The WebGeocalc tool (WGC)
provides a web-based graphical user interface to many of the observation geometry computations available from the "SPICE" system.
A WGC user can perform SPICE computations without the need to write a program; the user need have only a computer with a standard web browser.
Starting December 13, 2018, NAIF now offers a second
instance of WebGeocalc, operating on a server named WGC2. This instance is the same as the original, described below,
except that it also offers a RESTful (programmatic) interface to the tool, accessible from a script on your computer.
When using this RESTful interface there is no human interaction involved.
There is API documentation describing
how to use this RESTful interface, including some examples. This same documentation is also available via a link named
"API Docs" seen at the top-right portion of each WGC2 page. This second instance of WGC can also be used via GUI controls,
as for the first instance, described below.
A WebGeocalc Tutorial (PDF format) provides an introduction to this tool.
The WGC server is built upon the Toolkit code available from the NAIF server; it merely provides another kind of interface to that code.
WGC can support NASA's planetary projects and planetary data research in several ways.
- It offers much of the SPICE computational capability to those unable to write programs
- It offers a mechanism that scientists and engineers may use to help verify their own SPICE-based code
- It provides a quick and easy means for peer reviewers of science data archives to spot check many of the observation geometry computations included in the archive
- It provides a means to obtain a quick answer to a geometry question arising during a meeting (if the needed SPICE kernels are available to WGC).
WGC makes the job of computing many kinds of observation geometry quicker and somewhat easier than if one has to write a program to do so. A modest amount of HELP information is provided within the tool. Nevertheless, the user must have some understanding of the concepts and terminology used in the field of planetary science, and in SPICE.
NAIF has prepared three examples of using WGC, one that is quite trivial, a complementary pair that are fairly simple, and a third that is somewhat challenging. Users of WGC are encouraged to make use of these examples as training aides.
NAIF also provides a summary of some of the most common problems and errors encountered by early users.
These are found towards the end of the WebGeocalc Tutorial mentioned near the top of this page.
(By far the most common problem is when the user tries to make a computation outside of the time bounds
of the data available to WGC.)
If you are unable to access WebGeocalc it is possible your institution's firewall is blocking traffic to/from port 8443 in an attempt to prevent infection from malware or viruses being downloaded. NAIF cannot help with this–you need to talk to your System Administrator to get help with unblocking that port. (Try Googling "unblock port 8443" to learn more.)