# Tesseroids: forward modeling in spherical coordinates¶

A collection of **command-line programs**
for modeling the **gravitational potential, acceleration, and gradient
tensor**.
*Tesseroids* supports models and computation grids in Cartesian
and spherical coordinates.

Developed by Leonardo Uieda in cooperation with Carla Braitenberg.

**Official site**: http://tesseroids.leouieda.com

**License**: *BSD 3-clause*

**Source code**: https://github.com/leouieda/tesseroids

**Latest release**: v1.2.0 (doi:10.5281/zenodo.16033)

Note

*Tesseroids* is **research software**.
Please consider *citing* it in your publications
if you use it for your research.

Warning

See the list of *known issues* for things you should be
aware of.

The geometric element used in the modeling processes is
a **spherical prism**, also called a **tesseroid**.
*Tesseroids* also contains programs for modeling using
**right rectangular prisms**,
both in **Cartesian** and **spherical coordinates**.

## Getting started¶

Take a look at the examples in the
*Cookbook*.
They contain scripts that run *Tesseroids* and some Python code to plot the
results.

If you’re the kind of person who likes to see the equations
(who doesn’t?),
see the *Theoretical background* and the references cited there.

For a more detailed description of the software, options, and conventions used,
see the *usage instructions*.

Also, all programs accept the `-h` flag to print the instructions for using
that particular program. For example:

```
$ tessgrd -h
Usage: tessgrd [PARAMS] [OPTIONS]
Make a regular grid of points.
All units either SI or degrees!
Output:
Printed to standard output (stdout) in the format:
lon1 lat1 height
lon2 lat1 height
... ... ...
lonNLON lat1 height
lon1 lat2 height
... ... ...
... ... ...
lonNLON latNLAT height
* Comments about the provenance of the data are inserted into
the top of the output
Parameters:
-r W/E/S/N: Bounding region of the grid.
-b NLON/NLAT: Number of grid points in the
longitudinal and latitudinal directions.
-z HEIGHT: Height of the grid with respect to the
mean Earth radius.
-h Print instructions.
--version Print version and license information.
Options:
-v Enable verbose printing to stderr.
-lFILENAME Print log messages to file FILENAME.
Part of the Tesseroids package.
Project site: <http://fatiando.org/software/tesseroids>
Report bugs at: <http://code.google.com/p/tesseroids/issues/list>
```

## Getting help¶

Write an e-mail to Leonardo Uieda,
or tweet,
or Google Hangout.
**Even better**, submit a bug report/feature request/question to the
Github issue tracker.

## Contents¶

- Citing
- Known issues
- Changelog
- Installing
- Releases
- Theorerical background
- Using Tesseroids
- A note about heights and units
- Getting help information
- Computing the gravitational effect of a tesseroid
- The -a flag
- Verbose and logging to files
- Comments and provenance information
- Generating regular grids
- Automatic model generation
- Calculating the total mass of a model
- Computing the effect of rectangular prisms in Cartesian coordinates
- Piping

- Cookbook
- Calculate the gravity gradient tensor from a DEM
- Simple prism model in Cartesian coordinates
- Simple tesseroid model
- Convert a tesseroid model to prisms and calculate in spherical coordinates
- Convert a tesseroid model to prisms and calculate in Cartesian coordinates
- Using tesslayers to make a tesseroid model of a stack of layers

- License