Method and system for compression and reconstruction of cultural data for use in a digital moving map display

For use with an information display system, an arrrangement for compressing data from which a linear feature is to be produced on said display comprising:

• first means for storing the address of an initial point at one end of said linear feature;
• second means for storing a code representative of the direction in which said linear feature extends at said initial point at one end thereof;
• and
• third means for storing a plurality of delta code values for identifying a further point and successive points on said linear feature in terms of their relationship with the direction of said linear feature as originally identified by the initial direction code as stored by said second means and the direction for each successive one of the individual points thereon, said delta code values being selected from an elongated footprint pattern of points which is oriented so as to extend at each of said successive points on said linear feature away from that point in the direction of said linear feature at that point, said elongated footprint pattern including a major lobe corresponding to a single quadrant and a contiguous minor lobe at a corner of said quadrant, the footprint pattern being oriented so that delta code values may be selected at each of said successive points so that said initial point on the linear feature falls within said minor lobe and said major lobe extends away from said point in the direction of the linear feature to that point.