Once
you have taken all images and safely stored them on a
computer, you may use them independently or merge them using
appropriate software.
Merging techniques are generally well
described in the manuals accompanying the software provided
together with professional digital cameras.
The saved image(s) are now in
raster image format ready for digital
extraction, correction and geo-referencing. This requires
their conversion to vector format through onscreen
digitizing. This requires their conversion to vector
format through onscreen digitizing.
Onscreen
digitizing, as opposed to tablet
digitizing, is increasingly becoming the most popular
means of creating GIS spatially organized data.
On-screen
digitizing captures data from digital images or scanned maps
by using the mouse instead of the cursor. This allows for
creating map layers by adding labels during tracing. While
the features are still manually traced, and provided images
have been taken at high resolution, on-screen digitizing
grants a higher level of accuracy because the operator can
use the zoom facility. In addition,
on-screen digitizing allows for editing features when enough
information is available from the image.
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A raster image file is
generally defined as a rectangular array of regularly sampled values, known as
pixels. Each pixel (picture element) has one or more numbers associated with it,
generally specifying a color, which the pixel should be displayed in.
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A vector image is generated
through a sequence of commands or mathematical statements that place lines and
shapes in a given two-dimensional or three-dimensional space.
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