Question 2

Part A

Line Vector File Overlayed onto Rasterized Line Data

line.vec file here

Part B

The line.vec ASCII file holds data in a similar manner as other vector data, with feature ID's, number of values and x, y co-ords, but since the data stored is to represent a line, the feature ID has more values attached to it, eight in the above example; so we know that this is a line with eight values.  The file is documented so as to port to Idrisi with "values".

After the file is converted to a binary type, a LINERAS function is executed, following an INITIAL function to create the backdrop raster image.   The image file is updated with vector line attribute values in overlapping areas of line.img.  For example, we know that the first value of the line is 0.5 3.5.  When executing LINERAS, this value is picked up within the corresponding values of line.img and the cell value is changed to record the line data.  This occurs throughout the entire line and ends at 0 0, where the line.vec file states.

In analyzing this file, a pattern evolves where values in line.vec are absolute.  For whole x values, the proceeding pixel is shown when rasterized (e.g. feature 2, 3, 4, 5), whereas the preceding pixel is shown for y values (e.g. feature 2, 3, 4).  One also sees that features 8 and 9 are not generated on the rasterized image, because of the y value assumption made earlier for line.vec.  For feature 1, since the co-ordinates are not whole values, the pixel in which that feature wholly resides is displayed.

Since the line has one feature ID, the colour of it when displayed is constant.

 

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