Definition:What is data?Data is anything in the form of1. Charts2. Tables3. Text4. Maps5. Photos6. Imageries, etc.

Examples of data

Data vs. Information• Data are collection of facts• Data are observed/recorded• It simply exists and does not have meaning

of itself• Information is obtained when the data is

summarized/analyzed and the result is put into a meaningful context

Data vs. Information

Data Information

Beyond Data & Information

DataInformation

Knowledge

Wisdom

Sources of GIS data1. Existing Maps (analog & digital)2. Remotely sensed data

a. Photographsb. Satellite Imageryc. Lidar

3. Field observationa. Survey / Samplingb. GPS data

Most of the GIS data are now available online from respective State GIS data

clearing house

www.granit.sr.unh.edu In NH (GRANIT):

In VA (VGIS): www.vcgi.orgIn MA (MASS GIS): www.mass.gov/mgis/

www.gis.ny.govIn NY:

Sources of digital data

Sources of digital data

Data formatMost of the vector GIS data are in• Shapefile (ArcView 3.x)• ArcInfo interchange file (.e00)

You have to use Import function in ArcGISto make an ArcInfo interchange file usable!

Data format• We will be using Geodatabase in

this class• Shapefiles can be exported to a

feature class in a Geodatabase

Advantage of Geodatabase

You can easily get the total length of Roads in NY!

Feature class provides updated length of line feature

Advantage of GeodatabaseFeature class provides updated area & perimeter of each polygon in a Geodatabase

What about area in a shape file?• Shape file does not update the area of a

polygon in the output layer• You have to manually update it!