Projection - The two-dimensional representation of the three-dimensional space.
Coordinate System - a reference system for measurements defined by the projection
Geographic Coordinate System - measures locations in degrees - latitude and longitude. Since latitude and
longitude are angular measurements they are not suitable for measuring distances. The
major parameter of a Geographic Coordinate System is its datum
Projected Coordinate System - uses a projection to transform the latitude and longitude
to X and Y coordinates and makes the linear measurements more accurate. Each projected
coordinate system is based on a Geographic Coordinate System
Spatial Domain - the range and precision of coordinates that can be stored in a
Spatial Reference - contains information for the coordinate system and spatial domain
extent for a feature dataset
Projections of the data
Projected data - the data is explicitly projected in a Projected Coordinate System
Unprojected data - the data is in a Geographic Coordinate System
Data with unknown projection - the projection information is missing
ET GeoWizards works with data in any projection.
All the wizards preserve the Spatial Reference of the input data source
unless an option is available and the user selects it. The assumption
is that if the user keeps a dataset in certain projection he has reasons for that,
and all the products of this data set must be in the same projection.
When a distance input is required ( Fuzzy tolerance, Dangling tolerance etc. )
best results will be achieved if the data is projected in a specific projection, because the
tolerance is compared directly with the data.
Although possible, it is not recommended to manipulate Unprojected data (data in a Geographic Coordinate System) for reasons