Cost Distance 2 - Cost Distance

this video is the second in a series about using cost distance tools in ArcGIS and the first video we reviewed some basic concepts and then demonstrated the fact that for cost distance you need an underlying grid that I've been calling a cost or a friction grid these are just some examples these were they're the kind of raster that dictates in some instances where you can move right like in this one I said yeah treat yourself like Euclidian distance in all these black areas but I changed everything else - no daddy can't even move through that area or actually where I've given a different value to each cell which is gonna now factor against its distance right in this instance that value is practical it's the time right the amount of time it would take you under minutes per foot to walk or something abstract all right this one's something that's essentially minutes per foot but also has a new element which is uh you know raising the cost in into a crazy degree these areas where where we were saying that my ex has the highest possibility of seeing Li so in order to run cost distance you find it under the spatial analyst cost distance or so our distance cost distance toolbar and so if you open it up you notice a couple things always wants to begin with a source data right anytime something tells you raster or feature remember that means it could be either right so this could be a raster this could be a feature same thing as euclidean distance you know this is often best thought of as your source your origin point you know but you know your distance to something you know in many cases is the same as its distance to you there's obviously some you know differences in that with all my streets and such so you can think of this as a destination but it's good to think of it also as like a source your origin this is where you're gonna measure your distance from right you can have multiple sources but for now we're gonna keep it easy with one and the only real difference between this and euclidean distance is that it needs a cost raster right you will create your own cost raster's I can't teach you how to create those right for example how I did though just you know do you have an idea I created a lookup field and then I gave the values I wanted to each one right so for ones where I wanted to just be able to pass you know I gave them values of 1 and then whatever I wanted to be no data right I just didn't necessarily select and then just use the lookup tool did the same thing to create the walk time one by putting a value here but again it's totally up to you how you're gonna create those I just want to show you once you've created them how you're essentially gonna use them so let's start with the simple one right the the one that sort of you know emulates Euclidean distance but it just removes the streets so you can't walk on them you gotta have these like narrow paths that you cross here so you drag that in right that's your underlying cost raster that dictates essentially the toll or the cost of the friction for each grid I've already kind of created each of these for us so I'm just gonna name this one example real quick just so you can see it be created and then you know I walk through the other ones that I made as well and the only real other difference here is this backlink raster it's I think it's really good to just get it done and get it out of the way to create it as I'll show in a second the distance raster tells you how far you are in whatever unit your cost is in from the source the back link tells you how to get there so it's essentially like a directions so to look a lot like a Euclidean direction but it's always good I think to create those you know just so we can see what they look like so I'll call it example DL and then you have these pretty cool addition you know only those of you who are using 10 4 and above will see this you know wasn't originally on one of my videos back in the day but I've updated it because they're pretty cool so these are just sort of like multipliers or characteristics that you're going to apply to your source and I'm gonna have a separate video that shows these one by one but let's just you know talk about them each real quick the multiplier simply would be like if let's say I had you know multiple things maybe I was doing maybe I was doing this one maybe I had like multiple ones here that I wanted to measure my distance from and I just maybe put like a multiplier value in the field like one for this point five for this two for this well it would simply multiply that multiplier by the costs right so you know the way I like to think about these is this one allows me to determine that this is me and you know this is somebody who's wearing like a cast on their foot right they would be slower than me they would walk maybe at a factor that's like two times slower than me so I should make sure I add that multiplier to them start cost metaphor I would often use two this is like a hospital or a health center right so imagine that these are three health centers right here and you wanted to measure your distance from them which one you could get to first right well you could measure the distance which when you get to first but once you get there you're also probably gonna have to wait in line right if it's if it's a health clinic to be seen so what if you could do a cool little equation that took into account not only how far does it take to get to each one but also once you get there how much extra time you'd be waiting so that's like start cost it actually takes a fixed rate or a variable cost and applies it at the beginning of each a cumulative cost is essentially like I would say like a my grandfather who the longer he walks the more tired he's going to get right so that's what that does here it acts very similar to the multiplier but it's a multiplier that increases in intensity as time goes on and finally capacity is very similar up here to maximum distance but whereas maximum distance would make it uniform for everybody capacity gives you the opportunity to say like I just I stopped after ten minutes I stopped after two I stopped after 15 degrees I stopped after fifty however you want so we'll do another video for those you know just want you to be aware what they are but for now let's just run this we'll take a second to do its thing alright we get two kind of outputs here let's do the less confusing one first right and so looks very similar to Euclidean distance and I you know created them all here that I'm gonna show you in a second you know so we're not gonna focus on this one for too long but right there's a source it began here and it simply measures its distance out right you don't necessarily have this kind of neat you know radial thing anymore almost because you're being pushed in a sense here right so you can cross are you being pushed in a sense here so you could cross you can also cross there all right so that's that's why you're seeing these kind of angular things here that it's a little bit less distance in certain areas because you're being pushed towards certain areas because you can't walk on the street a backlink looks chaotic but it's super logical you know there are eight cells around you or we could open the presentation just as an example and imagine you're in the middle here and what this is saying is like in order to get to the source from my cell which direction would I have to go would I have to go right lower right down lower left left blah blah blah blah blah and that's calculated you know very similar to how flow accumulation works or how flow Direction works if you imagine water moving down a mountain just pretend that this is also a surface except it's not a surface of a mountain it's a surface of travel time and the largest and highest peak of your travel time is when you're farthest away from your source which would be kind of your lowest point and so if you were here theoretically if I wanted to flow my way back to the source I would simply for each cell be looking at which cell around me is the lowest and following that value I think my screen protector turned off so I'm just gonna disable that for a second so it's a little bit cleaner to see all right so I'm gonna delete these two right now because like I said I already created examples for each one and I'll uh turn those on right now so we can actually see them alright if you remember I created one that was removing the streets one that was only the pathways right so you can't go in the buildings you can't go on the land another that you could go anywhere but the streets but I gave you a time a time in minutes right so it's fewer minutes to be able to walk on these paths it's more minutes to walk on buildings it's the most minutes to walk on grass and finally I did one very similar to that but that got even more abstract by adding like an element of where my ex could see me right my ex could see me in these blue areas and that's why the cost is the highest so let's take a look at each one right so first there's the Euclidean distance right that's one always easier to measure I started at my source Euclidean distance brought me outward in a super radial fashion very easy we've got all of them stretched to the same thing between 0 and 415 so the next one on top of that was if I couldn't walk on the streets and it looks somewhat similar except as you see there you go right any of the areas that were no data in my input or no data on my output and I can't walk on the streets and then finally the pads even coming more funky now it's a little difficult to visually be able to see the difference here but let's actually analytically test the difference right so if I just scrolled into here and I grabbed my pixel inspector and let's say first thing I'll pick is Euclidean and I'm just gonna tap an area here to get to that area Euclidean distance as the crow flies would be approximately sixteen hundred and sixty-four feet if I had removed the streets it would be 1818 feets right so the removal of the streets magic I could just still fly anywhere else but couldn't go on the streets adds almost another 200 now I can't go on land or buildings or streets and it's way higher right it's 2,100 you know you can kind of see that if we compare the two right that's path on top of Euclidean distance right they're using the same scale and as you can see it's a much larger thing gets even more interesting when you start to look at the others right so time for example like what I did for my symbology of time here is actually broken into minute segments right so anything here would take two minutes four minutes right within six minutes to get to any of these spots would take eight minutes you know to get to this one would take between eight and ten ten to twelve and so on and so forth and again that worked because the cost raster charges you a tax right to walk on each path and that tax for a pathway right is cheaper than it is for here which is why you see certain areas where you'd have to walk on the grass or walk away from kind of the pads or the easy areas or a little bit more you know costly to actually have to walk across I'm gonna turn the display on here just to make that a bit a little bit easier to see right farther to be able to do it than to walk directly on the path you can really clearly see that right here right as I continue the path it kind of keeps that open direction following the pads and becomes a lot more costly going out here and this broadly most you know emblematic if I were to show you the cost distance from my x1 right remember again my x1 where these were where my X's were or mostly hang out and then this is the areas in red where they could see me using invisibility and so assuming those things this is what my cost distance would look like my X now again this was time distance distance distance this one's funky it's a little bit more abstract what we need to know here is that the low values are definitely lower than the high and that helps you understand that it actually would feel that much more oppressive in terms of distance there is so much greater risk there is so much greater cost in going this small distance then there isn't going this entire way around because those are areas of high X right high X high ACK ix hi xix so that's cost distance and as I said before all it takes is that input of a cost raster right so for each one if I wanted to create the walk time one I would just drag in the walk time I wanted to create the X friction I would just walk in the X fiction the kind of art to using cost distance a lot of the time is creating those friction grids right those cost grids in some instances perhaps you're simply removing something right I'm removing roads but everything else I still charge one right a factor of one so I'm saying just accumulate distance but don't go on the roads it's the same thing with the path but a little bit more complex sometimes you're actually ascribing totally new values right so using the lookup tool from my original grid I took a value that was minutes right minutes per foot that I felt it would take to walk that was the speed minutes per foot and I ascribed different ones for different types of land cover that I might move over then I took some which is totally different it's not time it's not distance it's kind of a bit of both but it's also just weird and abstract it says it feels so much more intense there's so much greater risk there's so much greater cost walking in an area where my ex could potentially see me so when I model the cost distance make that area seem much more restrictive than the areas around it so that's cost distance very easy to run but the next video we're actually gonna introduce cost path right which is gonna take not only the distance but these backlinks right these things I was talking about before that are the directions right that you would have to take and we're gonna use those to actually be able to see a path that you would take to get from one point to another

Channel: Shea O'Neill

Views: 4,741

Rating: 4.6190476 out of 5

Keywords: ArcGIS, Cost Distance, Cost

Id: BOra2UzR-kk

Length: 15min 10sec (910 seconds)

Published: Sun Feb 26 2017