an overview of geoprocessing

GeoprocessingGeoprocessing is a fancy name for Spatial Operations

So what is Geoprocessing?Processing or manipulating of geographic/spatial data to create a new dataset.

Example of a simple process

Water

Sugar

Flour

MIXED DOUGH

A typical GeoprocessingInput

DatasetOutputDataset

Geoprocessing

UnprojectedData Project

ProjectedData

• A process contains tool• And a tool has parameters

Input Data Output DataTool

Geoprocessing/Model building

ProcessProcess

Process

Tools in ArcToolbox• There are literally hundreds of Geoprocessing tools available in ArcGIS!

• Most of the time you will use only a few of them

Geoprocessing MenuCommonly used tools are available from Geoprocessing menu!

Environment Settings

Application level settings affect all tools and menus Tool settings affect one execution

of one tool

Workspace settings

• Current and scratch workspace

• Output coordinate systems

ArcToolbox has many tools

Map Overlay• Map overlay brings data from multiple

layers into one• There are two basic categories of map

overlay functions1. Functions that combine attribute data

&2. Functions that do not

Overlay operations in ArcGIS

1. Erase2. Clip3. Union4. Intersect

Overlay operations combine more than one layers into one.Some of the extraction function can also be considered as overlay function

Extraction only & does not combine attribute from layers

Combine attributes from layers

Select by locationCan’t truncate the roads at the boundary!

Clip is the rescue!Clip is used to cookie cut the original ROAD layer into a smaller layer

What is Clip?Clip is used to cookie cut the desired areas

EraseOnly the features outside the Erase feature are kept, everything else are erased

DissolveDissolve is used to aggregate features based on specified attributes

If you don’t choose an attribute, it will dissolve all into one!

How to simplify the landuse data

DISSOLVE

Dissolve wizard

What is Union?Union combines two polygon layers together

What is Intersect?Computes geometric intersection of two layers

Example of intersectAreas common between the two layers.

INTERSECT

3500’ buffer 2000’ road buffer

Buffering Lines

250’Buffer

Using attribute table in buffering

Variable buffering using attribute

Multiple Ring Buffer

Multiple Ring Buffer

Buffer around Toxic Sites & water well location