THE LUNAR SUBPOLAR RELIEF MAP: THE WAYS AND TECHNIQUES OF COMPILING AND USING
E.N. Lazarev1, Zh.F. Rodionova2
The lunar subpolar regions are the most interesting for investigations due to such formation as “cooled traps” where water ice is suggested. That is why the compiling of relief map at these areas with high accuracy is the necessary to find out these features of the lunar subpolar regions.
Usually to obtain topographic information the data of laser altimeters and the analysis of stereoimages are used. To compile the lunar relief map of subpolar regions limited by ±60° parallels in polar stereographic projection the next data were used:
- heights being the database of 1036800 high-altitude points with the precision of 0,25î obtained by Clementine spacecraft at all lunar surface (the coordinates and high information were the attributes of each point);
- heights of the lunar Subpolar Regions obtained from the map, compiling by A.C. Cook et. al.; at this map the changes of color are the changes of brightness (from zero to 256), which were counted into heights by the next formula: h = 75·I – 8700 (h – point height, I – point brightness).
The map compiling process consisted of several stages:
- the source brightness map raster image was referenced;
- the raster was exported to GRID-format;
- the database, which one line contains the representation of one image pixel information (coordinates of a pixel center and brightness of it) was obtained;
- the database obtained was edited and generalized;
- point shape-file in stereographic projection was created;
- the brightnesses were counted into heights by formula having been shown above;
- geographic coordinates having been in shape-file attribute table at first (in meters) were counted into projected (spherical) coordinates (in degrees);
- data obtained and Clementine data were joint and correlation of it was counted;
- contours were constructed;
- shaded relief was added;
- the final compiling and development of general map composition.
The entire work at all subsequent stages of map compilation were made with the help of ESRI software products ArcGIS v9.0 and ArcView v3.3.
With the help of the created map the qualitative and quantitative analysis of subpolar lunar surface was fulfilled and some different height profiles were constructed.