User Guide What Files Are Needed - fermigas/ltvt GitHub Wiki

Overview of Files Required for LTVT to Work

LTVT consists of a core program and a number of auxiliary files. It is important to understand that for full functionality, some of these files must be supplied by you, using the simple instructions provided in this guide.

This modular design allows the individual components to be separately updated, and provides the users flexibility in the functions and kinds of displays they want. For example, the core program and help files can be updated without having to download and re-install a large package; and users can pick and choose the JPL ephemeris files that cover the time periods they happen to be interested in. It also permits you to employ LTVT to use/view possibly-copyrighted material which we would otherwise not be able to distribute to you. For example, texture maps from government websites or other lunar mapping programs. This also allows you to set your own limits on what size files you are comfortable downloading/displaying with your internet connection/hardware. Finally LTVT uses files in as accessible form as possible. For example, the lunar feature list and time correction files can be easily modified with any text processor, while the texture reference maps are in JPEG or Windows Bitmap format, which can also be easily altered to the user's tastes with any photo editing software.

Files that are Included

The compressed folder (LTVT__nn_.zip -- where nn is the version number) in which the "complete" version of LTVT is normally distributed contains the following files:

  1. ReadMe.txt : a brief text file listing and explaining the contents of the folder.
  2. LTVT_v_n_n_.exe : the executable program file.
  3. LTVT_UserGuide.chm : the current User's Guide (which is what you are reading) in compiled (machine readable) Windows HTML Help format. This can be opened separately (double-click) or from within the program (go to the Help menu) on any modern Windows PC.
  4. lores.jpg : a basic low resolution shaded relief map of the lunar surface organized by longitude and latitude used for creating simulated texture maps of the Moon as seen in projection.
  5. TAI_Offset_Data.txt : A small text file listing the number of seconds difference between Coordinated Universal Time (UTC) and the time system used for retrieving ephemeris data.
  6. Named_Lunar_Features.csv : a list of IAU sanctioned names of lunar features, used for plotting and identification.
  7. unxp2000.405 : a JPL ephemeris file containing lunar and solar position data for the years 2000-2050.
  8. Observatory_List.txt : a sample list for use by the Set Location form.
  9. PhotoSessions.csv : a sample list for use by the Photo sessions Search utility
  10. land_shallow_topo_2048.jpg : a colored texture of the Earth as seen from space taken from NASA's Visible Earth website for use by the Earth from Moon viewing function.

LTVT has been carefully designed to require only those auxiliary files actually needed for functionality. If a given file is not present, those functions that do not require it will continue to work. The only truly essential file is LTVT_nn_.exe, which, all by itself, is capable of drawing a black and white shaded map disk representing the phase of the Moon and exact position of the terminator as seen from any manually-entered direction in space with the Sun in any other arbitrary direction; and telling you the correct Sun angle and azimuth at each visible longitude and latitude. You can look up the directions from the Moon to the Earth and from the Moon to the Sun in a variety of sources, including the Astronomical Almanac or the free on-line ephemeris service of the Jet Propulsion Laboratory (JPL). LTVT can also draw a crude texture map using the low-resolution file included in the distribution package. However, for convenience and pleasure of use it is highly recommended that you go to the trouble of locating and downloading a few extra files.

Files You Have to Supply

The additional files required to achieve full functionality of LTVT are:

  1. High Resolution Texture Files : the single lunar texture file included as a sample in the LTVT distribution folder is really adequate only for rendering full disk images. As explained in the Step-by-Step Directions you will almost certainly want to add higher resolution textures, such as the high resolution hand-painted shaded relief map and Clementine photographic mosaic, available from the distributors of VMA.
  2. Additional JPL ephemeris files: these files allow LTVT to automatically compute a highly accurate lunar geometry for any date, time and observer location you specify. A separate 4.7 MB download is required for each 50-year long block of time from 1600 to 2200. The files contain highly precise, machine-readable look-up tables of the positions of the Sun, Earth and Moon in a rectangular coordinate system, as well as the orientation of the Moon's inertial axes in that system. Please note that LTVT has no capability for calculating lunar geometries in the absence of these files, so if you want an automatic computation of the viewing/lighting conditions you must download the appropriate JPL files. The exact files you need will depend on the years you are interested in. LTVT will tell you the names of the files that it requires. Follow the Step-by-Step Instructions for downloading them from the JPL FTP site.
  3. Maps and Images: a key feature of LTVT is its ability to compare lunar data from a variety of sources including maps and Earth-based and satellite photos of the lunar surface. See the LTVT website for directions on how to obtain and use these products.
  4. Digital Elevation Model: LTVT can create simulations of the Moon's appearance based on computer models of the surface height at selected longitudes and latitudes. Currently, it can read the moderate resolution global and high resolution polar DEM's available from the Kaguya project in Japan.

These files are all freely available.

Files that LTVT will Create

At your request LTVT will create the following files:

  1. LTVT.ini : a simple text file, which you can edit with any text processor. This is created in the LTVT folder when you invoke the Files...Save Options... menu item in the Main Window. It contains such information as the paths to the auxiliary files and whether you want to draw maps with dots or textures on start-up. If you delete this file, the defaults will be automatically restored.
  2. Saved Images : LTVT can save the simulated Moon image you see, exactly as it appears, to a disk file. You may select either JPEG or Windows Bitmap format. The reproduced image window will include annotations at the top and bottom giving all information necessary to reproduce the view; and also, if the geometry was computed, the date, time and observer location that were used. Such image files can be saved to the LTVT folder, or anywhere else you choose. Saved image files are created using the Save Image button in the lower right of the Main Window.
  3. Dot Files : the Circle Drawing Tool has the optional capability of storing the current circle position and diameter in a dot file. This is a simple text file created in the current LTVT working directory and given the name CircleList.txt. Internally it is in a comma-separated value format, but it can be opened with any text processor and can be deleted when no longer wanted, or when wants to create a new Circles.txt. As long as the file exists, new circle data will be appended to it. If it does not exist, a new file will be created as needed. No control is provided over the name or location of this file.
  4. Shadow Measurement Files : the Circle Drawing Tool also has an option to create a Shadow Measurements file. This is also a simple text file created in the current LTVT working directory, and in comma-separated value format. It is given the name ShadowProfile.txt, and lists the results of shadow measurements recorded with the Right-click menu using the Record shadow measurement option (when available). It can be deleted when no longer wanted. As long as a file of this name exists, new shadow measurement data will be recorded to it. If it does not exist, until a new shadow measurement file is created with the Circle Drawing Tool, the shadow measurement data is recorded only on the screen. No control is provided over the name or location of this file.

LTVT does not write to or corrupt your system registry.