Suitability: Working with Booleans in Rasters & Vectors

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Suitability Analysis In Arc GIS Pro...

As a GIS Analyst, we may be called to action in some pretty epic ways. For today's blog post, we are going to talk about how a GIS analyst can assist a property or land developer in visually and statically seeing how much land they can develop on before actually beginning construction .This is a crucial role as a GIS Analyst, simply due to the sheer cost of money and time that goes into land development. 

More importantly, we are doing Suitability Analysis...


We need to find what land is "Suitable" for development!

  1. "the quality of being right or appropriate for a particular person, purpose, or situation." -   Oxford Languages by Google

Most developers want to see what suitable locations they can build on and estimate the total amount of land available to them. The benefits of seeing these results before actually starting the land clearing and construction phases is that the property developers can what room they have to build. they can see if certain building projects are suitable for construction in this area or not before investing million of dollars on people and equipment. 

In this scenario, we are going to look at some environmental factors of the land area that the property developer is going to want to make this land suitable for development. Things to consider are the following...

  • Elevation - Primarily slope derived from the DEM
  • Land Cover
  • Soil
  • Streams in the area
  • Roads in the area


The First thing we need to do is establish the Land Cover for our property area. We can take the Landcover Raster and use a tool called Reclassify Raster to redefine the parameters for this particular raster file. We can set the Boolean values in our raster ( numbered values) to each cell in the image. Each cell represents some type of land, whether its forest, march, or river. So we code the pixels with numbered values to represent these land types. For this project, we are going to set the parameters for agricultural land, forest, meadow, barren, shrub, Urban and wetlands. We will give these land values in our new raster a suitability rating from 1 to 5, 5 being the best. We want land like agricultural to be a 5 because it is good land to develop on. Urban land however we will classify as a 1 because it is already developed and not a great choice for this project. 

https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/reclassify.htm

https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/euclidean-distance.htm

Landcover

Check out the Landcover below:


Now look at the reclassified Raster of Landcover after we run our tool:



Now we are going to reclassify some of the other rasters we established earlier in the project...

Slope


slope (From elevation) - We actually need to run the Slope Analysis Tool first using the elevation raster (DEM) as our input raster. 

Slope

Slope Reclass: Run the Reclassify Tool again on the Slope Raster above and set the parameters in which we code a low slope as a high sustainability rating. so 0 to 2.0 is a 5, 2.0 to 5.0 is a 4, etc... 

A property developer or builder wants a low slope because that is not difficult to make level and costs less  money to conduct construction.  

Soil


Next is The Soil Raster: 
Soil Raster: We had to convert our soil Shapefile because it was a Vector File and not a raster. We ran the Polygons To Raster Tool to convert the soil to a raster file. 

Soil Reclassified raster: We selected the Boolean Suitability values of 0 rated at 5, 4 rates at 3, 5 rated at 2, and 6 rated at 1. This means we want soil class 0 as much as possible (it gets a 5 rating)


Distance To Rivers

We need to run the Euclidian Distance Tool to get the distance to the rivers. 

Now we will reclassify the image using a reclassify raster tool. The cell values will be 0 to 1,000 feet to a 1 rating, and anything over 1,000 feet to a 5 rating. We don't want to develop land on a river, so we want the 5 rating of land that is over 1,000 feet away from rivers. 



Distance To Roads

We will do the same thing for our roads. We will use the Euclidian Distance Tool and run the roads. We will then reclassify the roads to a 1 through 5 rating scale, trying to get the roads from a 0 to 1,320 feet distance. We want to build within 1,320 feet from roads due to transportation, utilities, and easy access for development. 


 Weighted Overlay Tool

https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/how-weighted-overlay-works.htm


We will set the 5 rasters to an equal weight of 20% to calculate what areas affect our final output. 

Then we will run the Weighted Overlay Tool again with some different weights on our rasters,...


▪ Land cover – 20%
▪ Soils – 20%
▪ Slope – 40%
▪ Distance to Streams – 10%
▪ Distance to Roads – 10%

Look at the results below. On the left is all 5 rasters with equal weights. The one on the right is all 5 rasters with slope having more weight and the distance to the rivers and roads with less weight. 

Which one do you think is the better method? 

As a GIS analyst, we determine what weights we want to use when calculating Suitability ratings. We do this when we reclassify the raster we are using, and when we overlay them on top of each other with weighted percentages. We determine what should affect our output the most. In this scenario, slope has a major affect on construction. This is due to costs, transportation, labor on leveling land, so we want that to have the highest weight. In each scenario or project, it is up to the analyst to determine what weights should be applied to the defined suitability rating scale. 


In this case, I would say the area to the right is better or more accurate due to changing the weights to make slope a greater weighted value when completing our final raster. The 5 value is what we are shooting for. We have 1.22 km squared of suitable development land. The map on the left is showing more land than on the right. This is because slope ahs a greater affect on the right changing the final output. 

Boolean Raster Models

When doing Boolean raster / Vector Analysis you can build a model in Arc GIS Pro to automate reclassifying your rasters and overlaying them together for a final output. Below is an example for future Suitability projects. 


Check out this video on Suitability with rasters 
in Arc GIS Pro




I hope you liked this very long post!


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