RUBBER SHEETING & EDGE MATCHING
What is Rubber Sheeting?
Definition: Rubber Sheeting is a process of
spatial transformation that allows a distorted layer to be seamlessly attached
to the adjacent geographic layer of a matched image. In another way it’s
defined, Rubber sheeting is a process in which the size and geographical location
of an object can be transforming in a non-uniform manner. Most of the time
rubber sheeting helps in converting unknown coordinates in GIS data sets to
known coordinate systems.
Why
using Rubber Sheeting?
The two data sets do
not match geometrically. One of the data sets is unknown.Geometric distortions
usually occur in source data. Imperfect registration in map composition, lack
of geodetic control in data and others causes are involved in geometric
distortions in the source data. In this situation rubber sheeting is required to
make small geometric adjustments in source data.
HOW Rubber Sheeting works?
Rubber Sheeting process
is done in some simple steps-i) identify related points in the two data
sets. ii) Connecting the corresponding points by a vector. iii) Drag and drop
the lesser known data set points until all vectors have been reduced to zero.
Two temporary TIN-like
structures have been created for the source and target data layers using
triangles in Thiessen Polygons / Delaunay constructed from the control point.
Each corner of the triangle has X, Y, Z coordinate. Here triangle corner
assigned as a node. Each node has XY locations and Z value. Where the Z value
represents the amount of adjustment between the end of a link (source) and the
end (target). Two interpolation methods
used in the rubber sheeting adjustment one is linear and another is natural
neighbor.
Software
uses:-
ArcGIS 8.3,
ArcMap9.2,QGIS, AutoCAD Map 3D, etc.
EDGE
MATCHING
WHAT IS EDGE MATCHING?
Definition: Edge
matching is a spatial editing method that ensures that all features across the
sheets of the adjacent map are on the same edge locations.
Significant
characteristics: -
i) The Edge Match tool
lets you create displacement links that connect the ends of two adjacent layers.
ii) The less accurate feature layer is
adjusted, while the adjacent layer is used as the control.
Example: In the GIS
database, when you have two
counties with disconnected lines at the borders of digital map, you should use
the edge matching tools to connect them. In this operation Links are used when
matching features in adjacent coverages.
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