 So now, here's a little bit of a review of coordinates, latitude and longitude. And I'm primarily using this for my online lab students just to give them a quick overview to make sure they're on the right track before they start their lab. So we start with the definitions. And I find that the most common problem here is students flipping these two definitions. So latitude is the one that's north or south of the equator, and longitude is east or west of the prime meridian. Those are the definition in words. But what we really want to see is those on the globe in terms of a picture. So here's an example. If I look at the globe, and I mark my equator here on the globe, then each one of the latitude lines, which is also called a parallel, is parallel to the equator. And they mark up, are you this far north or this far north? Or are you this far south or this far south, showing you where you are? So these parallel lines of latitude show you how far north or south you are of the equator. And the equator would then be at zero. For longitude, the lines are called meridians. And they go from one pole all the way down to the other pole. The prime meridian is our zero spot. It's a little bit arbitrary, but it's the one that goes through Greenwich, England. And then we measure how far east or west we are of that prime meridian. So these longitude lines go up and down from the north pole to the south pole. But they're measuring how far east or west you are. Now if you look at this on a map, you might see it a couple of different ways, depending on the projection of the map. So again, the latitude lines are going to be these horizontal lines that show how far north or south you are. Whereas the longitude lines, here's the zero line going through England, which is our prime meridian. And then these would be our other meridian showing how far east or west you are. Be aware that when we try to take a round globe and flatten it out, we end up with some issues. So some map projections try to arrange or correct for this, and the longitude lines will actually curve as if this was wrapping around a globe. So on some of the maps, you want your longitude lines to follow the curve versus the straight up and down. And remember, all of this is based on what's happening on a globe, so the curve makes sense for the longitude lines. Now when we talk about hemispheres, the northern hemisphere is everything which is north of the equator, and the southern hemisphere is everything that's south of the equator. So it only deals with latitude. You could be at any longitude and still be in the northern hemisphere. So this blue section shows the northern hemisphere, and down here, the blue section shows the southern hemisphere. In a similar way, the eastern and western hemispheres are dealing with longitude. So everything that's east of the prime meridian or everything that's west of the prime meridian. And that's how we can break it down into hemispheres using either the latitude or the longitude. Now when you have your actual coordinates of a location, latitudes have to have a number and north or south. Longitudes must have a number and east or west. So for example, 33 north 81 west is in South Carolina, and the north is the latitude, and the west is the longitude. And the reason you have to list the north or south or the east or west is because the same numbers, 33 north and 81 east, is in China, a very different place on the globe. So if you didn't specify it, and you just said 33 81, you have no idea where that is in the world. You don't even know whether they put latitude first or longitude first, because they're just two numbers. It doesn't tell us where we are. So when you actually have to list the coordinates, do not forget the north or south if it's a latitude, and the east or west if it's a longitude. Without those extra pieces of information, your coordinates are not complete. So that's just a review of the coordinate system, latitude and longitude, again primarily for the use of my lab students who are going to be working on an online lab. If you have further questions about it, feel free to contact me.