Presentation Information
[PPS04-P22]Introduction to the Lunar “IN-YOU-ZU”: Improved Topographic Visibility
*Ryotaro Araki1, Yukihide Akiyama2, Yoji Takahashi2, Hiroyuki Sato1 (1.Institute of space and astronautical science, 2.AERO TOYOTA Co.)
Keywords:
Topographic map of the Moon,Terrain representation method,JAXA Virtual Planet
Extending a microtopographic visualization methods to planetary bodies beyond Earth can support geomorphologic investigations. We introduce a global lunar IN-YOU-ZU map that we have developed and released.
IN-YOU-ZU is a microtopographic visualization method developed by AERO TOYOTA Co. [1, 2, 3]. Its drawing algorithm is based on hillshade diagrams rendered using nadir illumination. A conventional hillshade diagram represents topography as illumination and shadow produced by oblique illumination from a fixed azimuth (commonly from the upper-left direction). While oblique illumination facilitates intuitive perception of relief, the visibility of small relief on slopes varies with the slope orientation relative to the illumination azimuth. To remove this directional dependence, IN-YOU-ZU uses a hillshade diagram generated with nadir illumination, so that surface slope is expressed as brightness.
Because nadir illumination suppresses the azimuthal bias of hillshading but makes it difficult to distinguish convex from concave, IN-YOU-ZU represents relative convexity/concavity using colors. Relative to an approximate surface obtained by fitting the topography at a specified wavelength, convex areas are assigned warm hues and concave areas cool hues. Under nadir illumination, slope is expressed as brightness (i.e., steeper slopes appear darker). By compositing multiple hue maps derived from fittings at different wavelengths onto the nadir-illumination hillshade diagram, the IN-YOU-ZU product is generated. Thus, because IN-YOU-ZU expresses slope as brightness and relative convexity/concavity as cool/warm hues, microtopographic information is readily preserved. Compared with conventional hillshade diagrams with oblique illumination, the readability of microtopography on slopes does not depend on azimuth. Moreover, simultaneously representing dynamic regional-scale elevation differences (e.g., mountainous relief on the order of several thousand meters) and much smaller-scale relief (e.g., undulations with elevation differences of several tens of meters or less) is difficult with elevation color maps, but is straightforward with IN-YOU-ZU.
We produced global lunar IN-YOU-ZU maps at 60 m/pixel and 360 m/pixel based on the SLDEM2013 digital terrain model [5]. These products are currently available through JAXA’s 3D GIS web service, JAXA Virtual Planet. The lunar IN-YOU-ZU facilitates intuitive identification of stratigraphic relationships and can be used for geomorphologic and geologic studies, crater chronology, and landing-site assessment for future lunar exploration. Here, we introduce how to use the data and present example applications.
IN-YOU-ZU is a microtopographic visualization method developed by AERO TOYOTA Co. [1, 2, 3]. Its drawing algorithm is based on hillshade diagrams rendered using nadir illumination. A conventional hillshade diagram represents topography as illumination and shadow produced by oblique illumination from a fixed azimuth (commonly from the upper-left direction). While oblique illumination facilitates intuitive perception of relief, the visibility of small relief on slopes varies with the slope orientation relative to the illumination azimuth. To remove this directional dependence, IN-YOU-ZU uses a hillshade diagram generated with nadir illumination, so that surface slope is expressed as brightness.
Because nadir illumination suppresses the azimuthal bias of hillshading but makes it difficult to distinguish convex from concave, IN-YOU-ZU represents relative convexity/concavity using colors. Relative to an approximate surface obtained by fitting the topography at a specified wavelength, convex areas are assigned warm hues and concave areas cool hues. Under nadir illumination, slope is expressed as brightness (i.e., steeper slopes appear darker). By compositing multiple hue maps derived from fittings at different wavelengths onto the nadir-illumination hillshade diagram, the IN-YOU-ZU product is generated. Thus, because IN-YOU-ZU expresses slope as brightness and relative convexity/concavity as cool/warm hues, microtopographic information is readily preserved. Compared with conventional hillshade diagrams with oblique illumination, the readability of microtopography on slopes does not depend on azimuth. Moreover, simultaneously representing dynamic regional-scale elevation differences (e.g., mountainous relief on the order of several thousand meters) and much smaller-scale relief (e.g., undulations with elevation differences of several tens of meters or less) is difficult with elevation color maps, but is straightforward with IN-YOU-ZU.
We produced global lunar IN-YOU-ZU maps at 60 m/pixel and 360 m/pixel based on the SLDEM2013 digital terrain model [5]. These products are currently available through JAXA’s 3D GIS web service, JAXA Virtual Planet. The lunar IN-YOU-ZU facilitates intuitive identification of stratigraphic relationships and can be used for geomorphologic and geologic studies, crater chronology, and landing-site assessment for future lunar exploration. Here, we introduce how to use the data and present example applications.