So in this demonstration we're going to focus on Digital Terrain Models.
In particular we're going to look at how to build both a tin—so
a vector based triangular regular network data set.
And also, a raster based DEM or Digital Elevation Model data set.
So we're going to work with both of these throughout this demo and then
lots, and lots of different data layers.
So if you see here we have several different things we're gonna to work with.
We have some points we're gonna work with when we do some interpolation later on.
We have contour lines.
We have another type of points,
things that are called spot elevations.
We have water.
We have the outlines of some of the different parks
that you may be working with.
We're just gonna focus on Notre Dame again.
And then we have our already pre-built raster based SRTM or
satellite source of data.
And we're gonna work with all of these throughout this demonstration.
So because there are lots of different data types there's gonna be lots
of different little sections.
So if there's only one particular thing that you're interested in then I encourage
you to go ahead and look at the demo notes and try to find that section.
So go ahead and start off with a new blank map if you haven't already.
And the very, very first thing we do before we wanna add any data in is
we need to enable two extensions.
The Spatial Analyst and the 3D Analyst.
Now these are parts of ArcGIS that cost a little bit extra but
are part of the Notre Dame site license.
So for some reason you're at another institution that doesn't have a license
for these, then you won't be able to do a lot of these more complicated 3D and
Terrain Modeling techniques.
Fortunately, it's pretty common, so I would be surprised if you have a license and
don't have these particular extensions.
So to enable these, we're just gonna go to Customize, Extensions.
And then you simply want to turn on 3D Analyst.
See mine was already on, and Spatial Analyst.
Now if you work off the same computer, then these will stay in place.
If you work off different computers, or if you're logged in in the computer lab or
something then you may have to do this every time.
Fortunately, this software will let you know pretty quickly if that's the reason
why your tools aren't running.
So once we have these turned on, what
we would often do in a GIS class is you would go through a scanned TOPO map and
digitize, just like you did for the soils in the Creating Vectors lab.
The individual TOPO lines and the spot elevations on that TOPO map.
I'm not gonna have you do that because I think you've
probably already gotten the techniques down just by doing the soil maps.
So instead what we're going to work with is some pre-digitized topographic lines.
So go to add in your data.
Now again, if you need to know how to map to your data, if they're
not showing up with a link to that folder, then look at one of the previous demos.
And in Demo 10 data, you should have Michiana Contour Lines,
Michiana Spot Elevations, and Michiana Water.
So go ahead and select all three of those.
And add them in.
What you see is you have a pretty large area of TOPO lines, of spot elevation,
so high and low points.
And then the limits of water, as well.
And we put this in here, because when we're creating a surface,
we want water to remain flat.
We want, if it's a body of water like the lake in Potato Creek State Park down
here or the river itself, we want that to be flat.
We don't want that to be interpolated in any way,
we don't want the surface to sort of angle in there because that wouldn't
accurately represent what we would expect to see for a body of water.
Now the first thing we wanna do is use these data layers to create
a triangulated irregular network, so a TIN data model.
And this is fairly easy to do in ArcGIS,
especially when we have all of these different layers.
So what we want it to do is create surfaces between the TOPO lines and
the high and low elevations, but leave the water flat.
Now this is gonna be fairly, the settings on it are where it's a little bit more
tricky, and you're gonna wanna watch out for how you're doing this.
So go ahead and start up your Arc toolbox if you don't already have it up.
Once that comes up, we're gonna go into 3D Analyst Tools,
Data Management, TIN, and Create TIN.
And this'll open up the Create TIN window for us.
So first thing it's gonna do is ask us what we wanna output it as.
This is just sending it into a temporary location, I don't want it there.
I actually want to send it over into my Demo 10.
And this is one where you're giving it the entire name, as well.
And I'm going to call it TIN
Michiana.
Now if you're not familiar, I'm gonna use this word a few times, it's already been
in here, but Michiana is just the area of Northern Indiana and Southern Michigan.
It's sort of a clever way of saying the section where Notre Dame and
South Bend are.
It's gonna ask you what the coordinate system you want to use is.
You don't have to specify this here, but I would encourage you to do so.
We're gonna go down to use the same one we've used before, Projected,
UTM WGS 1984,
Northern Hemisphere, and Zone 16 North.
Now if you want, you could just right-click on this and
choose Add to Favorites.
And if you're using the same computer,
this will come up in your Favorites section from then on out.
Now we wanna use all three of these data layers, so
we're gonna bring all of them over.
Since they're already all selected in my Table of Contents, I can just drag them
over like this, or I could have chosen them individually in here.
Or found something that's not even up in my Map Document
by adding it from over here.
So it sort of guessed at what different the settings it wants to use are.
So, essentially the way that this works is we have sort of what
the feature type is, what the height field in there is, and then if there's any
sort of tags that we want to have on there. We're not gonna worry about tags here.
So, if we choose hard and
soft, in this case, it refers to the strength of the edge, particularly,
whether triangles can cross that edge, or whether they're very, very limited add it.
Replace would create, give an area kind of a systematic value.
Erase will leave it blank.
Clip would leave the limits of it, of the entire TIN restricted to that.
So let's go ahead and set it for each one of these.
So for spot elevations, this is true, the height field is elevation, ELEV.
If you wanna verify that you could look at it in the Attribute Table for that layer,
and you see that is, those look like elevations.
Because these are points we want them to be what's called Mass Point.
It should be the only option we have for points.
And so, that's all ready to go.
For the contour lines, Contour is the correct one.
Again, you could check it in your Attribute Table if you wanted to.
And, sure enough, Contour is the elevation above sea level.
The choice here we have is whether we want to do Hard Line or Soft Line.
Now hard line, like I said, is gonna give it a very layer-caked way of looking at it.
Because those,
no triangle will be able to cross the line between two points along that line.
So let's go ahead and switch it over to Soft Line.
That's gonna give us a better indication of what it should look like.
Now from Michiana water, what we actually want to do, even
though there are Z elevations associated with each one of those features,
what we actually want to do is turn this to be None.
So these are all of the bodies of water in there.
We want them to be flat within the model the way that it's been interpreted around it,
but not to try to guess if it's higher or lower,
not to try to use the values that are already in there.
Now we definitely don't want Soft cClip.
Because Soft Clip would go ahead and
cut out everything that surround those regions.
What we're actually looking for here is going to be Soft Replace.
Now why Soft Replace?
Well that just means it's possible to have those lines cross over a little bit.
So this is the way we wanna set in here.
Leave all the tag fields as None.
Go ahead and leave this Constrained Delaunay as blank.
If you ever want more information about what any of these tools are you could
always hit this Show Help button right here.
And then if I turn this on, it's gonna tell
me a little bit more about what that conforming triangulation algorithm is.
So go ahead and hit OK.
So it'll run for a few minutes in the background.
It's gotta do a lot of math.
It's gotta calculate the angle of all of those triangles.
The elevation of all the points and really begin to build it into a system
that will show us this elevation in a pretty effective model.
And there we go.
Our TIN has arrived, so
if we turn off all the other layers we begin to see what's happening here.
So you can see it rendering as it goes.
So if you sort of zoom in on it, you can see it's showing you
a sort of shaded elevation view.
So we have the river coming down here.
It's all been sort of left as flat.
And then we have the banks coming up around it,
up onto the hills on either side.
So at this point, what we could do is go ahead and convert this into a raster.
If we wanted to have this in a system that was a little bit more simplistic for
us to do some of these math calculations on.
And if we need to do that, that is also in here.
If you go into the 3D Analyst Tools and go to Conversion.
Gonna go from TIN to Raster.
Then you would simply bring over your TIN.
And I would go ahead and call the output raster
something like Michiana Converted DEM
.tif
The .tif is important here because otherwise it's gonna try to give it to you in
a different file format that couldn't have that long of a name.
And it'll give you an error.
So the first thing you should check if you get an error is whether you have that .tif
at the end.
So go ahead and hit OK.
So now we have a different type of DEM we could work with.
So we've done most of the interpolation in the creation of the TIN, but
then it's given us an actual DEM.
In this case, the range on it, just like it was with the TIN, is very, very low.
So it's not gonna be the prettiest DEM just because there's only
a few values really in there.
Northern Indiana, the Michiana region is pretty flat in general.
If you see one of these for, say, the Grand Canyon, or
Crater Lake like we saw in the lecture.
It does look a little bit more striking.
So let's go ahead and look at how we might do this in a different way.
So we found one way to create an interpolated surface by creating a TIN,
and then creating a DEM from that.
But we could also just go with straight interpolation as well.
So go ahead and turn off all the layers that are in there.
You can even minimize them down if you'd like to.
And we're just gonna add in interpolation GPS points here.
So what these are these are simulated GPS points taken across the entire
the same region.
You can see they sort of look roughly like the spot elevations
but they're not exactly the same.
And what we want to do is create an interpolated surface out of these.
So we're gonna do this, we have a lot of different algorithms.
I went over these in the lecture a little bit and I encourage
you to spend a little time looking at different algorithms if you want to.
But what we want to do is we're just gonna use the spline algorithm,
which is one of the more simplistic as far as settings go, ones that we could do.
Go into your Arc Toolbox,
go down to Spatial Analyst Tools, go to Interpolation.
And then we have Inverse Distance Waiting,
Creaking, Natural Neighbor, lots of different techniques in here.
We're going to choose Spline.
So you're gonna bring it over your point features.
It's gonna immediately ask you what the z value is.
It's elevation Elev here.
I'm gonna give it a permanent output name.
I'm gonna call this Michiana
Interpolated DEM .tif The only other
thing that I really wanna set in here is
I'm gonna turn down my output cell size.
It's guessed at what it thinks I should do based on the extent of the file, but
I want it to be a little bit more precise than that.
So I'm gonna go ahead and turn it down to 30.
And this'll just give it a better surface. So that'll run for a moment or two.
As it's kind of guessing at the points in between all the area in between
the points.
And it's gonna build it up for us in a way that has a nice view of the same area.
So I'm gonna turn off the interpolation points.
We don't really need those anymore.
And what it's done is it's given us something a little bit silly here.
So it's given us some really low values that's normal sometimes with Spline if
there is no data then it will give you very low, or very high values.
But it's given it to us in this sort of classified way,
which doesn't really show the data that I would prefer to for a DEM.
So I'm gonna go ahead and go into the Layer Properties for that DEM either by
double-clicking on it or right-clicking on it and choosing Properties.
And I'm gonna go over to the Symbology tab.
And we're just going to choose,
instead of Classified here we're going to move it over to Stretch.
And then I'm gonna go and switch it to one of those traditional
color ramps that we associate with topographic data.
It’s this one right here and that one right there.
So if those don't make sense, if you can't immediately see them and
have them look totally normally,
anytime you see this color ramp in ArcGIS, you can right-click on it,
turn off Graphic View.
And you'll see that those two are just called Elevation 1 and Elevation #2.
Makes it very easy to find the same color ramp again.
So go ahead and hit OK. Now this looks more like
an interpolated surface.
You can see that there's some little ball or sort of high and low points.
It's a rubberized surface, a spline method so
it's going to look sort of like this.
Now we can compare that to the DEM that we generated from the converted TIN.
And it's probably a good idea to go ahead and put that into elevation
the same color amp just for ease of sort of looking at these.
So you see, one definitely looks a little bit more pixellated but
it looks a little bit more like what we would expect to have as the true surface.
And one has some artifacts of that interpolation in there.
This is relatively normal.
So let's look at one other type of topographic data before we start thinking
about some of the different ways to do topographic analysis on these layers.
So we're gonna just add in this other layer, which is SRTM_Michiana_UTM.
So what this is saying is that this is the Shuttle Radio Topography
Mission from the latter part of the 20th century, I think 1999.
And then, it's from Michiana and it's using a UTM projection.
So this is just the name that I gave it to sort of make sense,
to have a lot of the data that we needed right there.
So just add that in.
What you'll notice first is it's a little bit bigger.
The values are roughly analogous to what we have for the other.
They go from about 200 to 275 in one, 150 to 300 in the other.
And these are probably a little bit more accurate, and
they go from 180 to almost 300.
So let's just change our color again as well.
Now we can begin to look at all three of these
and see which ones we think are giving us the best information.
So if there are any deviations across them, it may be a case that you have
missing data.
Those GPS points, they may have not been a very, very consistent,
like finding all of the spots that there really are important topographic changes.
It could be that you could edit the original file, build new ones,
you can create a better TIN out some of the other points.
And sometimes you would even need to make points or
poly lines to kind of trick the computer into creating the right surface for you.
And that's a technique that you can do,
you just need to be clear that you've done it in any further analysis.
So at this point we no longer need most of these sort of simple surfaces here.
So we don't need any of the factory data here.
We don't need the Interpolation Points.
We don't need the Contours.
Just right-clicking and choosing Remove.
And in fact we're just gonna go ahead and stick to our Converted DEM and our TIN.
So for the rest of this demo we're not gonna need the SRTM data.
We'll return to it in the next demonstration, or
a further demonstration on hydrology.
And we're not gonna work with the Interpolated Surface any longer.
So what I wanna show you at this point, is how to do some of
the different topographic analysis on both DEMs and TINs.
Cause the systems is different for each one.
So the standard ones that we've talked about before are things like the Slope,
things like the Aspect, things like Hill Shade, Contour Lines,
any of these different things.
And we're gonna start off doing this on the DEM.
Now the big difference between doing it on a DEM and doing it on a TIN is a TIN,
you can do it on the fly.
You can just change how it's displayed to show you any one of these different
characteristics.
For a DEM, you're gonna create an entirely new raster layer that is that
calculated surface, and that's an intentional choice.
That way we can use those layers in different types of analysis later on.
So to start off we're just gonna do a Slope Raster,
that's gonna be our first one here.
And most of the things we're gonna work with are gonna be in
the Spatial Analyst Tools in ARc toolbox, and down in Surface.
So let's go ahead and run Slope.
And we simply bring over our DEM as our input raster.
Our output raster, I'm gonna call it Michiana_Slope,
.tif
It'll let you set the output measurements if you wanted to have any sort of z
factor, if you wanted to convert at this point between meters and feet or
something like that.
So we're gonna go ahead and hit OK.
It'll take just a second to run.
And now it’s given us a measurement where the slopes range from 0 to 7.6,
or so, of the areas of higher slope in red and lower slope in green.
Now obviously if you're doing this for a different area,
the values in there are gonna change.
But this is sort of the standard color ramp for slope,
this sort of green through yellow to red.
So the next one we wanna do is to look at the aspect, or
the prevailing direction of every pixel, and it's exactly the same.
We're just simply gonna bring over our DEM as the input raster.
We're gonna call the output raster, Michiana_Aspect.tif
And once that runs, it's gonna give us a slightly different measurement. Where we
have anything that's flat is gonna be a -1 as the value, it's in sort of grey.
And anything that's north, whether that north is 0 to
22.5 degrees or 337.5 to 360 degrees is in red.
And all of the other kind of sections of the compass are colored in different ways.
Now it is presented as categorical here, but
underlying it we have the actual angular values.
So for any individual pixel, if we wanted to use the Identify tool, and
click on an individual pixel in there, it's actually giving us that angle,
104, in that case.
So something that's gonna fall into this generally kind of east category.
Now we'll get to, in a later demonstration,
the concept of reclassifying.
And these data are frequently reclassified,
so that whatever your prevailing direction that you want is,
gets a higher value than the directions you don't want.
Now another one we can do is called Hillshade.
Again, we're just gonna bring in our DEM.
Gonna call it Michigan_Hillshade.tif
And then it'll allow us to set our azimuth and our altitude, so
the angle that the sun is coming from and the angle above the horizon.
We could do some of these other options if we wanted to, but
I'm just gonna leave them as is.
And what this'll end up giving us is a layer that, for
that particular orientation of the sun, is showing us the areas that
are more shadowed versus the areas that are more well-lit.
This could be very useful for things like putting solar panels or understanding
different vegetation regimes, that are sort of based on climatic characteristics.
Now I'm just turning some of these off, minimizing them.
Now the last one we're gonna do,
is one that doesn't actually give us an output of a raster.
It'll actually give us a vector output, and that's this Contour one here.
And what this will let us do, is create a new contour line layer.
Using whatever DEM we have, we can now create
we're just gonna call it Michiana_Rebuilt_Contours.
And it's gonna give us a shape file.
So if I wanted to give it say, every 2 meters,
it'll give me a contour of every 2 meters.
Now in this case this isn't exceptionally useful because I've already
built it off of a contour layer.
I have one already, but say I downloaded A raster DEM from some place,
and I wanted to create a contour map, something that someone else might be able
to see a little bit more clearly what's going on.
This would be how you would generate a contour map from something.
So you can see that even though it's a little bit pixelated so
some of the lines are a little more straight than what you might normally see.
It has created a nice contour map for us out of this layer.
So those are the main ones that we want to do on the DEM.
Now I wanna show you how to do some of these on the TIN layer,
cause it's a little bit different.
So I'm gonna turn off everything but the TIN.
It's just taking a second to render, zoom out a little bit.
Zoom in a little bit more.
Now, when I want to set different things to see some of these different
characteristics, all I have to do is go in to my TIN, the Properties for
my tin layer, go over the Symbology.
And then it's actually giving me a list of different things I can see over here.
So right now I'm seeing the edge types and elevation.
I don't really need to see the edge types.
I can remove those and now it's not showing me those contour lines any more.
But I can also add a bunch of other things in.
So if I wanted to, say, add here, I can do my Face Aspect with graduated color ramp.
So I'm gonna add that. My Face Slope with a graduated color ramp.
If I wanted to do Contour Lines and
Elevations, I could have all of these in here as well.
So I have a lot of different things that I can show on my renderer here.
So once I'm done with adding, I'm just gonna hit Dismiss.
And now all I have to do is turn off Slope.
Turn off Elevation, all these other things.
And now what I'll see in the background is the Aspect.
If I do the same thing for
Slope, whichever one is on top and turned on is going to be what I see.
And I can always reorder them if I wanted to here.
So I can show my Hill Shade effect down here even in 2D effects or
even in 2D sections.
And if I want to, I can always go back to elevation.
So I'm just sort of showing my elevation here.
I could change how, what the colors were.
I can change pretty much anything I wanted in the Symbology tab by
choosing what layer.
And then choosing things in this Symbology.
So it's a lot easier to show these things interactively with the TIN.
I don't have to create a new layer.
But what that also means is that new layer isn't available for
me to use in any further analysis later on.
So just to, sort of, finish up, I wanna show you a few of the things that you can
do that are a little bit more, even more interactive than working with TINs, and
we're going to do that by turning on the 3D Analyst toolbar, which
gives us some things that we can do just sort of on the fly.
So again to turn on a tool bar you're just going to find a gray spot at the top of
the screen, right-click turn on 3D Analyst.
I'm just gonna drag mine up here and dock it.
Now, like a lot of these,
whatever layer I have this pointed at is gonna be the one that I'm working off of.
And then I have a lot of other tools.
So I have a drop-down with a bunch of options I could set if I wanted to.
I'm not gonna change anything at the moment.
And then I have a lot of other sort of interactive things I can do over here.
The first one, what it's gonna do is it's gonna create a single contour that
shows me everything that's at that same elevation, so
if I click, sometimes it's hard to hit a good spot.
If click right there it's now showing me everything that's
at that exact same elevation.
The second one here is going to create what's called a steepest path.
So if I hit some place up high, it's gonna show me, eventually, again
these are very hard to hit on something like a TIN.
It's gonna show me the steepest path down from wherever that point is.
Obviously I'm not hitting any very well in here.
So I wouldn't really worry about those too much.
The next one here will show you what's called a line of sight.
This is a type of view shed analysis where I can now set my Observer.
So say in this case these are meters so.
We'll say 2 meters, it's a very tall person.
Looking at something that's, say 5 meters tall, looking at a building.
So now if I click my Observer and then my Target, I can see whether or
not they can see that thing, what's blocking it, and
anything that's visible in between the observer and the target.
So you can create these sort of across the entire thing.
Finding one that you can see a big area is usually relatively difficult.
Though that's a pretty decent one right there.
I can also do things like create an interpolated point.
Line or polygon across the surface, so it's actually gonna give me something
that's a graphic, although not a true shape file or vector data.
That's going to give me the ability to kinda copy that between different Arc map
documents, and not do a lot of analysis, but have that same thing visible.
It can be useful when you start working in three dimensions.
Eventually, you'll end up with a whole lot of things on here that are drawings.
If you are tired of them you can always go to Select Elements,
sort of drag around them,
and then just hit Delete. You might have to find ones that you missed and
just get those as well.
But if you just choose them with this black arrow tool and
then delete them by pressing the Delete key, it works pretty well.
So the last thing I'm just gonna show you one interpolating a line here.
Because this is the one that's actually pretty neat.
So if I go through here and I choose Interpolate line,
what it's gonna do is it's going to place
that line graphic that I just created across the entire surface as well.
Doesn't look like it at the moment, but
what I can also then do is go to this Profile Graph button right here.
Once I have something like that interpolated line selected,
I can choose Profile Graph, and it'll generate for
me a graph of the topography of that line.
Now that could have been a complicated line,
it didn't have to be a straight line.
It's a good way to give yourself a good profile graph of a particular area.
If you need to change any of the specifics on here
it's basically up if you right- click on the title some place and
go to Properties, you can change all of the different titles and subtitles and units.
Now the last part of this that's pretty neat to do,
I'm just deleting that last one.
Is if I create a line of sight.
I can do that same thing.
I can create a profile graph from my line of sight, that'll show me,
just dragging it out a little bit bigger, maybe why I can't see anything.
So I was behind a hill, is why I can't see anything on the other side.
So it's a good way to be able to create an interesting visualization
of the three-dimensional surface.
So we work with these and some of the other three-dimensional tools in a later demo.
Particularly, we also have the ability to go into the three-dimensional versions
of ArcGIS, ArcScene, and ArcGlobe.
We'll work with these in a later module.
So that's essentially it for
working with topographic data, DEMs and TINs.
In the following demonstration we're gonna apply some of these skills when we start
working with spatial modeling, both hycological modeling and
sort of more generic modeling.
I do encourage you to take a look at whatever assignment there is for you for
this week, for this module.
And feel free to contact us with any questions.
Thank you.