Part A
poly.vec file here
The poly.vec file shows us data about a vector polygon. It's attributes are similar to that of line.vec, but the final value of every polygon feature is equal to the first value recorded, hence a polygon. As with all .vec files, the file ends with 0 0 after the last record to signify the end-of-file.
The Document module in Idrisi again 'ports' the file so as to work with the software. The file is converted to a binary filetype to work with the values.
The POLYRAS function itself correlates the polygon values to those of poly.img, and highlights cell values which 'match' or line up. The image at this point is quite 'blocky' as highlighted cell values within poly.img are shown, which does not show the true attributes of the file. POLYRAS then highlights all cells within the data so as to create a rasterized polygon. It is understood that all pixels encapsulated within the polygon borders have a given value, hence a polygon display. From the above image, it is evident that the method used to assess pixels values here is that of "predominance" where the majority of the pattern in the pixel takes that value. Some form of data error is also evident here (stair-step), between the second and third value of the polygon. Therefore, data error increases with pixel size.
It is when adding poly.vec as a layer to an existing image that we see the polygon data truly 'rasterized'.