Well there are two which is called mosaic. So here is ArcMap workspace and I just downloaded a world dm 15 arc second resolution for sale size is 450 meters. Let's have a quick look of the data. The data is by pieces. Africa, Asia, Europe, Australia, syndrome America, North America and South America. seven pieces of city from the hydro state.
It's basically our Shuttle Radar Topography Mission product and they'd has different resolution Like 30 arcsecond resolution which means each pixel each cell size is 900 a meter sometimes is quoted as one kilometer 15 arcsecond each cell size is a 450 meter, 90 meter dm, which is the three arcsecond resolution and this 30 meter dm, one arcsecond dm. With finer resolution, there will be more columns and our eyes and that will be a big amount of data from a raster file. My computer memory wouldn't be able to handle that. So, for this demonstration, I will just use 15 arcsecond. The cell size is approximate It must be 450 meter. When I say cell size, I mean that's I mean Chengdu right now.
Okay so this is a one sale as measured site 400 meters This is 450 meter. It's open arctoolbox data management tools, raster raster data set mosaic. There are actually two tools can do this one is called Mosaic, once called mosaic to new raster the mosaic it will merge multiple existing raster into a existing raster data set. mosaic to new will merge them When people raster data set into a new raster data set, I will use this one because I don't want to change my existing data I want to create a new one. So mosaic to new raster input rasters has all my seven. Well, I can click click each one and use this tool here to do this practice.
But since we have already have our new friend, model Buder, and Python with ArcGIS, let's just to go here. Just add on one or two Monty find this Python script a little bit itself to well put up all the input data Oh my seven d m data set as the input, I will write a loop quickly here. Okay, so I did a little bit of modification here. I import the OSS well because I want to use the OS dot Lister directory to reading all the rasters into a list. I need the T file and I keep everything else the same as the way it was exported from moto beauty. Here I changed that this variable a little Then I tested earlier with eight bit, almost find the value range only goes to 255.
But the highest elevation is over 8000. We need a bigger volume on the data. Again, that's your one. It wasn't working because I put the wrong directory. That's right. get you to work that's at the data.
Give it time to die he or she puts a change in dm layer transparency very 10% is better. Now it looks better. Let's learn how to extract. From here. We will extract a DM for only the United States. Let's add to the boundary first.
This is the United States. export the boundary will only you as first. So, click the black feature to select a boundary for United States and click on layer data export data export selected features extracted by map the input raster feature mask export output, which is the boundary for United States and is the final result about the mosaic and extraction being class two, we learn the flow direction and flow accumulation from FDM and today I'm gonna introduce a new tool which is called basic bass into will create a raster delineating our drainage obey things. The input is flow direction raster. Okay, let's gain the pythons Script first. Okay, so the syntax is are the pi.tp dot basing, underscore input and output.
We are actually used Python script or class to add this at the end. Let me change this code quickly Okay, so here I changed the environmental workplace. I changed the flow director, I changed the file, I changed the input, directory and the name and the for all the FDM MTR FA CC. And the best thing I get me to correct directory and name and all the process I just for the process, I deleted a one which will create a stream and I added the GP dog facing function, the flow direction here and then the out is just called basic. I will put it here. That's the one.
This is the final result with all the bases in the world. Next time I will introduce another way to create Facing Watership