Raster Analysis in ArcGIS Pro: an Example

2023-03-22

Raster Functions in ArcGIS Pro

Raster functions are operations that apply processing directly to the pixels of imagery and raster datasets, as opposed to geoprocessing tools, which write out a new raster to disk.

Three types of functions are available in ArcGIS Pro:

Local Functions—A collection of ready-to-use raster analysis and management tools that are available in the Raster Functions pane.
Global Functions—Global functions provide you with the ability to perform processing at a specific resolution and extent.
Custom Functions—Custom functions can be written in Python and applied in the same way as out-of-the-box-functions.

Types of Raster Functions: examples

Local: Only use data in a single cell to calculate an output value
Neighborhood (Focal): Use data from a set of cells, also known as kernel
Global: Use all data from a raster layer

The powerful raster analysis toolbox

List of raster functions

Analysis
Appearance
Classification
Conversion
Distance
Hydrology
Math
Statistical
Surface
……

An example of raster function: (re)classification

Hydrology analysis in ArcGIS Pro

Drainage systems: The area upon which water falls and the network through which it travels to an outlet are referred to as a drainage system.

Digital Elevation Models (DEMs)

A DEM is a raster representation of a continuous surface, usually referencing the surface of the earth.

The accuracy of this data is determined primarily by the resolution.

Triangular Irregular Network (TIN)

TINs are a digital means to represent surface morphology. TINs are a form of vector-based digital geographic data constructed by triangulating a set of vertices (points). The vertices are connected with a series of edges to form a network of triangles.

TIN structure is a vector-based alternative to the traditional raster representation of terrain surface - Digital Elevation Model (DEM).

Unlike DEM, composed of regular grid, TIN facets have different sizes depending on data density. Because nodes can be placed irregularly over a surface, TINs can have a higher resolution in areas where a surface is highly variable and a lower resolution in areas that are less variable. You can include precisely located features on a surface—such as mountain peaks, roads, and streams—by using them as input features to the TIN nodes.

TIN can describe terrain surface better. However, TIN models are less widely available than raster surface models and tend to be more expensive to build and process. The cost of obtaining good source data can be high, and processing TINs tends to be less efficient than processing raster data because of the complex data structure.

Flow Direction function

An example

The Flow Direction raster function takes a surface as input and creates a raster of flow direction from each pixel to its steepest down-slope neighbor.

What is ModelBuilder?

ModelBuilder is a visual programming language for building geoprocessing workflows.

ModelBuilder in ArcGIS Pro allows you to do the following:

Build a model by adding and connecting data and tools.
Iteratively process every feature class, raster, file, or table in a workspace.
Visualize your workflow sequence as an easy-to-understand diagram.
Run a model step by step, up to a selected step, or run the entire model.
Make your model into a geoprocessing tool that can be shared or can be used in Python scripting and other models.

Elements of ModelBuilder

There are four main types of model elements:

Geoprocessing tools: perform various operations on geographic or tabular data.

Variables: hold a value or a reference to data. Two types of variables: data and value variables.
Connectors: connect data and values to tools.
Groups: are visual elements that group related tools together.

Elements of ModelBuilder

Data variables are model elements that store paths and other properties of data on disk. Common data variables include feature class, feature layer, raster dataset, and workspace.
Value variables are values such as strings, numbers, Boolean (true/false values), spatial references, linear units, or extents. Value variables contain anything but data stored on disk.

Make a Geoprocessing Model in ArcGIS Pro

An Example

This geoprocessing model is used by a conservation organization to identify potential habitats for an indigenous bird species based on vegetation type, distance from major roads, climate, slope, and elevation.

References

ModelBuilder

Raster functions

Hydrology toolset