The Battle of Gettysburg took place 150 years ago, and is considered by many to be the turning point of the Civil War. By marrying the magic of cartography and technology, we can put ourselves in the places of General George Meade of the Union army and Confederate general Robert E. Lee as they planned their respective movements around the limitations of the era and the terrain. Anne Kelly Knowles explains the map features.
Our team, which includes myself, researcher Dan Miller and cartographer Alex Tait, have done just that. Alex recreated the 1863 terrain based on a superb map of the battlefield from 1874 and present-day digital data. Dan and I captured troop positions from historical maps. Our interactive map shows Union and Confederate troop movements over the course of the battle, July 1 – 3, 1863. Panoramic views from strategic viewpoints show what commanders could – and could not – see at decisive moments, and what Union soldiers faced at the beginning of Pickett’s Charge. You will also find “viewshed” maps created with GIS (Geographic Information Systems). These maps show more fully what was hidden from view at those key moments.
The maps are controlled by a timeline, so you can pull up troop positions at different points in the battle. Link -via Kottke
Comments (3)
On a TV, if you illuminate one pixel then illuminate the one next to it, it appears as though the image is moving. If you do the same thing but skip to every second or third pixel, the image appears to be moving faster. Every tenth pixel, the image shoots across the screen. Nothing is actually changing speed; we just see the gap increase.
If you had a laser beam strong enough to be visible after reflecting off the moon, and you moved the beam from one part of the moon to the other, it would take about 2.5 seconds for you to see the beam move on the moon's surface.
That's the amount of time for the beam to reach the moon, and return.
When the person moves the laser, the photons that are currently arriving at the moon do not move.
The photons exiting the laser take over a second to get to the moon, and arrive at the second location.
Take a hose and spray something far from you. Then flick your wrist and aim to another spot on the driveway. It takes a second for the water exiting the hose to catch up to the new target. Same idea.
This guy isn't that smart.