Map Description and Management by Spatial Metadata: Requirements for Digital Map Legend for Planetary Geological and Geomorphological Mapping

Instruments carried along on missions to, e.g., Mars, the Moon, Venus, and various Outer-Solar System objects, produce a rich variety of image data recorded in different wavelengths and some of them allow to derive additional datasets (e.g., digital terrain models). These data form the basis for geologically exploring the evolution of planetary bodies by analyzing and geoscientifically interpreting surface structures. By using modern GIS techniques the results are represented in thematic, mostly geological and geomorphological maps and allow to extract additional information, e.g. by means of morphometric measurements. To allow for an efficient collaboration among various scientists and groups, all mapping results have to be uniformly prepared, described, managed and archived. In order to achieve this, GIS-based mapping approaches are currently underway. One of the important aspects in this context is a detailed map description and an efficient management of mapping results by using metadata information. Such data describe, e.g. the geometry, extent, quality, contents and conditions of source data and additionally allow detailed queries for context information. We are currently working on the evaluation and creation of metadata templates that deal with individually descriptive elements of planetary mapping results. Such templates then form an obligatory component to be filled in by the user/mapper after mapping conduct. The first step on the way to such a generic data-description template is the formulation of metadata requirements which help to establish a common information basis that can be used by the planetary science community to search and understand spatial data products on the level of input data as well as on the level of digital map products. Such a metadata basis therefore forms a way to store information of traditional analog map legends within a digital map product. Such metadata information needs to be implemented as template on two different levels: the individual (vector-based) map level data as well as the (raster-based) dataset level that was used to create the map. Such a metadata template can then be used either in stand-alone GIS projects or it can be integrated into a more sophisticated database model using an XML-structured and standardized vocabulary. The usage of an obligatory map description template facilitates the efficient and traceable storage of spatial data and mapping results on a network level.