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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012 
XXII ISPRS Congress, 25 August - 01 September 2012, Melbourne, Australia 
DIGITAL ELEVATION MODELS AND DERIVED PRODUCTS FROM LROC NAC 
STEREO OBSERVATIONS 
K.N. Burns“, E.J. Speyerer“, M.S. Robinson“, T. Tran“, M.R. Rosiek b , B. A. Archinal b , E. Howington-Kraus b and the 
LROC Science Team 
“ School of Earth and Space Exploration, Arizona State University, 1100 S Cady, Tempe AZ 85287 - 
(knburns 1 @asu.edu) 
h Astrogeology Science Center, United States Geological Survey, 2255 N Gemini Dr, Flagstaff AZ 86001 -(mrosick, 
barchinal, ahowington)@usgs.gov 
Commission IV, WG IV/7 
KEY WORDS: DEM/DTM, Three-dimensional, Application, Planetary, Mapping, Geomorphology, Modeling, Processing 
ABSTRACT: 
One of the primary objectives of the Lunar Reconnaissance Orbiter Camera (LROC) is to acquire stereo observations with the 
Narrow Angle Camera (NAC) to enable production of high resolution digital elevation models (DEMs). This work describes the 
processes and techniques used in reducing the NAC stereo observations to DEMs through a combination of USGS integrated 
Software for Imagers and Spectrometers (ISIS) and SOCET SET® from BAE Systems by a team at Arizona State University (ASU). 
LROC Science Operations Center personnel have thus far reduced 130 stereo observations to DEMs of more than 130 stereo pairs 
for 11 Constellation Program (CxP) sites and 53 other regions of scientific interest. The NAC DEM spatial sampling is typically 2 
meters, and the vertical precision is 1-2 meters. Such high resolution provides the three-dimensional view of the lunar surface 
required for site selection, hazard avoidance and planning traverses that minimize resource consumption. In addition to exploration 
analysis, geologists can measure parameters such as elevation, slope, and volume to place constraints on composition and geologic 
history. The NAC DEMs are released and archived through NASA’s Planetary Data System. 
1. INTRODUCTION 
1.1 LROC 
The Lunar Reconnaissance Orbiter Camera (LROC) consists of 
two narrow angle cameras (NACs) to provide 0.5 - 2.0 meter- 
scale panchromatic images of a 5km swath and a wide-angle 
camera (WAC) to provide images at a pixel-scale of 100 meters 
in seven color bands over a 60km swath (Robinson et al. 2010). 
The NAC was not designed as a stereo system, but obtains 
stereo pairs through images acquired from two orbits, with the 
spacecraft making at least one off-nadir slew (Figure 1). Stereo 
observations are nominally obtained on consecutive orbits in 
order to minimize lighting changes between observations. 
Slewing the spacecraft off-nadir interferes with data collection 
from other instruments, so LROC slew opportunities are limited 
to four per 24 hour period. Slew angles range between 0° and 
30° and a convergence angle between images is typically 
between 10° and 45°. 
1.2 DEM Production 
This paper describes the production and release of NAC DEMs 
produced by the ASU team. However, NAC DEM production 
is carried out at various other institutions affiliated with the 
LROC team, including U.S. Geological Survey (USGS), NASA 
Ames, Jet Propulsion Laboratory (JPL), University of Arizona 
(UA), Ohio State University (OSU), and the German Aerospace 
Center (DLR) (Cohen et al. 2008). ASU, USGS, NASA Ames, 
and UA all use SOCET SET from BAE Systems (DcVenecia et 
al. 2007) for photogrammetric processing of NAC images. 
NASA Ames is using their Stereo Pipeline (Moratto et al. 2010) 
and OSU is using their Orbital Mapper and Leica 
Photogrammetry Suite 9.3. DLR uses photogrammetry software 
developed in-house (Oberst et al. 2010). 
2. DATA SOURCES 
Figure 1. Diagram Illustrating NAC stereo image acquisition. 
2.1 LROC NAC 
The LROC NACs are linear pushbroom cameras built using the 
Kodak KLI-5001G line array. The line array is a 5064 element 
charge coupled device (CCD) with 7-micron pixels. The two 
NAC cameras are designated NAC-Left (NAC-L) and NAC- 
Right (NAC-R). The NACs are mounted on the spacecraft such 
that the CCDs are perpendicular to the spacecraft’s X-axis. 
Each camera is designed to provide 0.5 meter pixel scale 
panchromatic images covering a 2.5 km swath cross-track, for a 
combined coverage of 5 km, at an altitude of 50 km. Each 
camera has an internal buffer of 256MB; allowing for an image 
length of 52,224 lines or 26,112 meters at the native resolution.