model builder

I did not realize how easy to use ArcGIS and IDRISI before i found modelBuilder. The simple way to explain ModelBuilder is it works as the way your brain works. It put everything in graphical model, and by simply click “run” button, you will see that this is not just an ordinary box as in visio or in chart in your M.Word. It really runs !! it runs the process using the input, and producing the output which again is used by other process, and so on so forth untill the end result coming. Amazing.

I would say model builder from IDRISI, ArcGIS, and ArcView principly the are just the same. the different is only on how we use it. In this post, i will focusing my discussion on using modelBuilder in ArcGIS.

in ArcGIS, you have installed modelBuilder, unlike in ArcView where you have to install spatial analyst, the only thing you should do is just make sure that your spatial analyst extention is checked. Then you ready to go.

modelbuilder

first, open your ArcToolbox. there you will find a whole bunch of tools use in ArcGIS inclusing famous RUSLE model to explore the soil erosion untill KRIGING methods for geostatistic. Everything is there!.

Btw, i forgot to tell you, why we should use model builder? why not we just use ordinary functions? The answer is modelBuilder offers a lot more easier process and each time you want to change something/parameters in one or all your process, you can easily done it simply by correcting it in one of your box. The modelBuilder is like the living flow chart!!.

ok, now after you open your ArcToolbox, right click and choose new toolbox. Then they will ask you to set parameters. Ignore this for a while, let us take the given value and continue to the main board of model builder.

Built-Up Density

Built-up density is important for planners like us. I remember when I made my final project titled Urban Fire Risk in Bandung. In my final project, one of the criteria to derive the risk index was by employing “population density”. The main problem is that this data were come in regional based, which mean it does not contigious and not so reliable. Population density every where in Indonesia is based on Kelurahan (village administrative unit). Density is caunted firstly by summing the population per village and divided with the total area of the the correspond village.

I read many article try to solve this problem by applying other demography instrument, one of it is by using built-up density. Built-up density is based on a though that population living in area must have a linier correlation with the place where he/she lives. In other words, buil-up density must have reflects the population density. The higher the population density, the more higher built-up density, or vice versa.

then, our question is, how to make the built-up density? simple. First think that you should have are;

1. installed ArcView and ArcGIS 8/9 with Spatial Analyst extention checked in your computer
2. Land use data in vector based
3. I use Xtools, additional tools for ArcView 3.3

How to make it? I will explain you the logic thinking behind all these functions before we go step-by-step through the functions. OK, the key is we will make the built-up density by using “density” function from spatial analyst ArcGIS. this function requires you to have vector point input WITH the value attached on to it. Suppose, the value of the point is the size (in hectare) of your built-up area.

then, the next question is, how to make vector point? Simple. first you have to view your land use vector layer. then, select all your built-up area including for example, stadium, school, commercial, and industrial. Use select wizard from ArcGIS/View to make your live easier. Make your selection into new layer and named it “built-up”. After you are sure you have separated the built-up area from other land uses, then now calculate the area of your built-up area polygons by using “calculate perimeter, area” from XTools ArcView.

Next step, open your ArcView and display your built-up layer. Then convert this polygon into vector point by using XTools “convert shapes into point”. Voila!!, now you already have an input for “density” functions. Go through density function in ArcGIS and choose your optimum searching area.

Any question can be posted in comment coulomn.

Thnx