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  • I'm a geographer at Middlebury College,

  • and I use digital technologies

  • to reimagine the past.

  • I want to take you to Gettysburg, Pennsylvania,

  • July 1, 1863,

  • we're right in the middle of the Civil War.

  • >From the northwest,

  • the Confederate forces

  • under Robert E. Lee,

  • and from the southeast,

  • the Union forces under George Meade,

  • converge at this place

  • more or less by chance.

  • They didn't plan to fight here.

  • But the Battle of Gettysburg turns out

  • to be the turning point of the Civil War.

  • Now, Robert E. Lee is probably

  • the most famous American general,

  • widely respected.

  • But at Gettysburg,

  • he made some crucial mistakes,

  • probably the most important

  • was in ordering Pickett's Charge.

  • I'm going to show you

  • how I took a new look at Pickett's Charge

  • with historical maps and GIS.

  • My key map was this extraordinary thing,

  • 12 feet by 13 feet,

  • in the vault of treasures at the National Archives.

  • Here are some of my students at Middlebury

  • to give you a sense of that scale.

  • It was recompiled into a finished map

  • the size of a large poster.

  • You can see the layout of the town of Gettysburg,

  • you see the undulating shape of the terrain.

  • If you look at other details,

  • you can see forests and orchards and streams and roads.

  • I want you to look at those very fine black lines.

  • Those are called contour lines,

  • and they show the elevation at 4-foot intervals,

  • the most detailed elevation I have ever seen.

  • Now, before I explain this image,

  • I need to tell you a little about GIS.

  • It stands for Geographic Information Systems.

  • It's a kind of software

  • that allows you to map almost anything.

  • You can also use it to do terrain analysis.

  • For example, if you're building a ski resort,

  • and you want people to get off the lift

  • and have the most spectacular view possible,

  • you use viewshed analysis

  • that shows you what you can see

  • from a certain point on the terrain.

  • I used that to place myself digitally

  • in the footsteps of Robert E. Lee,

  • to ask, 'What could he see?'

  • and 'What could he not see?'

  • that might have influenced his command decisions.

  • Now, back to these contour lines.

  • This is the best elevation data that I could find.

  • I traced all of the lines,

  • you see in the black and white drawings,

  • some of those lines,

  • stitched them together,

  • gave them elevation values,

  • and then transformed it, within the GIS program,

  • into a continuous terrain.

  • This is a simulation of the ground of the battlefield.

  • Now, I'm ready to place myself in Lee's boots

  • and ask what he could see.

  • The particular moment I want to look at

  • is that battle I mentioned, Pickett's Charge.

  • Lee makes a crucial decision

  • on the morning of the third day,

  • this is July 3rd, 1863,

  • the fighting on the previous two days has been fierce.

  • It's gone back and forth,

  • neither side has a clear advantage.

  • Lee goes down to the bottom of the field,

  • we know this,

  • here's my gorgeous source map again

  • and watch the red circle appear.

  • He goes to the southern end of the battlefield

  • at about 8:00 in the morning

  • with his binoculars

  • and looks through them

  • to figure out where to attack the Union line,

  • where are they most vulnerable.

  • Now, in this next image,

  • I'm going to show you the GIS process

  • called viewshed analysis,

  • along with Lee's line of sight

  • in that sort of reddish cone

  • is the direction we think he was looking.

  • Viewshed analysis, remember, tells me what I can see

  • and what I can't see

  • from a certain point,

  • so in this map,

  • the grey area is what Lee couldn't see.

  • The clear area, where you see that historic map coming through,

  • is what he could've definitely seen.

  • Notice how much of the right side of the map is in grey.

  • Now, we add another crucial piece of information.

  • Someone named John Bachelder,

  • a landscape painter from New Hampshire,

  • went down to the battlefield

  • as soon as he heard about the fight,

  • in order to document where troops had been

  • and to try to paint the battle.

  • He ended up getting $10,000 from Congress

  • in order to document troop positions

  • down to the half hour.

  • He produced 24 maps

  • that we also digitized

  • and brought into the GIS.

  • And this next map shows that troop position information;

  • it's crucial for understanding

  • what Lee could and what he couldn't see.

  • Now, if you look closely at this map,

  • you might be able to see

  • kind of the middle

  • is a black oval around an area that's relatively clear.

  • The blue markings in that black oval

  • are Union troops that I'm definitely sure that Lee could see.

  • But if you look to the right of that,

  • you'll see an awful lot of blue markings.

  • Those are Union troops in the shadows.

  • Now, we know that on the night before Lee's reconnaissance

  • so, the night of July 2nd, he sent out scouts.

  • Of course, he wanted to know where the federal troops were.

  • But quite astonishingly,

  • we have no explanation for this.

  • The scouts came back saying,

  • 'Don't worry, General Lee.

  • We didn't see any troops to the east,'

  • in your map to the right,

  • 'of the Roundtops, some really big hills.'

  • We don't know if they got drunk or fell asleep,

  • but they didn't see almost a third of the Union army.

  • So Lee is blind from his scouts,

  • and from his viewpoint, he's also blind.

  • He decides to attack

  • what he thinks is the weak middle of the Union line,

  • not knowing about where the rest of the troops are.

  • So if you look in the middle of this image,

  • there's a gap in the Union line

  • from where the blue soldiers

  • are at the north of the battlefield and at the south.

  • So let me now play out,

  • using these troop positions,

  • Pickett's Charge.

  • The Confederate soldiers are lined up

  • on the west side of the battlefield,

  • standing under the trees.

  • 18,000 men who first begin to walk and then trot

  • and then run across open farm fields

  • with their rifles leveled at the federal line.

  • Now, the Union army has about 15-20 minutes to organize itself.

  • They see that the Confederates are converging

  • on the middle of their line,

  • and what do they do?

  • The blue arrow here, representing movement of the Union troops,

  • they pull their troops toward that weak center,

  • and let me show you how they were able

  • to concentrate those men in a remarkably short period of time.

  • Lee didn't know that the Union could've done this.

  • You see now, they're standing like a wall,

  • ready to receive the Confederate assault,

  • which happens between 1:30 and about 2:00, 2:30 in the afternoon.

  • There is tremendously fierce fighting,

  • hand-to-hand combat.

  • Now these blue lines,

  • coming in between 2-2:30 in the afternoon,

  • are pulling more reserves, more reinforcements,

  • to that weak center of the Union line.

  • What happens?

  • The Union soliders drive the Confederates off.

  • Lee rides out, among his men, at 3:00 in the afternoon,

  • saying, 'I'm sorry. It's my fault. It's my fault.'

  • This story of sight has been a missing part

  • of the Battle of Gettysburg.

  • Here's their retreat.

  • Historians have not been previously able

  • to figure out what he could and couldn't see.

  • I think it helps explain his decision.

  • Why? Because from his point of view,

  • the federals were very weak.

  • He was attacking at the logical place,

  • but without full knowledge,

  • he set his men out for a dreadful defeat.

  • Now, there's one more piece to this story.

  • Last summer was the 150th anniversary

  • of the Battle of Gettysburg.

  • And I was able to work with a 3D animator,

  • so we were able to use the GIS information

  • to render the terrain issue as you see it here.

  • And my closing story is about how sight helped the other side.

  • A federal general named GK Warren

  • stood in the spot that this panoramic view is showing you,

  • looking out over the battlefield.

  • And at a key moment on day two,

  • he was able to see on the far horizon

  • Confederate soldiers emerging out of the trees

  • who were about to attack Little Roundtop.

  • He called in reinforcements just in time

  • and saved the day for the Union,

  • setting the stage for the Union almost-victory on day three.

  • So, I hope that all of you who are so gifted

  • with digital technologies

  • will begin to think about how you can use them for history.

  • It can be amazing.

  • Thank you.

I'm a geographer at Middlebury College,

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【TED-Ed】A digital reimagining of Gettysburg - Anne Knowles

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    稲葉白兎 posted on 2015/04/26
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