Hi everybody and welcome to the to the second of these GIS modules hosted here
through the Center for Digital Scholarship at the University of Notre Dame.
In this module, we're going to be focusing on raster data.
So, just like they're all gonna start here,
I'm just showing you where the file should have been saved.
These are the things you should be looking at and
what we're gonna be dealing with for the demonstration here today.
So if you look in this Demo 02 folder here,
you have basically two files each, one of which is a raster data layer,
these are two different satellite images, one from 1973 and one from 1987 that we're
going to be manipulating and working with in this particular demonstration.
So, if you haven't already, go ahead and start up ARC JIS or
ARC MAP through the start menu, and go ahead and,
if you're still seeing this menu, just choose blank map and hit OK.
So, in the last module, in the very first one, I just went over a few of
the navigation things, and saving files and stuff like that.
So please refer to that if you need to, but just as a little bit of a reminder,
when we add data we're gonna use this particular tool
to bring in our new data layers.
And if yours hasn't already shown up someplace like this in one of the demo
folders, you're gonna choose this connective folder to map the location,
to map essentially a bookmark to the folder that you're storing all of your data in.
See we just go in and choose wherever your GIS folder is.
Choose the root folder and hit OK, and then go in to demo 02 data
and either by just holding select or
dragging around both of them, we're gonna add in both these layers here.
So go ahead and hit OK or add, and what you see is we have two different layers,
one of which, like we learned about in the lecture,
is grayscale, so it's a panchromatic image, it's black and
white, and the other is color, and you can see that one,
the color in particular is significantly lower resolution, spacial resolution.
We see a lot less data in there, and that's even more true if
we begin to zoom in on it, so we zoom in on Notre Dame campus here.
We can see decent detail in our panchromatic higher resolution one here,
and much, much lower resolution, we can see the individual pixels in
the panchromatic, I'm sorry, in the multispectral landsat image there.
Now, that's not always the case.
I don't want you guys to come away from this thinking that
multispectral imagery is always lower resolution than panchromatic imagery.
Although it often is, it doesn’t necessarily have to be.
So we’re gonna start off just by dealing primarily with the grayscale image
because it’s easier to run any of those filters to do any of those sorts of analysis
on a single band then image than it would be to do it on a multi band image, and
then we'll do a little bit of the multi band stuff at the end.
Let's just go ahead and turn off that Landsat image for now.
And the very first thing we wanna do is begin to manipulate
how we're going to view this particular image.
And we get to a lot of this stuff in what's called the layer properties.
So in this particular spot image, we can either right click on it over here in
the table of contents, or just double click on it very quickly, and
if you right click on it you're gonna go down to the properties here.
And what we'll end up with is a whole series of tabs that
are essentially information about that particular layer.
So general would let us add at things like change the layer name,
how it's displayed over here, if we wanted to give a description or any credits.
If we wanted to control how it's shown, if it's only shown if we're zoomed in
a certain level or if we're zoomed out a certain level.
The source is gonna give you all sorts of information about it,
the number of columns and rows, how many bands, the spatial resolution,
so essentially the cell size of each pixel, what
type of pixel it is, this is a case that's an 8 bit.
Some things about the location of the image itself, the coordinate system,
these are all things we'll get to later on in the semester.
We could also, the particular metadata one here we're
not gonna deal with this very much, but we could enter some additional stuff about
what wave lengths are being sampled, stuff like that.
The extent would allow us to sort of display when it's displayed and
how much of the images.
So if we had an image of the entirety of North America, but we were only looking at
Northern Indiana, we might want to set the extent very differently.
Display will let us do a few things, we can set the contrast and brightness,
we can make it transparent or not transparent.
We could do some different choices of how it's displaying the image in general,
whether it's displaying all every individual pixel or
whether it's doing a very quick rendering of it.
Let's just try to do a quick little change of the brightness and contrast right here.
So if were to crank the contrast up to 70 and the brightness to 30,
if we hit apply it's going to run it on the thing behind us, if we hit OK,
it's going to close this window, but if we wanted to make it sort of stick around we
could hit OK, but let's just hit Apply, because we're not going to keep this.
And you see that changes the image quite a bit, so let's just go ahead and
put these back to zero.
And hit Apply again, and our image is back to where we're used to seeing it.
Now the real, the one we're going to work with the most for
changing imagery and how it's displayed is this Symbology tab right here, so
just go ahead and click on Symbology.
And this is pretty common, we're gonna deal with this particular tab, both with
raster data this week, or this module, and then with vector data in the following module.
But basically what we were able to change here are just a few things,
we can change the high and low numbers that are going to be displayed,
I want you to be aware that this is not going to change the actual high and
low values, it's just going to change what's being displayed.
We can change what type of stretch is being applied to it.
Now, I think I said in the lecture that Arc GIS always brings in images with some
stretch on them, so you see right now, we have a percent clip stretch.
What this is basically doing is it's just cutting off the highest and
lowest 0.5% of the image, so let's try to turn this to none and hit Apply.
So this is what the image actually looks like.
There's a lot of very, very dark stuff in the middle, and
a few sot of really light white spots.
Now I would encourage you guys to go ahead and start play around with looking at what
different stretches do, standard deviations is pretty standard.
This is a pretty common way to view these images,
as is the minimum maximum is another one,
it's basically just stretching it between the lowest and the highest values.
The few of the others are a little bit different.
Percent Clip is again that default we've had before, but really the reason
we're doing these changing the stretches here in the Layer properties begin with is the ability
to actually get to the histogram itself, like what you see right here.
So, go ahead and click on that histogram button, and
this is where we can begin to do some custom histograms.
So, this is our normal histogram.
You can sort of see, there's lots and lots of grey stuff.
There's not a lot that's very very bright.
Most of the values are sort of less than 100.
There are a few peaks in there.
Now, if we wanted to do a custom one here, we could begin to drag that histogram in.
So, what it's going to do it's going to stretch.
What was previously this value here, all the way out.
That becomes a two fifty five.
If I do the same thing, drag it in a little bit here.
What was previously, let's say, like a 25 here is now being displayed as a zero.
So, you can see the new histogram behind the old histogram.
I'm sorry, the new histogram in purple and the old histogram in gray there.
So, if you hit okay and apply, you can see it doesn't change things tremendously.
That's kind of what a lot of the other their histograms are doing.
But, I want you guys to get an idea of how you change these histograms,
and how you begin to display them in an interesting way.
Once you've sort of played around and
created one of your own if you're in there and you're doing it you
might notice that you can pretty quickly do some other kind of weird things.
You can move this down.
Try to leave them at the top and bottom.
You can put in additional ones that put in, sort of,
other things that may not make tremendous amount of sense.
And sort of go backwards in there.
Those are really complicated ones that begin to look a little bit more funky.
So, if you get to one of those and it's just really, really not working for
you,at all just go ahead and switch it back to none and apply.
Go back into the histograms.
And you can always click on these things to sort of move them around, and
delete them as well.
So, just be careful with them.
Ad if you drag the little buttons that are off the edge, then they disappear, so
that's back to the original histogram.
So, once you're done, go ahead and leave it on standard deviations.
Hit apply, hit OK.
And I just wanna show you the other way to begin to deal with the histograms,
because this is where we're gonna be working with a few of the other
types of image analysis that we're gonna work with.
So, we have an additional kind of pane that we can get to.
In Windows up here we have what's called the Image Analysis window.
So, go ahead and choose that.
Yours probably wouldn't pop up exactly where mine did.
It probably popped up something like this.
All of the little windows like this can be docked.
So, if you sort of have it floating like this,
you could run the mouse over here and it's gonna dock it over in that corner.
This will kind of make it appear and disappear.
You can really put them wherever you want.
I'm particularly partial to having mine over here, and a little bit smaller than
they like to, but you're welcome to do whatever you want with it.
And you see we have sort of 3 main parts in here.
We have the layers that we're dealing with,
should look very very similar to your table of contents.
We have choices of how that layer’s displayed, and
then we have a bunch of different processing things we can run on it.
So, essentially what happens is once I choose a layer up here, in the top part,
I can begin to run any sort of processing or begin to change the display on it.
So what you see, here I can begin to play with the brightness and
contrast just like I was before, it’s just a little bit easier to get to now.
If you ever want to bring it back to the default you just choose these buttons.
It brings it back there.
I can begin to make it transparent.
This would be particularly important, if I had a layer underneath it.
But I can also begin to play with the stretches here.
I can't do the custom ones quite as well, but I can go through and actually just
look to see what the difference between these different stretches might look like.
So, again, just play around with those a little bit, begin to display them,
however, you might want to.
Now, the very bottom section here, like I said,
is where we do the real big analysis stuff.
We can do things like clip our image, so basically, like you would in Photoshop,
just cut it down, crop it.
We can save individual copies.
We can do a few other kind of things in here, and most of them will have a little
pop up that comes up if you sort of mouse over on them.
And then, you have the three other sections down here.
This very very first one here, is going to let us
apply any short of shaded relief if we had an elevation data set.
Which is something we'll get to later on in this semester.
The second one will allow us to do mosiacing, so if we have multiple
parts of an image, and we want to sort of fit them together we can do that there.
That's something we'll get to in a later module as well.
The third one here, is where we run those convolution filters that we were talking
about in the lecture for this week.
So, if you look in here, we have a series of drop downs.
Some of these should look familiar, sharpen and blur,
essentially high pass and low pass filters,
these various other ones we're going to pick out when there's A sharp difference.
So, this horizontal line detects, vertical line detects diagonals.
We have ones that look for less sharp things that look for smooth sections.
We have a couple of regular three by three kernel filters we have a couple of five by
five kernel filters in here as well.
Now, there are ways to get to custom ones and
ways to do more additional ones, but we're not gonna really deal with those in
this particular demonstration they're sort of hidden away in other parts of it.
But let's go ahead, and
run a regular sharpening three by three filter on this particular spot image.
Make sure your spot image is selected up here.
Just use sharpening three by three, and then,
as soon you click this filter button it's gonna run it.
So ,it's now increased the spatial frequency.
So, it's basically found places where it's a little bit different and
made it a lot different.
And you can sort of see what that looks like in here.
Now, I encourage you guys to run several of these things,
run as many as you want to.
Play around with looking to see what they might look like, and
what they're different.
At the moment, anything that you've run is temporary.
So, this Filter_SPOT is a temporary file that's not saved anywhere on your hard
drive, that you can get to easily.
Once you've run a few of these things, you probably want to save it permanently, so
to do that your going to click on it up in the table of or the image analysis
thing here and then this little save button over here this particular one does
save an individual layer so its gonna actually have you export it.
Now, this is a little pop up that you're gonna get familiar to, or
familiar with as you work through some of these different demos that I have here.
And it's kind of an annoying thing.
This is another sort of legacy file format.
Old computer thing, specific thing about ARC GIS.
And essentially what it is, what we're looking at is it separates out
the location of the file so the folder that it's being stored in from the name.
So, to save it is in a particular location you're gonna click on this little button
over here.
If it comes up in your demo to folder, well that seems like it would be great.
You could just hit add but that doesn't work.
You have to actually go find it the folder itself.
Click on it once, so it's highlighted and then hit Add.
And then it's gonna bring it up in there.
Now I'm gonna call this HiPass_SPOT_1987.
So I'm just gonna change that to HiPass at the front there.
Now that's just because you remember a sharpening filter is a high-pass filter.
Hit Save.
It's gonna run happily in the background and make a copy of it and
what that is, it's gonna ask me if I want to add it, I'm gonna go ahead and
say, yes, and now it's added it in as a permanent file.
This is a permanent file this one is not.
Now you see they look a little bit different, and
that's because when I add something into ARC GIS, it puts a stretch on it.
So it's already put a stretch on the image, and there wasn't one on it before.
So that's why they just look a little bit different.
Once you have that new permanent one in,
you can always just remove the old one, the temporary one.
If you right click on it, and just choose remove.
So go ahead, and experiment with other filtering techniques, other stretches.
What this is going to do is it's going to highlight particular types of
landcover for you.
And begin to sort of show some things that you might not be able to pick
out with your naked eye.
So once you're done, let's go ahead and
work on the multi-spectral image a little bit.
So we've been working just with this black and white, panchromatic,
all visible light, reflectivity, spot image.
But let's go ahead and switch over to looking at the landsat one.
You may want to zoom out a little bit if you haven't just because it is such
a dramatically lower spacial resolution.
If you've added it in and it asks you anything about building pyramids or
calculating statistics you do want to go ahead and say yes to all of those.
And when we've added it in what you very quickly see is that is has band
one in red gun, band two in the green gun, and band three in the blue gun.
That's just the default way that it adds it in.
Obviously, you probably immediately look at this and
say that's I'm fairly certain those aren't the colors of Notre Dame, Indiana.
And in fact that's true, that's because the wavelengths of light that are being
displayed in those particular guns are not accurate to
the true life colors that we would see with our eyes.
So there's, if we go into the actual layer we
might want to turn off the stretch just to see what it would look like without it.
So go ahead and go in and just,
if you're in the Symbology tab, just go in, turn off, no stretch.
So that's what it generally looks like without, that's not
particularly a great view, also because these bands are not red, green, and blue.
So essentially what we have in the land set image like this,
an older land set image.
Is we have four different bands, two of which, 3 and 4 are from the near infrared.
2 is green, I'm sorry, 2 is red, and 1 is green.
So if we want to make this like something we're relatively used to seeing,
at least from satellite imagery, we actually want it to be three to one.
So what this is showing us is near infrared red and
then green in the different colors.
So if you hit OK, you'll see it changes to be one of those
red images that we're used to seeing as satellite images.
Let's go ahead and put a stretch back on here.
I'm just gonna do standard deviation.
So, what we begin to see is areas that are red are probably more heavily vegetated
areas that are sort of gray like this are probably either fallow crop fields or
construction, like built up areas, and in fact this is South Bend, Indiana.
This is part of Notre Dame campus, the really, really dark
areas are water because water absorbs almost all infrared light.
So we can see pretty clearly what we're looking at here.
If we want to play around a little bit with the bands as they're being displayed
we can go back in there.
We can always turn them off so that we're just seeing an individual band.
So if we just wanted to see what was happening in the blue gun
there we can do that.
And we're seeing what it looks like sort of scaled from no color to blue.
We can just leave one out.
I find those not the easiest way to visualize data.
In fact, if I'm more interested in one particular layer,
I think it's better to switch it over to stretched here.
What that does is it looks at one individual band at a time.
So if I just look at band 3,
sort of scaled from light to dark, I could do that.
If I just wanted to look at band 4, I could do that too.
Now, again we want to leave it on RGB composite because that's kind of
the classic way to look at color imagery like this, but if you needed to
sort of investigate a particular band you could do that in there.
So, the last thing that we want to do here is, I wanted to
show you just a little bit about how to work with multiple files, simultaneously.
So, what we have, this is pretty common we have multiple layers in here.
We have a dark, we have our panchromatic layer,
we have our multi-spectral layer and there are some tools in the image analysis for
sort of displaying these things at the same time.
Now I can kind of click them on and off in the table of contents or
over in the image analysis window.
That's all fine and good, but
sometimes I wanna see them in a little bit more detail than that.
So there are two tools in here that you can use to do this.
The first thing that you want to make sure you have is the top layer selected.
So whatever layer is on top, I would select it over here.
And then this one right here is what's called the swipe tool.
So if I click on that, you see that suddenly I
have this sort of arrow that moves around depending on where I am.
Now as soon as I click I can kind of drag
one layer back off of the other one like that so
you can sort of see a few comparing the layers just sort of by dragging.
And I can come from any one of the four main corners of it.
[NOISE] Now the other tool I have is again with top layer of selected,
I have this flicker tool.
So if I click on that, it's gonna just start flashing them.
Then I can start setting this to go higher or slower.
It's the number of I think milliseconds between flashes.
They start getting really low and it's almost kind of nausea inducing.
That's another good way to be able to see multiple layers at the same time.
Alright so that's pretty much it for what I wanted to go over today in this particular demo.
Again, as always, if you have any questions feel free to send me an email or
talk to anyone on those sort of forums as they might exist for
whatever incarnation you're taking these demos for.
Additionally, there is an assignment associated with this
particular demonstration with this particular module so go ahead and
take a look at that and turn it in in whatever way is as expressed to you.
Otherwise have a fantastic day, and I hope that this was helpful.