Frequently Asked Questions -
How to Georeference A Bitmap?
Collection by Stefan A. Voser |
MapRef
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8. October 1998 |
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Table of Content
Bitmaps and Raster
data
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There exist different types of two-dimensional raster data with different
semantics:
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raster element represents a point: vertex (e.g. for digital terrain
models)
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raster element represents an area: pixel (e.g. raster images, graphics,
scanned documents, bitmaps)
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In the most cases, raster elements are aligned in rows and columns
with equal spacing in rows and columns
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raster data are referenced to a raster coordinate system (coordinates
are described by number of row and column, as integer or real numbers (for
measuring subpixels)
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the origin of raster coordinate systems vary:
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vertex coordinate systems: first element for row and column: 0 or
1
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pixel coordinate systems: origin at the border or in the centre
of the pixel, => offset of 0.5 pixel
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raster coordinates have no units
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metrics of raster coordinates are derived by defining the spacing distance
for rows and columns:
Georeferencing a Bitmap
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© by Stefan A. Voser
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