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## How do you make Thiessen polygons?

Thiessen proximal polygons are constructed as follows:

1. All points are triangulated into a triangulated irregular network (TIN) that meets the Delaunay criterion.
2. The perpendicular bisectors for each triangle edge are generated, forming the edges of the Thiessen polygons.

How do you estimate the mean rainfall using Thiessen method?

3) Thiessen Polygon – This is another graphical technique which calculates station weights based on the relative areas of each measurement station in the Thiessen polygon network. The individual weights are multiplied by the station observation and the values are summed to obtain the areal average precipitation.

How do you make Thiessen polygons in Arcgis?

The instructions provided describe how to create Thiessen polygons for line features.

1. In ArcMap, run the Feature Vertices To Points tool.
2. In the Feature Vertices To Points dialog box, select the Input Features and the desired Point Type, and click OK.

### What is the difference between the voronoi and Thiessen polygons?

Yes, they are the same thing. In the field of GIS we tend to refer to them as Thiessen polygons, after the American meteorologist who frequented their use. In other fields, particularly mathematics and computer science, they are generally referred to as Voronoi diagrams, in honour of the mathematician Georgy Voronyi.

How Thiessen polygon method is different from Isohyetal method?

The Thiessen polygon method obtains the average precipitation by weighting the area of each station. However, the isohyetal method applies the area weight to the average rainfall between isohyets rather than directly weighting the observed rainfall.

Why Isohyetal method is better than Thiessen polygon method?

Answer: The isohyetal method is considered to be more accurate than the Thiessen polygon method or gridpoint technique to estimate rainfall totals because it includes the effects of local features.

## What do you call a graph plotted for discharge vs time?

A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow is typically expressed in cubic meters or cubic feet per second (cms or cfs).