GIS tools undoubtedly automate processes that used to take a long time to carry out. In general, manual tasks often require a great deal of effort to complete. Geoprocessing is the methodical execution of a sequence of operations over geographic data to create new information. The two fundamental purposes of these tools are to help with modeling and analysis, and to automate GIS tasks (ESRI, 2016b).
From this point onwards, the most frequently used tools will be those of ArcToolbox (), although some of the most common geoprocessing tools can still be accessed from the Geoprocessing menu. The use of each tool presents a similar structure: a pop-up window requests input and output files, apart from configurable fields depending on the nature of the tool.
8.1. GIS Book: Buffer
Imagine for a moment that a drop of water falls on a mass of water and generates a shock wave. The wave is shifted and the propagation phenomenon can cause positive or negative changes from its point of origin. Influence zones are polygons created from an entity at a set distance. This spatial analysis allows the affected surface to be identified (e. g. a new factory), influence zones (e. g. “opening of a road within a protected area”), those affected by a contaminant (e. g. “fertilizers”), and the range of antennas (e. g. telecommunications or weather radar). Using the Buffer tool, you can create influence zones for points, lines and polygons. The tool is available in the Geoprocessing menu bar or at the following address:
ArcToolbox > Analysis Tools > Proximity > Buffer
The “Buffer” pop-up window (Figure 31) can be configured in the following way:
- Input Features: Select the layer of points, lines or polygons.
- Output Features Class: Select the directory or geodatabase where the resulting entity will be stored.
- Distance [value or field]: There are two options: “Linear unit”, which allows you to set a fixed value with the respective unit (e. g. meters), and “Field”, which creates an influence zone based on the values of a field selected from the attribute table.
- Method: Specifies the method used to create the zone of influence. The “Planar” method uses Euclidean distance (as if measured with a ruler in a projected plane), and “Geodesic” takes into account the curvature of the earth regardless of the layer coordinate system. Influence zones are not influenced by the distortion of a projected coordinate system.
Figure 32 shows influence zones for three points, one line and two polygons using a linear unit of 20 meters and the planar method as a distance.
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