Environmental GIS Nicholas A. Procopio, Ph.D, GISP

What’s in a name? Not all Arcs are the same!

Question? What is the landscape make up of each of the watersheds? What is the best way to evaluate this? What spatial tools will accommodate this analysis? Intersect and Union

Land-use/Land-cover data

…and watersheds of interest.

Spatial Analyses Intersect Computes a geometric intersection of the input features. Features or portions of features which overlap in all layers and/or feature classes will be written to the output feature class. Union Computes a geometric intersection of the Input Features. All features will be written to the Output Feature Class with the attributes from the Input Features, which it overlaps.

So which to use?

The layout, again.

The Inputs The (Intersect) Inputs

The (Intersect) Output

The (Intersect) Output Table

The (Union) Inputs

The (Union) Output

The Union Overlay

The (Union) Output Table No Overlap

Select data can easily be exported into spreadsheet for easy summary analyses. Did you recalculate area? This is extremely important.

Land-use data summarized by watershed

The pitfall! Slivers

Other Useful tools What other tools do I use frequently? Clip - Extracts input features that overlay the clip features.

Other Useful tools What other tools do I use frequently? Select by location - Select target features that overlay source features.

Other Useful tools What other tools do I use frequently? Buffer (Multiple Ring) - Creates multiple buffers at specified distances around the input features. These buffers can optionally be merged and dissolved using the buffer distance values to create non-overlapping buffers.

Other Useful tools What other tools do I use frequently? Merge - Combines multiple input datasets of the same data type into a single, new output dataset. This tool can combine point, line, or polygon feature classes or tables. Use the Append tool to combine input datasets with an existing dataset.Append

Other Useful tools What other tools do I use frequently? Point Distance - C omputes the point-to-point distance between each point in a feature class or layer to all points in the same or different feature class or layer, within a specified search radius.

Other Useful tools What other tools do I use frequently? Dissolve - Aggregates features based on specified attributes.

Other Useful tools What other tools do I use frequently? Spatial Join - Transfers the attributes from one feature class to another feature class, based on the spatial relationships between the features in the two feature classes. Usage This tool is used to transfer attribute fields between feature classes. The attributes from the Join Features are added to the Target Features whenever a specified spatial relationship (or Match Option) is found. For example, if a point feature class is specified for the Target Features, and a polygon feature class is specified for the Join Features, with a Match Option of WITHIN, each output point feature will have, in addition to its own original attributes, the attributes of the polygon that it is within.

ArcGIS Extensions

Add-ins Xtools - Geospatial Modelling Environment and Hawths Tools Export to KML Also check out for many, many, more add-in extensions.

You will find your favorite!