Garmin G2 HD Geraldton to Darwin Bluechart Micro/SD (010-C0869-20) Bluechart g2 HD marine maps allow you to see your vessel's precise, on-chart position in relation to navaids, coastal features, anchorages, waterways, obstructions, restricted areas and more with 1-foot HD contours for a more accurate depiction of bottom structure for improved fishing charts and navigation in swamps, canals, marinas and port plans.