Lunar Terminator Visualization Tool


The Lunar Terminator Visualization Tool (LTVT) is a free software tool for the intermediate to advanced student of lunar topography. It permits Moon images in a variety of formats to be located, viewed and compared with a uniform set of tools. It also permits highly accurate measurements to be made on those images.

Design Goals

  • Accuracy
  • Configurable and expandable by end user
  • Ease of use


  • Displays orthographic views of the Moon from any user-selected angle
  • Can paint the lunar sphere with a variety of user-supplied imagery:
    • Texture files covering the whole, or a part of, the Moon in simple cylindrical projection
    • Maps in Mercator (e.g., equatorial LAC's), Transverse Mercator (e.g., LTO's) and Lambert (e.g., high latitude LAC's)
    • Any actual photo taken from Earth or space, provided the date, time and camera location are known
  • With optional digital elevation model (DEM) data, can paint the sphere with simulations of the expected pattern of light and shadow for any combination of viewing and lighting angles; including correct projection of the three-dimensional locations of the surface objects.
  • On the painted sphere, can overlay on the dots encoding information specific to particular longitudes and latitudes, including:
    • Nomenclature
    • Point elevations
    • Features of special interest
  • Dot files available for complete current IAU nomenclature and major selenodetic control systems.
  • Accurately plots the theoretical terminator position based on a user-supplied sub-solar point.
  • Interactively displays the sun angle as the mouse is moved over the image.
  • Can accurately compute the viewing and lighting geometry for any date from 1601-xxxx using optional JPL ephemeris files.
  • Infinite zoom capability
  • An unlimited number of instances of the program can be run simultaneously for overlay of images from different sources (similar to Photoshop "layers")
  • Using the optional JPL ephemeris files, can predict past or future times when the terminator will be at a particular location relative to the surface features, based either on solar colongitude or on the sun angle at a particular feature.
  • Can similarly tabulate past and future times when a given surface feature will be seen at a given distance from the disk center (due to varying librations).
  • List of calibrated photos permanently stored on disk. List can be interrogated to automatically locate and display all calibrated photos showing a particular feature, ranked by sun angle.
  • Can also search a list of dates and times of uncalibrated photos to locate ones that could potentially show a given feature with a particular lighting (if it happens to fall with the photo's field).
  • Tools for:
    • Altering Gamma of displayed texture/image.
    • Identifying nearest feature in current dot file.
    • Measuring distances and bearings in kilometers and degrees.
    • Determining surface height differences based on the observed starting and ending points of solar shadows.
    • Determining expected limit of visibility (theoretical limb circle) for a given sub-Earth point.
    • Interactively drawing circles for accurately estimating (and optionally recording) the positions and diameters of circular features.
    • Counting number of displayed dots.
    • Saving annotated version of current screen display.

System Requirements

  • LTVT works only on Windows-compatible PC's
  • It displays best using the "Windows Classic" desktop theme (simple window borders)

Additional Information

This page has been edited 12 times. The last modification was made by - JimMosher JimMosher on Jan 8, 2010 10:59 am