How to contour (topographic maps)

[Music] hello welcome to giono today I'm going to show you how to contour or for example like the map in front of you how to draw these lines that represent elevation so on our exercise today will be given elevation points then we need to connect the dots so pretty much it's like playing connect the dots for adults so there are some rules that you need to follow to be able to get this done but first just so you know the exercise that I'll be doing in this video today I put a link to in the description so you can download that and follow along alright let's go ahead and get started with some contour rules so you have some background of how to get started so your contour interval is the vertical space between each contour and it must be kept the same throughout the makkal alright and contours will never cross you'll never see that happen because it doesn't make sense because you cannot have two different elevations on the same point in space wouldn't happen contours always close but sometimes they can close off the map so you may not see them close when a contour crosses a stream which we'll do in our exercise today it makes a v-shape pointing upstream so you're gonna need to figure out which way is upstream to be able to make that happen and then most always you're gonna go between a higher and a lower elevation there's one exception to that that I can think of that I'll show you in the exercise today just so you're prepared alright and last if you have a depression or crater you put tick marks on your contour to show that you're going downhill instead of up otherwise it'll look like you're going up to a hilltop so you need to put those tick marks alright so here is your map that we're gonna be working with today this is the exercise so I hope you've downloaded it by now so you can follow along or at least download it later and try it and get the same results so we get today together first thing you want to do is just become familiar with the map so for example what's that blue thing I'm guessing that you can figure that out and you figured it out already that it's a stream right so at some point we're gonna have to cross a stream and we need to figure out which ways up which ways down so how could we figure that out where's the water coming from remember water flows downhill so our higher elevations are over here to the east I say East because I know North is up and then our lower elevations are to the west so I know that it's flowing from east to west or right to left so upstream is going to be to the right or to the east so if we ever cross we're going to need to point up stream alright another thing you need to figure out is your contour interval sometimes it's given to you sometime your teacher just says use a 50 foot contour interval but in our case it's not given to us and in real life it's not given to you so you need to figure it out so let's figure it out let's look for our lowest in our highest elevation and that way we can know exactly what would be an appropriate contour interval based on how much elevation difference we have so our lowest elevation is 300 which we can see over here in the West and then our highest elevation is 930 which we can see down here in the southeast alright so 930 minus 300 is 630 so our total elevation difference is 630 feet so what would be an appropriate contour interval for that probably not like five because then you're gonna have to draw so many lines and it's gonna be so crowded and probably not a hundred because then you're only gonna have six lines and you won't have enough detail so you want to comfort compromise somewhere in there between 25 and 50 in our case for simplicity sake we're gonna go with 50 all right on your contour map you could start anywhere it really doesn't matter some people like to start with the lowest elevation and work their way up some people like to start with the higher and work their way down in my case I just like to start at the bottom of the page but honestly it does not matter and just remember as you're contouring the contours never cross when you cross a stream you have to make a v-shape upstream or a Cattier as I like to say and most always you're going to go between a higher and a lower elevation and then once you're gone once one contour is drawn the contours nearby tend to follow a similar pattern so that's really nice alright let's go ahead and get started with a little bit of contouring let me get my pointer or my pen so you'll have to forgive me it's not going to be a perfect drawing just because of the nature of drawing with a mouse and my drawing abilities combined with that is not gonna help anything so just forgive the errors and drawing and just bear with me on that okay so let's start anywhere let's just maybe start with our 550 so I'm I just I'm gonna draw it off the map because we don't know where it goes that way exactly and remember you always have to go between a lower and a higher number so in this case a lower number is 525 and a higher number is 575 and 550 fits perfectly between there so I can come up and go and hit this other 550 now I gotta be careful here because I can't go up here to the northwest because I would be going between two lower numbers and I can't go this way because I would be going between two higher numbers so I need to go between the 500 and the 575 and hit this other 550 go between the 500 and the 600 hit this other 550 point upstream since we have to cross the stream to get to this 550 and then wrap back around and then come and hit this 550 go between the 500 and the 600 at that 550 go between the 500 and the 625 and we're gonna wrap around I didn't hit the dot perfectly there but that's okay and then just go off the map because we don't know exactly what happens there all right so the next contour we're gonna do if we're working our way to the west is 500 since we're going by 50s so we're gonna go down by 50 and let's connect to our 500 just off off the page connect to that 500 there's a lot of 500s here to help guide us on here we have to cross another stream so just pre-prepared to Cattier across the stream and then hit that 500 and again the really nice thing is once you've got one drawn all of the others tend to follow the same pattern so you're in good shape alright let's go to 450 there we go go between a lower and higher so we went between 400 and 475 hit that 450 come to the 450 and we'll hit this 450 that's gonna follow a similar pattern but it just goes off the map all right let's do 400 that's the next one number Cattier there we go we went between a smaller and a bigger number 350 is the next one let's hit that there we go and then 300 we're just gonna see a little bit of that and there we go so we've completed the map to the west let's work on it to the east where it's a little bit more complicated all right so it looks like our next one up is 600 if we're going since we started at 550 we're gonna go up to 600 we'll just go off the page come between 575 and 700 come between 650 and 575 come between 575 and 700 hit that 600 come between 550 and 650 head that 600 hit that 600 and come off the page all right so before you just go off the page with this 650 look that there's two 650s on the bottom so it looks like we're starting to form a circle which means we're probably as close to a hilltop so we're gonna go ahead and just connect we'll draw it off the page there because we don't have enough room to connect our 650s that way we can connect to those 650 s come between 600 and 700 come between 600 and 700 there hit our 650 come between 600 and 700 and go off the page let's hit our 700 and go all the way around just like before go between 650 and 750 go up to 700 come between 650 and 800 hit ours don't hit that 750 and then go off to your 700 and then I bet we're gonna make a complete loop with this 750 so we'll go between 800 and 700 we'll hit this 750 we'll come up here and hit this 750 come between 700 and 800 and complete the loop and then we'll do the same thing with 800 so we'll come between 750 and 850 come down here between 850 and 750 head that 800 hit that 800 and then hit this 800 so it comes in a full circle now we'll go to this 850 come around come around and then our last circle is gonna be the 900 how do I know that's the last one because 930 is not big enough to give us another contour says that's the highest point on the map we're not gonna have another contour because the next one up would be 950 all right let's start it up here in the northeast corner where it's a little bit more complex so you'll notice that this 550 you remember it came up point it off and wrap back around so that's actually probably what this 600 may be doing is coming up here pointing upstream and coming back and wrapping around to this 600 then we can just connect our six hundreds making sure we're going between a smaller and a bigger number then we will just take it off this screen because we are off the map because we don't see exactly what happens since our map is cut off this is where it gets a little more complex you see a lot of 650s I'm gonna have to draw it a certain way and then I'll show you why that is with another little graphic in just a second but hopefully this helps you understand the idea all right so come between 625 and 675 and connect that 650 but you'll notice there's still three more 650s why and let me show you with just a little demonstration of another graphic okay let me try and make sense of all these 650 s for you so if I draw a profile of a volcano you come up to the top come down into the crater and come down the other side so if you're coming up and you reach 600 feet in elevation or 650 feet in elevation right there and then you come up to the top of it that's 675 and then you come back down to 650 then over here is the same thing right so for that reason since you don't go up another 50 feet you don't have a contour representing this top little Ridge here so you have a contour that's a smaller inner contour and a contour representing the outer six so that's why you have so many 650s they're separated by that 675 all right hopefully that helped you understand why there's gonna be a bigger outer circle in a smaller inner circle so let's go ahead and complete it the 650 it's gonna connects to the couldn't connect to the 650 it's gonna come between 626 75 and then it's just gonna wrap around like that just remember that you've got to have these tick marks there otherwise it's gonna look like it's a hilltop but in fact it's a crater at the top of a volcano I hope this helps you be able to learn how to contour a little bit more the nice thing is if you just follow these rules you'll be able to do this with any map the biggest thing you need to remember is going between that higher and lower elevation if you're following that rule most likely you're going to be on the right track and if you if you find it being a little bit tricky then maybe you've got something a little bit different going on like a crater at the top of a volcano or something along those lines so hopefully this helps you please if it does don't forget to subscribe I really appreciate the support thank you so much for watching you

Channel: Geo Know

Views: 34,023

Keywords: Contour, Topographic maps, how to, rules, elevation, how to contour, making sense of contours, how to draw a contour map, how to draw a topographic map, topo map, contour lines, map and compass, contour map, contour line, topographic map, how to draw contour lines, how to draw contour maps, how to draw contour lines on a topographic map, earth science

Id: yfqmvG5pMi4

Length: 12min 36sec (756 seconds)

Published: Thu Jan 05 2017