So in this fourth demonstration,
we're gonna work on georeferencing and projections.
In particular, we're gonna take some scanned images of different
pieces of maps or satellite imagery.
We're going to fit them together and make them conform to the geometry of the Earth.
So, if you look at the file that you should have downloaded,
the demo four file here,
you can see we really only have three things:
three different .jpeg files, or digital image files.
We have two that are quad sheets, or
pieces of one quad sheet for South Bend East.
And then we have one that's an aerial photograph from 1998 of Notre Dame Campus.
So these are going to be the ones we're working with.
If you were to load these up in Photoshop, or just double click on them in Windows,
you'll see that they are just regular images.
There's nothing inherently spatial about them yet.
But let's go ahead and add them in.
So we'll start a new document.
Our new blend-like map here and just like we had in weeks past,
we're gonna use the add data button to bring them in.
So we're gonna go into demo four.
And let's start off with just adding these two quad sheets in.
First we're gonna take these scanned images and
turn them into something that the GIS can work with.
And then afterwards we're gonna work with that aerial photograph there.
So go ahead and select both of those and hit Add.
It's gonna build some statistics and histograms in the background.
This is just a way that it renders it more quickly.
And then it's gonna come up with an unknown spatial reference error.
This is all right, we haven't told it where it is yet,
so we expect this.
But if you ever see this error with something that you think you
have already georeferenced, or should already be georeferenced,
then you might have a little bit of a problem.
So what you see if you turn them off and
on and/or move them around on the table of contents
is we have quad one and quad two, these are pieces of the same image.
And what you see actually is that we have a scanned map.
This is the bottom half. Two is the top half.
And in fact, there should be some degree of overlap between them.
And this is very frequently what happens when you scan maps is you
get one that doesn't scan perfectly like this.
And you want to actually digitally remove that sort of stuff.
I'll be working with that, but the first thing we need to do is we need to make
them fit to the real world somehow.
So we're gonna work with one first.
So let's just turn off two for the moment.
And if you notice, if you zoom in on the corners here,
you should see that we have coordinates written on this map.
But what we see down in the bottom here, is unknown units and
something really, really big.
The map is currently in latitude and longitude.
You can see the coordinates written on here.
And what we're seeing down here is clearly not latitude and longitude.
And in fact what this is, is that it's simply the number of pixels out
from the top left corner of the map.
So what we want to be able to do is tell the computer
first what coordinate system we are going to be putting this map into.
And then from there we want to go ahead and start finding tie points or
ground control points between this map and the real world coordinates.
So the very first thing we wanna do is figure out what
coordinate system we're working with.
And this is almost always written on the maps themselves.
In this case, this is the North American Datum of 1983.
But then there's also a North American Datum of 1927.
And in fact it's this one is the one we're going to be working with.
The ’83 is on there but it's sort of these dashed corner ticks.
What we want to work with is the one that is the actual corners of the map.
So I'm just telling you that this is the NAD 1927.
So, the first thing we want to do is tell this map document that that's
the coordinate system we're working with.
And we do that in the layers setup here.
So, instead of double-clicking on the layer itself, we're going to
double-click on Layers.
And, if you're not on the Coordinate System tab you want to navigate to
the Coordinate System tab.
And then we're going to simply work our way through these menus.
We're gonna go into Geographic Coordinate system.
So it says latitude and longitude.
It is not a projected coordinate system yet.
North America, and then just scroll down until you get to NAD 1927,
and these other ones, just ignore them.
It's the base one here that we want to work with.
So choose that and hit OK.
And now we're ready to go
because if you look down in the corner now, we're seeing decimal degrees.
That's not an accurate decimal degree number,
so it knows what the coordinate system is, but it doesn't know where they are.
In fact, numbers that big in a geographic coordinate system would be seven or
eight times around the entire earth.
So we want to be able to tell it where the points that we have in common are,
the known points.
And on this map, those are gonna be the corners here.
Now, the next thing we want to do is we want to turn on what's called the Geo-
referencing tool bar.
And mine is already up up here.
You probably don't see Georeferencing anywhere up on your toolbars up here.
And if you don't, you wanna just find a blank space up there sort of in gray.
Right-click and turn on Georeferencing.
So I just turned mine off, now I'm going to turn it back on.
Now the way the Georeferencing toolbar works,
is it's pointing at one particular layer.
This is really important as I can only do this for one layer at a time.
Now right now it's pointing towards East quad two.
That's not what I want.
I want it to be pointing towards East quad one.
So I'm gonna change that over to be Southbend East quad one.
Nothing changes, but it's now going to work off of the layer that I have visible.
So, what we want to do now is define ground control points and
tell ArcMap where those coordinates are
so that it can work the image to fit onto where it's supposed to.
And in fact the easiest ones for us to use are the corners of the map.
So we're gonna look at this one first.
And we're gonna use this tool right here,
these sort of green and red arrows or crosses here.
And this is gonna allow us to add a ground control point.
So we want to click on that.
And you see now I have a new little crosshair thing.
I'm gonna zoom in quite close onto that corner.
And I'm gonna run my crosshair right as close over it as I can.
Click once.
So once I've clicked once, you see I have a little green one that's shown up and
if I drag my arrow out, it stays there as well.
So this is what I would do if I was tying two images together.
And this is what we'll do later on is we're gonna find the same thing in one
image and move it to the other image.
In this case, our ground control points are actually just coordinates.
So what we want to do instead is right-click.
And we have the ability to enter an x and y coordinate, if it was projected,
or the degrees, minutes, seconds of latitude and longitude.
And we're gonna choose this one.
We're gonna choose degrees, minutes, seconds of latitude and longitude.
So we have that information written right here.
This right here, 41 degrees 37 minutes 30 seconds, is our North latitude.
This 86 degrees 15 minutes 0 seconds.
(so if there's no seconds, it's inferred to be zero),
that is our West longitude, so we're gonna go ahead and fill those in.
So in this case this would be 86, 15, 0.
Now this is important: we're in the Western Hemisphere in Indiana,
so we're gonna choose West.
And then we're going to go for 41 degrees,
37 minutes, 30 seconds, North latitude.
Now when I hit OK the map's gonna disappear.
That's normal,
because what it's done is it's moved the map to that particular spot.
Easiest way to find it at this point is to right-click
on it in the table of contents, choose Zoom To Layer.
So now we see we have a red one, cuz it's moved that location to right there,
but the coordinates still don't really make sense.
That one is fine there, but it's inferring that one pixel is one decimal degree.
So we're actually getting really, really huge numbers as we move across.
So we need to be able to set the next coordinate to give it kind
of the scale of the image.
So I'm just gonna zoom in on the other corner over here,
Gonna find my cross-point as best I can, click once,
then right-click Input DMS of Longitude and Latitude.
And this one is going to be 86 degrees,
7 minutes, 30 seconds West longitude,
so let's fill that in.
86, 7, 30. Again, we need to make sure it's West.
And our North South, our latitude coordinate,
it's guessed at what it thinks it is based on where I clicked.
It's a little bit wrong, but at least now it knows it's in the Northern Hemisphere.
So it's getting a little bit better every time.
In this case it's gonna be 41 degrees, 37 minutes,
30 seconds North latitude.
So again once I hit OK, it's gonna probably disappear on me.
But if I right-click on it in the table of contents and Zoom To Layer.
Now if you look in the bottom over here, you see that
the coordinates are starting to look like they make a lot more sense.
It's not perfect yet, we need one more coordinate to really get it right and
then one more after that to test it, but it is getting significantly closer.
So let's find another corner on here to put in the coordinate zone.
So I'm gonna zoom in on the top corner, and unfortunately this is where the map
cuts off, so I don't actually have a coordinate on the corner like that.
So I have to find a different one, and what you want to do is just simply scroll down
until you find something that looks like degrees, minutes, seconds.
These are some sort of state plane system, we are going to ignore those.
But right here I now see 40 minutes, but what does that mean?
If I keep going all the way down,
if you remember my latitude coordinate on this one,
Was 41 degrees, 37 minutes, 30 seconds North latitude.
That next coordinate up there is gonna probably be 41 degrees,
40 minutes, 0 seconds.
That's exactly what it is, it's just because it's the edge,
because this line is 86 degrees, 7 minutes,
30 seconds West longitude, it doesn't repeat that coordinate.
It just simply increments this up to whatever the next one would be.
So it's actually going to be 42 degrees,
40 minutes, 0 seconds, with the same longitude on there.
So I'm gonna go back up, find that 40 around the outside there,
gonna click once on the cross right there, right-click Input DMS.
So it's actually done a very good job on the longitude, that is correct,
it is 86 degrees, 7 minutes, it's 30, so
we're just gonna cut off the rest on the West longitude there.
And my latitude, if you remember, is 41 degrees, 40 minutes, 0 seconds.
So it's gonna not move it very much this time,
in fact, it's just gonna squish it down a little bit.
That has to do with the projection and the fact that we're not right on the equator.
But it's done a very, very good job of filling that point in.
So now we're gonna just do our fourth corner,
just to see how good of a job it does. This is just our double checking here.
So I'm gonna find that other 40 on the west side of the map. It’s gonna probably
guess extremely well on my coordinates so I'm not gonna worry about checking them.
I'm gonna click once, Input DMS.
Okay, so in this case it should be probably 86 degrees, 15 minutes,
0 seconds West, and that makes sense, it just was a little bit off.
15 minutes, 0 seconds.
And 41, 40, 0, so it's just a hair off there.
And go ahead and hit OK.
So it doesn't really move it at all.
You can see that there's a little bit of difference between them.
But the map in general is now where it's supposed to be, you see my coordinates
are moving about what I would expect as I'm moving across South Bend, Indiana.
And I would say I'm probably ready to check the error and then
finalize the georeferencing on this image.
Now to check the error or delete a point if I made a mistake, in my Georeferencing
toolbar up here, I would use this link table, View Link Table.
So first, I want to look at my error. You can see that all of the residuals here and
the total RMS error are all in something to the negative fifth power exponentially.
So these are really, really, really small numbers.
This is good, this is exactly what I want.
If you see anything that's much bigger than this,
then you probably don't want to do it.
If I was very unhappy with that fourth point and I wanted to delete it,
if I had made a mistake or something, I can always go in here.
I can either edit the points, the numbers themselves,
if I wanted to fix that mistake, or I could simply delete a point by clicking
the point, highlighting it, and then this middle button right here.
I'm not gonna do it at the moment, just because I kinda do want all of these
points, but that's how you would go back and delete one.
Now once you're done, in this case I'm happy with it,
it seems like it's where it should be, everything is ready to go.
I'm gonna choose Georeferencing, the drop-down for it, and
I have a couple of different things here.
If I wanted to change my transformation technique to use a higher order
polynomial, if I had more points I could do this.
I could put either a second or third ordered polynomial.
In this case I'm not going to.
First order in affine is what we want to do.
We can either choose to update Georeferencing,
what this is gonna do is it's gonna attach something onto that .jpeg file
that just displays it the way that it should.
It knows where it is, it saves it as a separate file, and it's good to go.
Or I can choose Rectify, which creates an entirely new file that has been projected.
For ease and speed with these,
we're gonna just work with Update Georeferencing for now.
So go ahead and choose Update Georeferencing.
And that's been now made permanent.
We now have a permanent version of it,
you see we've lost all of our other options, we're ready to go.
So we wanna basically repeat the entire process with the second half of
the image now.
Once they've been put together, it's much easier for us to mosaic them together into
one full image of South Bend, of the quad sheet for South Bend.
So the very first thing I wanna do is choose to switch over in
the Georeferencing job down to South Bend east quad two.
Then I'm gonna turn off one and turn on two.
I can't see it yet, I want to right-click and go to Zoom to Layer.
So I have the same image.
I have pretty much a little bit of crossover spot.
I've got the top two corners of the map, and
probably some other parts that are in here as well.
So I already know the coordinates system is the same,
I'm going to zoom in on the top corner here.
Now USGS quad sheets are almost always lined up correctly, with
a coordinate on the very northern corners, as well as the very southern corners.
But Northern Indiana, where we are at Notre Dame,
we actually hit the edge of the state, before we finish this quad sheet.
And it ends at the difference between St.
Joseph County in Indiana and Berrien County in Michigan.
So the corner that we would normally have would be up higher.
So this is actually the corner right here.
This line, right here, is 86 degrees, 15 minutes, 0 seconds West longitude.
And this is 41 degrees, 45 seconds, 0, or 45 minutes,
0 seconds, North latitude.
So, if we're right there, and then we click right here, this is our coordinate.
So this is our first coordinate.
We've done one click on it, we're gonna right-click.
Input DMS of longitude and latitude.
Again, our longitude is going to be 86 degrees, 15 minutes,
0 seconds West.
Our longitude is 41 degrees, 45 minutes, 0 seconds North.
Now, it's gonna move when I hit OK again.
In this case it doesn't disappear just because of where it is, but it's still,
the coordinates do not line up properly.
So I'm gonna zoom back out and I'm going to find the other corner over here.
Now the same as before, you're going to want to find where those lines cross over.
And this one is going to be 86 degrees,
7 minutes 30 seconds, West longitude.
41 degrees, 45 minutes, 0 seconds, North latitude.
So I've got my two, clicked once, right-click Input DMS.
We're going to do 86
degrees 7, 30,
West and 41, 45, 0 North.
So now I want to right-click Zoom to Layer.
It's in the right spot but we still have a problem with our,
we still need a third and a forth point to really finish it off.
So, again, I'm gonna zoom in.
I've got my coordinate up there.
I have one right here, too.
In this case,
this is gonna be 41 degrees, 42 minutes, 30 seconds.
You know that because the other coordinate up here.
It just has not repeated the degrees of it,
because it assumes that you know that it's 41.
And in my west edge of the map is the same coordinate, so let me put my three.
Input DMS, remember it was 86, 15,
0 West. In this case it's actually 41, 42, 30.
So it's just a little bit off there.
Hit OK. Just squishes it down a little bit.
So I'm gonna zoom out a little.
We're gonna test to that fourth point again over here.
Click, right-click, Input DMS.
It’s gonna guess for me.
86, 7, 30.
41, 42, 30.
So you can see it's moved just a little bit.
There is just a little difference there.
So now before I finalize my georeferencing on this one,
let's just zoom all the way out,
see how they look next to each other.
They look pretty good. We turned both of them on, we can see they line up properly,
They fit into the same space correctly.
We're ready to go.
So I'm going to go ahead and hit Georeferencing,
Update Georeferencing again.
So now I have my two parts of my map ready to
be manipulated into one piece of a map now.
So if I put one on top, you can see that one doesn't have that black line in it.
You're gonna want to, for part of the assignment, to zoom in on this border and
just see if you see any things that don't line up.
And it's common that things will line up maybe a pixel off or so.
But if you’ve got roads that are just really are super jagged between them,
then you might have a problem.
So we're ready to do the mosaic here.
It's actually pretty simple to do.
If your Image Analysis window is not up the way mine is,
this is a sort of legacy from our raster demonstration,
you're going to go to Windows, Image Analysis to turn it on.
And to mosaic two images together,
in ArcGIS, all we have to do is to select both of them in the Image Analysis window.
So the top part here.
And then our Mosaic command is going to be this right here.
Now we have a bunch of options for what we want to do in the drop-down.
Blend would mix the two values,
it would take an average of the two values of any area that overlaps.
Last is gonna take the bottom one.
First is going to take the top one.
Minimum, maximum, Mean, Sum, these are all sort
of different ways of figuring what to do with areas that overlap.
If you have your number one on top of your number two, well,
the number one is the one you want to take.
So, in this case we would want to use First.
So, its going to go for the one that's on first.
So, choose First.
And then, you're going to click this Mosaic button right here which
is right next to where it says First.
So, it'll run for a second.
Its going to look like not a lot happens.
But, actually what’s happened, is if we turn off the other layers,
we just have this one new mosaic, one that's in place there.
Now this is a temporary file.
This is not saved permanently anywhere yet, so we do want to go ahead and
save it permanently.
And then we'll work a little bit more on here.
So let's go ahead and choose it over here, in Image Analysis, the mosaic one.
And then it's gonna be this button right here, saves it permanently.
So click that, Export.
It's gonna fill everything in properly for you.
Do remember that this is one of those situations where it's asking you for
the location of the folders separate from the name of the file.
So, we're going to make sure that this is pointed at the folder for demo four.
So, go into your GIS folder, find the demo four data.
Highlight it like this.
Don't double-click on it.
And then, hit Add.
And I'm gonna call this Mosaic South Bend Quad.
And I'm just gonna slightly change the name.
We don't need the one anymore in there.
And I wanna stress that this is in latitude and longitude because the next
thing we're going to do is to re-project, to create a projected image out of this.
So we're gonna go ahead and hit Save.
It's gonna ask you about this.
You can say Yes or No.
Yes, it'll make the file a little bit larger, but
there's no real reason not to do it.
So now we have something that we've referenced this image to a latitude and
longitude system.
But what we want to be able to do is convert it into a projected system,
particularly convert it into a UTM-based projected system just like we talked about
in the lecture for this module.
So this is actually a fairly simple process to do.
Once it's stopped running here, we're just going to use a command in the Arc toolbox,
which is this large number of different tools that we can run.
So now that it's saved, and we've added it back in,
we have our Mosaic South Bend East Lat Long.
We don't need the temporary one anymore.
We can right-click and remove it.
And what we are going to do is load up this Arc toolbox button right here.
So go ahead and click on that.
Yours may arrive docked, it may arrive floating in space.
Regardless, what we are looking for
in here is we want to go into Data Management.
Projections and Transformations.
Raster and Project Raster.
And what this will allow us to do is take this latitude and
longitude image and convert it into a UTM-based projected image.
So once it's finished running here,
this is our very standard Arc toolbox kind of tool thing.
Got our name up here.
We can choose the Input either in drop- down here or by dragging it over.
It should scan through the file and figure out what the input coordinate system is.
It is the geographic coordinate system, GCS North American 1927.
We're gonna give it a more intelligent output location than this default.
So we're gonna send it into our demo four folder.
We're gonna call it Mosaic South Bend East UTM.
We're gonna choose our output coordinate system by clicking on this
button right here.
We're gonna go through Projected
UTM WGS 1984, so we're converting between datums as well.
Northern Hemisphere, and Indiana is in zone 16 North.
If you're doing this for any other image somewhere else in the US or
elsewhere in the world, you need to know what UTM zone you're working with first.
There's some resources available online to find what that is.
So choose OK, and
you can see it automatically filled in that geographic transformation for us,
so it's going to automatically know what the datum transformation it should use is.
So once that's in place, go ahead and hit OK.
It's going to create a copy of that image.
It's going to run for a minute or two to do that.
Then we're going to end up with an image that is now
georeferenced correctly to real world coordinates.
And has been reprojected into UTM, which is the coordinate system,
the datum and projection that we want to use throughout the rest of these modules.
So once that Project Raster tool is finished running,
you should see the new layer, the Mosaic South Bend East UTM has been added in.
It shouldn't really look all that much different to you at the moment.
It's still in the same coordinate system in the map documents so it's going to
display exactly the same as it would with that geographic coordinate system, but
it's innately in the file now that it should be in
the UTM Zone 16 North Projected coordinate system.
Now, this is really important for
following along with this particular module.
At this point, we want to start a new map document so
that we're in the correct coordinate system.
And this is because the next stage is going to be to georeference that file,
that aerial image from one image to another.
So go ahead and choose a new map document here.
You can save the old one if you want to,
if you think you might need to go back a step or two.
But when you're ready to, just choose a new Blank Map document.
And then we're gonna add back in, and this needs to be the first thing you
add back in, that Mosaic South Bend East UTM layer.
So now you can see that it's displaying it a little bit different.
This is because of the projection.
And what you probably noticed right away is that this is now in meters down
here and these are really big numbers.
This is very indicative of the UTM system.
So once we have this in place, we're gonna go ahead and add in the last thing we
wanna do, which is that aerial image, that 1998 aerial image of Notre Dame campus.
So hit that and choose Add.
It's gonna calculate some of the statistics, create a histogram for it,
all the things that usually happen when we bring in an un-georeferenced raster image.
And it's gonna, when it finally displays,
it's gonna display off someplace that isn't overlapping.
Because it doesn't know where it is in space,
it's going to stick it down at the equator.
And again it's going to give us this unknown spatial reference.
So hit OK, and then we're just going to simply zoom to that layer.
So what we want to do is we wanna find things in common between this image and
the one that we have from our mosaic quad sheet there.
So first thing, make sure that your geo- referencing is pointing at the aerial
image, you don't want to un-geo- reference your mosaic UTM image.
And let's zoom in on, say, Notre Dame campus, cause I imagine we'll probably be
able to find things like the Notre Dame Stadium between two different images.
So we're gonna choose Add Control Point.
And just go for the very, very center if it.
This is not a phenomenal point to use,
but it's a decent enough one to start with.
Now, this time, instead of just right-clicking and
entering coordinates, we don't know the coordinates for that spot.
So what we wanna do instead is zoom back to the other layer with that line still
active, so right-click on it, go to Zoom to Layer, and we're gonna zoom in
(I just happen to know that this is Notre Dame campus around here)
until we see the stadium and
we're gonna to get it in the middle of it again as it renders here.
So it's going to move it to the right spot, and now we just need
to find a few other points that we have in common between them.
Now, if you turn them back off and on, you can see where the things are likely to be.
So if you see this intersection right here,
that's pretty likely to be that intersection right there.
We're getting a little bit better, things are still not lining up perfectly.
We do run into a little bit of a problem that the lines
actually leave the edge of the map.
Let's look at something kind of down near the river.
Using rivers is a phenomenally bad idea because they tend to move around a lot.
But what doesn't tend to move around nearly so
much are bridges associated with rivers.
So you see that there's this little on-ramp right here.
So I'm gonna get where that on-ramp hits the main road.
And then that's the same on-ramp right there, as it goes right there.
So now we've moved things around a lot.
They're lining up pretty well.
This would be a great time to play around with the Flicker and
Swipe tools that we talked about before. So if we wanted to use, say, Flicker.
Sorry, that's Zoomed to Raster resolution.
If we wanted to use the Flicker tool here,
we can see that it's flashing back and forth.
We can sort of look at particular spots and see what they might look like.
If they line up between the maps.
They look to be doing a fairly decent job.
I may want to get a third or fourth point in here.
I may even want to remove some of the initial ones that I had.
So let's zoom back out, and
we'll try to find another spot that might be good to use.
So that looks pretty good there, you can see the actual building footprints,
In some cases things are going to have changed a little bit.
But I think we can probably find a fourth point down in here someplace.
Yeah, I would say that that spot right there is probably a pretty decent one.
And I'm just gonna turn off the other one, so that I can spot it and come back out.
So now I have these lined up fairly well,
I'm pretty confident in the points.
If I look at my link table again, I can see my RMS there is about ten meters.
That's about as high as you want it to be.
If I wanted to, perhaps deleting that first point,
that really kind of imprecise one I did in the middle of the football field.
Let's see what happens if I do that.
Do they look like they still line up fairly well?
They do, but let's find another point somewhere on campus, so
we have this kind of area, as well.
Here I'm just gonna go back to my Swipe tool, see if I can't
spot something else in here that I might wanna use.
This is what the process of georeferencing these images tends to
look like.
You go back and forth pretty regularly.
You're sort of trying to decide what points to use at any given moment,
to kind of get it to line up as perfectly as possible.
Now actually I'm going to avoid in here,
because they've actually changed quite a lot of these roads.
But I would guess that that point right there
probably at least roughly confers to that point right there.
Let's see, my RMS there is about the same.
So I'm probably about as confident as I can be with this particular image.
So when I'm ready to go, I'm gonna choose Georeferencing.
I'm going to choose Update Georeferencing.
And now my aerial image is georeferenced to that UTM, the WGS 1984,
UTM zone 16 North coordinate system.
So what we've gone over in this module is how to georeference a scanned image,
how to mosaic them together,
how to re-project something from one coordinate system into another,
and also how to georeference something that doesn't have coordinates already
printed on it.
So I would work through the assignment for this module.
Please don't hesitate to contact me with any questions.