We present an analysis of Galactic halo structure and substructure traced by \sim 500 RR Lyrae stars in the SDSS stripe 82 region .
The main result of this study is a 2D map of the Galactic halo that reaches distances of 100 kpc and traces previously known and new halo substructures , such as the Sagittarius and Pisces tidal streams .
We also present strong direct evidence , based on both RR Lyrae and main sequence stars , that the halo stellar number density profile significantly steepens beyond 30 kpc from the Galactic center .
Using a novel photometric metallicity method that simultaneously combines data for RR Lyrae and main sequence stars , we show that the median metallicity of the Sagittarius trailing stream in the SDSS stripe 82 region is { [ Fe / H ] } = -1.2 \pm 0.1 dex .
In addition to these results , we will present ongoing work on a 3D map of the Galactic halo constructed using a sample of \sim 4000 RR Lyrae stars that covers 8500 deg ^ { 2 } of northern sky and probes up to 30 kpc from the Sun .