ArcGIS Tutorial Extracting Raster Values to Points

so in our map we've seen some kind of large-scale correlation between your rainfall the topography of scotland's however it would be nice to see if this relationship also exists in a sort of finer scale so to be nice if we knew the elevation of each rainfall station now the layer itself doesn't contain that information but of course we do have an elevation model so we could basically just manually zoom in to every point and get the inspector out and inspect sand near it and I see our other diet that's location that station is out that's them that's the wrong layer so when they click next to it yeah you can see that it's located it's 371 meters but fifth bar two hundred rainfall stations that would be a bit of much work and there are far more efficient tools available in ArcGIS to do this in the spatial analyst tool there's an extraction tool spatial analysts extraction there's the extract values two points so we're going to use that tool but what you need to know is that this tool only works well when layers have the same coordinate system so when it's either and as and as our point data is in the British national grids and our elevation data is in wgs84 and the tool wouldn't work so we need Erie projects the elevation model to the British national grits or reproject s-- the rainfall stations to wgs84 and because and because it's the it's probably quicker to reproject the point data because it's a much smaller file so we're just going to do that and we can do that in data management and projections and then there's the project project tool and we select our impute data or rainfall stations and choose the different outputs put in the same folder she's the same filename just that wgs84 to the to the title and output coordinate system we just select geographic worlds WGS 1984 oh that's okay there we go and sure ArcGIS pick the best a coordinate transformation tool by default so let's click OK and it's running there we go we have a new set of points to its and and now they're in wgs84 so now we can use the the extract values two points from the spatial analyst tools and this tool go for each point look up a value from a roster so in this case for each point it will look look up elevation at that site so let's use that points extract values two points so extract selector points two turning points in wgs84 as input roster we'll choose our Scotland elevation model and as I put we'll call it this and was just at elevation to the name safe and optionally you could interpolate values between point locations so and you'll start interpolates values between grid cells now are a fictional all with is ninety meters is already reasonably accurate so don't think we need that let's just click OK that's running in the background it's done let's created this new file let's look at it as a good attribute table for this file so now we have we have our information we used to have and for a rainfall data for each month in an hour at the end there's a field called raster value and that's the value of the raster that extract values two points extracted and this contains the elevation of each station see we're pretty meaningful values for a life so that looks it looks about right to me sorry this is close that is attribute table and we can actually explore this data in few and then graphs create graph and we choose a scatter plot scatter plots and what we already have to rights they are Efron why we could put Seder rainfall in January and on the x-axis we do them put elevation which is storing rust or value and then we can see that whether or not there's a correlation between these two variables those other try striking correlation just seems a bit of to be it's a bit of an envelope at the base that seems to be the only relationship between the two and well if you click next you can enter titles and things to make our graph look more meaningful well every paragraph in in ArcGIS that's a quick way to make it to plot some variables in ArcGIS and explore your data

Channel: Yannick Kremer

Views: 8,887

Rating: 5 out of 5

Keywords: GIS, ArcGIS

Id: JKzK9VLX4Tk

Length: 5min 44sec (344 seconds)

Published: Sun Jan 27 2019