Analysis of Mars data using Arcobjects and Modelbuilder

Kurzfassung

Geographic Information Systems (GIS) are powerful tools for integration of different planetary datasets, e.g. images, spectral data, and digital terrain models which are typically given in different formats like vector and raster. We are currently involved in a project to import large volumes of data from the recent Mars missions into a planetary GIS database. Before working in GIS with such datasets, it is necessary to prepare them for import. Using ArcOBJECTS, a collection of ArcGIS programming objects, and object oriented programming languages like Visual Basic .NET, we create ESRI shape files according to a suitable specification. Regular shape files are not sufficient, because data points have often large numbers of attributes associated with them in the original ASCII dataset. Here, the MOLA (Mars Orbiting Laser Altimeter) dataset is a typical example with over 33 attributes per Laser shot. These have to be imported using a .dbf database file. Once this is accomplished, it is possible to combine all these different datasets with raster information, such as HRSC (High Resolution Stereo Camera), or MOC (Mars Orbiter Camera) images, or MDIM 2.1 maps for joint analysis. Subsequently, we have developed an improved method for analysis of volumes for topographic depressions or positive relief features of large extent. ArcGIS Desktop provides a measurement tool with the “Area and Volume Statistics“ module. However, this module is very limited in scope. It is possible to “calculate statistics above plane“ or “calculate statistics below plane“ for volume. This is not accurate enough for measuring, e.g. craters or valleys covering large areas, because the reference surface may not be planar. Furthermore it is not possible to specify a selected area. The software can handle only the entire data set. In our improved measurement tool, we consider the resolution of the underlying digital terrain model, the topographic trend of very large areas and the software allows us to interactively choose defined sub-areas for accurate surface feature analysis of differential levels. We also implemented ArcOBJECTS to define our appropriate solutions for better handling large datasets and also began studying the widespread Martian drainage networks using ESRI`s “ModelBuilder” to automate the time-consuming step by step workflow. The goal is to find pour points to calculate the watersheds, for runoff water only. We have applied our GIS tools for various geologic mapping and interpretation tasks, and for 2d and 3d visualisations and analysis. We will demonstrate several examples to import, measure and project large datasets in different formats with ESRI’s object model for ArcGIS 9.X.