Post on 20-Jan-2015
description
Aligning data
Sabata Mcatshulwa
Presentation Outline
Common problems
Coordinate Systems
Geoprocessing Tools
Presentation Outline
Common problems
Coordinate Systems
Geoprocessing Tools
Common Problems
Common Problems
Common Problems
Demonstration
Presentation Outline
Common problems
Coordinate Systems
Geoprocessing Tools
• A measurement of a location on the Earth’s surface
expressed in degrees of latitude and longitude
Geographic Coordinate Systems
Coordinate Systems
• Three-dimensional spherical surface to define locations on the earth
• If two datasets are not referenced to the same geographic coordinate system, you may need to perform a geographic (datum) transformation
• It is very important to correctly use a geographic transformation if it is required.
• A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. A GCS includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid).
• The spheroid defines the size and shape of the earth model, while the datum connects the spheroid to the earth's surface
Geographic Coordinate Systems
Coordinate Systems
• A method by which the curved surface of the earth is
portrayed on a flat surface
Projected Coordinate Systems
Coordinate Systems
Projected Coordinate Systems
Coordinate Systems
• Two-dimensional surface
• locations are identified by x,y coordinates on a grid, with the origin at the center of the grid
• Unlike a GCS, a PCS has constant lengths, angles, and areas across the two dimensions
• A PCS is always based on a GCS that is based on a sphere or spheroid.
• A frame of reference for measuring locations on the surface
of the Earth
• Cape (Port Elizabeth)
• Hartebeesthoek 1994 (Hartrao)
• WGS 1984 (Earth-centered = mass of the Earth)
Datums
Coordinate Systems
TM
• Two degree zones (Transverse Mercator)
• LO = TM x, Cape
• WG = TM x, Hartebeesthoek
Coordinate Systems
• South Africa or a different area
• Create a .prj file
• Update the parameters
Demonstration
Presentation Outline
Common problems
Coordinate Systems
Geoprocessing Tools
Geoprocessing Tools
• Vector
• Define Projection = To assign a coordinate system
• Project = Change a coordinate system
• Raster
• Raster Properties = To assign a coordinate system
• Project Raster = Change a coordinate system
Geoprocessing Tools
− Spatial adjustment • Projections - Shift data between coordinate systems• Transformations - Shift data in coordinate space
− Alignment tools• Bulk alignment
� Snap - snapping based on user specified rules� Integrate – will make feature coincident within a tolerance
• Interactive(New tools introduced at 10.1)� Align Edge - snap edges together to close gaps� Align to shape - adjust layers to traced shape� Replace geometry - create an entire new shape for a feature
Demonstration
Discussion