GIS2: Geo-processing and Metadata Treg Christopher

Three Views of a GIS The Map View The Database View The Model View

Three Views of a GIS The Model View : –A GIS is a set of information transformation tools (i.e. geoprocessing) that derive new data from existing data.

What are the three types of vector data? Geoprocessing using Vector Data Points, Lines, Polygons

Vector Data – Overlay Analysis Union –Spatial features and their attributes are joined to create a new layer

Vector Data – Overlay Analysis Intersect –Only the features that are common to both layers are combined to create a new layer Identity

Vector Data – Overlay Analysis Erase –Remove an areas from the larger, geographic area –Example: Where are endangered nesting areas where human activities aren’t allowed?

Proximity Analysis :Nearest Neighbor

Vector Data – Proximity Analysis Buffer: –find features contained inside or that fall outside the specified distance. –Points, lines, or polygons –Different buffer distances –Multiple bands –Overlapped or dissolved zones

Proximity Analysis :Variable Width Buffering Width of buffer varies by attribute value Example: a buffer based on stream type and Timber BMP Ephemeral - small or no buffer Intermittent- 30ft Perrenial-150ft

Vector Data – Feature Extraction Clip –Includes only those features of the input theme that are within the areal extent of the clip theme. –Isolate a particular area of interest. –For aesthetics, storage space and processing time –Input layer be point, line, or polygon features, but the clippinglayer (i.e., "cookie cutter") must be a polygon layer.

Dissolve –Removes boundaries between polygons that have the same value of a selected attribute. –Reduces processing time, visual clutter, storage space Append –Add tiles together to create one layer –Large datasets are often tiled Soils (by County) Topos (by 7.5minute Quad) Other geoprocesses

Geo-processing use Raster Data Square cells of equal size Raster (grid) is well suited for computing because: (1) grid cell have fixed locations, and (2) grid can be treated as a two-dimensional array; Number of columns Cell size Examples?DEM, Satellite Imagery, Aerial Photo

Raster Data Analysis Map Algebra Local Operation Single grid

Raster Data Analysis Map Algebra Zonal Operation

Zonal Mean Example - Map Algebra Zone Grid Target Grid Result

Three Views of a GIS The Database View : –A GIS is a unique kind of database of the world—a geographic database (geodatabase). It is an "Information System” for Geography. Spatial Data Attribute Data Metadata

What is Metadata? 1. What does the data describe? –What is geographic area of the data? –When was it collected? –what are the units of measure? 2. How reliable is the info? –How was the data generated, processed, and modified? 3. Who produced the data? What is the data type? 4. What is the projection? 5. What does each value in each field of the table mean? 6. How can I get it? Usage restrictions? 7. Who wrote the metadata? Example of Metadata at:

Steps in GIS for Your Project Identifying the goals of the project Identifying the questions Choose the data Choose the tools to analyze the data Conduct the analysis and generate results

Example: Finding sites for creating new campground areas The goal –Find public places in Chittenden County that are suitable for low-level development as campgrounds. The questions –What are environmental concerns for this development? Water quality Damage to vegetation –What makes a campground suitable to the user? Microclimate Proximity The data –Environmental concerns Hydrology (streams, lakes), Wetlands, Areas of threatened species –Human concerns Slope, Aspect, Roads, Trails

The Tools Confine to Project Areas (Clip) Proximity to Features (Buffer) Remove Buffered Areas (Erase) Find areas of low slopes (Intersect)

ArcIMS Viewer for Chittenden Website at:

End Questions?

Review Questions Geo-processing is a part of which of the 3 views of a GIS? List and describe 4 types of overlay analyses Be able to describe real life examples in which you would use these Describe “buffering” and give an example of it’s use Describe “clipping” and give an example of it’s use Be able to distinguish between examples of zonal, raster processing and cell-by-cell, raster processing What is metadata? List and describe 4 of 7 elements of metadata