Maps Skills : Using Scale (2nd Ed, 1988)

[Music] thank you [Music] there he is Explorer Lance Boulder on an island and is he ever in trouble because also on the island is this a volcano ready to erupt at any moment how will Lance get off the island in time how will he ever wait a minute volcano nobody said anything about a volcano get me out of here but you're the hero aren't you going to save yourself save myself are you kidding I can't even find my boat that's the only way to get off the island you know where it is don't you you can find your boat for yourself all you have to do is use your head well could you give me something that would let me see the island since I don't know where I am on it I sure can one way of seeing the whole island is by looking at a photograph taken from high above the island an aerial photograph an aerial photograph shows everything you would see if you were really high in the air looking down boats in the water large rocks even clouds if there are any but I can't see anything in this picture because of the clouds well there is something simpler that you could use instead of a photograph a map a map doesn't show everything a map uses symbols to show the locations of only some of the real things shown in the photograph like mountains or rivers or a lake but of course you have many choices which map would you like first you can have any you want well I guess I want one of the whole island here it comes look out I'm on the wrong side of the map can you put me on top instead but this map is enormous it must be as big as the whole island oh it is as big as the island exactly the same size in fact but I can't see any more on this map than I could see on the island does a map have to be this big a map can be any size like the map you have now it could be the same size as the place it's a map of in that case any distance on the map would be the same as the distance it represents on the place it would yes for instance suppose you measured the distance on this map between say the volcano that's here and this Lake and found that it was so many kilometers or miles or whatever you'd know that the distance on the island between those two places was the same number of kilometers or miles or whatever if this is one mile this is also one mile this relationship tells us the scale of the map one to one which can be written like this but I can't use this map it's too big well suppose we shrink it oh now the map is on a different scale the island on the map is exactly half the size of the real Island so any distance between places that we measure on the map stands for twice that distance on the island any one unit of length on the map inch foot or whatever equals two of the same units on the island now the scale of the map is one to two if we change the scale to one to four [Music] now any distance between two places that you measure on the map the distance all the way across the island for instance stands for a distance four times as long on the real Island but I can't use a map with a one to four scale why don't you give me a map with a scale I can use all right I'll change the scale and I'll also change the size how's this that's more like it there's the volcano and this says you are here so this x must be where I am and there's my boat terrific what is the scale of this map anyway it doesn't say 1 to 63 360. one to sixty three thousand three hundred sixty what's that all about well it just means that one inch or any unit on the map equals 63 360 of the same units on the island and since it so happens that there are 63 360 inches in a mile that means that one inch on the map represents one mile on the island very good with this scale you could use any units so no units were written in now we have a different way of showing scale with two different units that are written in one inch represents one mile and I think I know how to use that if I measure the distance in inches between any two points on the map I know that the distance between those same two points on the island is the same number of miles that's right very good so how far do you have to go I'll measure on the map I'm exactly four inches from the boat so I must really be four miles from it four miles that would take me about one hour I don't think I have an hour I'll help you which direction do you need to go the map shows that if I go directly through this pass I'll be going toward the boat the pass is over that way so that's the direction I need to go hang on now where am I you're part way there look at your map oh good there I am but I'm getting worried how far do I still have to go I know that the scale of this map is one inch stands for one mile so I need to measure on the map how many inches I am from the boat but I can't measure I lost my ruler there's another way of showing scale that will help you measure even without a ruler a bar scale it indicates exactly the same scale that the other two statements do but in a different way a bar scale can be made in any units but this one represents miles so each segment on it stands for one mile on the real Island you can use it to measure one mile or two miles or three or four or any number of miles to use it you measure the distance on the map with anything and then compare that distance with the length of the bar if this is the distance from me to the boat on the map then there must be two and a half miles to go right and here's something you can use to check your answer the ruler you lost it shows you've got two and a half inches to go on the map or two and a half miles on the island check now that you know how far you need to go it might be a good idea to recheck the direction to go well let's see I'm here at the X and the boat is that way so to get to the boat I still need to go through that pass I need to go that way correct and because you've learned so much I'll help you out again ready oh no I'm in the middle of a canyon the real world isn't flat like a map you know now I can't go in a straight line winding through a canyon will take me a lot longer how far do you have to go I don't know I can barely see the canyon on this map I need a map with a different scale a map of just this area here it is good now I can see more detail that's where I am and that's where I'm going now I just measure the path with my ruler hey how can I measure a winding path I can't bend a ruler what could you put down that you can bend I know I can use my shoelace like this [Music] [Music] this tells me that on the map it's this far from me to the boat that's 10 inches so I must be 10 miles from the boat that's farther than when I started did you look at the scale what oh I forgot we changed the scale on this map one inch doesn't represent a mile one inch stands for 25 feet so a distance of 10 inches stands for only 10 times 25 feet or 250 feet I've got time to go that far I think and because you've solved another problem I'll make it easy terrific thanks if it hadn't been for you helping me to understand scale I would have been in big trouble now I've got to get out of here [Music] [Music] thank you [Music] foreign [Music]