Fix a typo in index.rst

Thanks to Pierre Moulon for pointing this out.

Change-Id: I1e0021b613e57e9f0c13db4634662ee3e1e22aa9

docs/source/index.rst

diff --git a/docs/source/index.rst b/docs/source/index.rst
index 3c05b0d..26b318a 100644
--- a/docs/source/index.rst
+++ b/docs/source/index.rst
@@ -30,7 +30,7 @@
 
 * Estimate the pose of `Street View`_ cars, aircrafts, and satellites.
 * Build 3D models for `PhotoTours`_.
-* Estmate satellite image sensor characteristics.
+* Estimate satellite image sensor characteristics.
 * Stitch `panoramas`_ or apply `Lens Blur`_ on Android.
 * Solve `bundle adjustment`_ and SLAM problems in `Project Tango`_.