takes place.
The initial thing is one, I haven't ruled out the ability to do my analysis yet.
It looks like there is flood plain data available for my area of interest.
I still don't know if there's crop data available, but
there is flood plain data available, so that's useful to me.
Even though I haven't gotten my data yet, I know more about whether or
not I can actually do my analysis.
Now I'm not seeing exactly what's going on here.
Maybe if I zoom in more, maybe there's some scale dependent rendering
where I'll actually see the flood hazard layer if I keep zooming in.
But there's a river in here, so yeah, so
it looks like all of a sudden, I should start seeing some different
data on my map when I'm zoomed in based upon the way the legend is.
So it tells me which panels of the FIRMs, the flood insurance rate maps
are available, and I can click on it and then I can go to download county GIS data.
So I'll center-click that to open that up just in case it's not what I want.
And it looks like it's downloading the package for this county.
Now downloading a whole county is great but
I don't necessarily want to assemble all the county data.
So I know that I can get back here and I'll leave this tab open,
but I'm going to go looking for an area that's larger so
that I don't have to do a bunch of assembly of different pieces.
So let's go back to our Google search here.
And I'm going to go back, and
I'm going to just open that page in a separate tab again so I have it backed up.
And then I'm going to do a different search,
just to see if I can find a national copy.
So, now that we know that it's the National Flood Hazard Layer,
we can search NFHL to narrow our search, and then let's do, just download.
And let's see what we get.
So the same page I was at, and then a GIS web services page here,
and then something on data.gov.
It looks like there are some other options here,
someone else having the same question, where to download FEMA DFIRM data.
So a number of different options here.
And I opened this one in a new tab, I thought.
Yes, I did, it's right here.
And there's a bunch more information here on how I can download the data.
Now it's telling me that there are some web services I can use.
And I know that there's a tool in ArcGIS that lets me take a web service and
copy it to a local file that I can use for analysis.
So that's good to know about, too.
And I can come back to that if I want to get a national copy as well.
But for now I'm going to skip past that.
To jump to the point, and spare you all watching me find this data again,
I did ultimately find a national copy of the FEMA data,
that I could then clip to California if I wanted to.
And I tried to search femenfhldata.zip, and see what I get,
and I did a number of other searches and I found out about a site called
femadata.com.
Or, oops, it was data.femadata.com and
then in the Federal Insurance and Mitigation Division section down here,
there's a risk map folder with the NFHL data in it.
And then from here, I can download the zip file in parts and then extract it.
Now, I didn't show you how I ultimately got here.
Still, just know that if you keep searching around,
you will find different ways to access the data.
So we found three different ways.
We found the county specific downloads,
we found the web services that I could use in arcGIS, and
then ultimately I found the data download here that I could use in my project.
And this is the one I'm going to use which is why I showed it to you here.
But if I hadn't found this while I wasn't recording,
you would still have these other two options for working with the data.
So there are many different ways of approaching finding data, and it's not
necessarily something where you know you'll spend x amount of time and find it.
You just need to follow the bread crumbs and seek it out and
see what matches with the skills you have or think you could have.
Maybe you'd be able to teach yourself how to use these REST services if you started
reading up on it and looking at the guides and things like that online.
Okay, so to continue, I'll download this GEO database here and
then I will extract it so THAT we can use it in the analysis.
And then rather than make you watch as I go find the California Agriculture
layer I will Find it myself and then download it.
And then I'll talk to you about the implications of what I've downloaded
once I have all the parts and we start to put them together into an analysis.
You don't need to go through this process with me more than once.
Really, the main takeaways from this are it takes time to find data.
You'll find many different access points with different properties and
capabilities that you can use.
And if it doesn't seem like one is exactly what you want, keep looking for
a little while, but keep those others in the background so
that you can find them still and use them based upon
what you think you might want later and as you find out more information.
Okay, that's it for now.
I will see you in the next video.
