# 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**: v1.2.1 (doi:10.5281/zenodo.582366)

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