Introduction:
Nearest Neighbour Analysis (NNA) is a technique of determining the spatial distribution of point based objects on map. It is a well known Applied Geographic Technique used for measuring "spatial distribution and interaction of geographic phenomena on the geographic space."
Most popular use of this technique is identifying the rural settlement types.
Proponents:
That technique is known as Nearest Neighbour Index (NNI) which was originally put forwarded by two biologists Clark and Evans and in geography it was introduced by King and Dacy.
Assumptions:
1. Distribution of points on the geographical space is random.
2. The probability distribution of the distances between the points and their nearest neighbours as normal.
Equation and Significance test:
Step-1: Identification of the settlement patches on the given map area and trace the settlement patches.
Step-5: Calculation of the mean expected distance from the given formula.
Step-6: Calculation of the Nearest Neighbour Index (NNI) using the formula.
Step-7: Interpretation of the value with the help of the scale given by the proponents.
Step-8: Test of significance of the index value.
Disadvantages:
The method is simple to understand but it has some major drawbacks.
1. The boundary demarcation is subjective. Any changes in the boundary may influence the index value.
2. It does not distinguish between single and multi clustered pattern.
3. It actually averages out the sub patterns observed within the area.
Points to be noted:
No point outside the boundary of the given area is generally included in the study.
But if the nearest neighbour of any point lies just outside the boundary the distance should be counted.
See Video
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