# Concept of Cost Distance Analysis and Two Types of Cost Distance Operations (Especially for GATE-Geospatial 2022)

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The Cost Distance operation creates either a physical distance dataset or cost distance dataset, and optionally two different types of allocation datasets and direction datasets could be created.

If a raster dataset is specified as the cost dataset, the cost distance dataset will be created with the corresponding allocation and direction datasets to be created optionally; otherwise, the physical distance dataset and the optional allocation and direction datasets will be created.

## Source

The interested objects, e. g. school, road, or stream.

## Source Dataset

The point, line or region dataset which contains the source.

## Distance

Distances in raster data analysis could be expressed as physical distance or cost distance. The physical distance, also called Euclidean distance, measures the distance between the center of the source cell to the center of each cell. The cost distance measures the cost for traversing the physical distance. A cost distance measure operation uses the cost or impedance to move through each cell as distance unit.

## Distance Dataset

The raster dataset for the physical distance or for the cost distance. Each cell value in the dataset for the physical distance is the physical distance from the center of the cell to the center of the nearest source cell, while each cell value in the dataset for the cost distance is the cost distance from the center of the cell to the center of the nearest source cell. ′

## Allocation Dataset

Each cell value in the allocation dataset is the value of the nearest source cell. For each cell, the nearest source cell in the physical distance measure operation is determined by their physical distance, while determined by their cost distance in the cost distance measure operation.

## Direction Dataset

In the physical direction dataset, each cell value is the direction from the cell to the nearest source cell, which is measured by calculating the angle away from the north clockwise. The direction is measured in degrees.

In the cost direction dataset, each cell value measures the direction from this cell to its adjacent cell along the path to the nearest source cell, which could be one of the eight principal directions.

Given figure, based on the source cells denoted as 1 and 2, (a) shows the physical distance measures in cell units from each cell to the closest source cell; (b) shows the allocation of each cell to the closest source cell; and (c) shows the direction in degrees from each cell to the closest source cell. The cell in a dark shade (row 3, column 3) has the same distance to both source cells. Therefore, the cell can be allocated to either source cell. The direction of is to the source cell 1.