This is a Wikipedia discussion of the Cosmic Distance Ladder, the first step of which is examined in this BLOSSOMS lesson.
http://en.wikipedia.org/wiki/Cosmic_distance_ladder
This is a Wikipedia entry on the Parallax, a displacement or difference in the apparent position of an object viewed along two different lines of sight
http://en.wikipedia.org/wiki/Parallax
This is a discussion on the European Space agency website about Gaia, the ambitious mission to chart a three-dimensional map of our Galaxy and the Milky Way.
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=26
This is an educational page on the website of the European Space Agency with a wealth of educational resources about space mission, Gaia.
http://www.esa.int/Education/Little_Books_of_Gaia
This is a Wikipedia entry on the satellite Hipparcos, the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky
http://en.wikipedia.org/wiki/Hipparcos
This is an educational page on the website of the European Space Agency about the space mission, Hipparcos.
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=20