We will start with an icosahedron, as most geodesic domes are based on this basic form. Icosahedrons have 20 equilateral triangle faces that form very roughly a sphere. If you look at the example you will notice that all the struts are the same length and all the triangles are the same size, quite a beautifully simple start point for building a dome. All frequency domes can be traced back to this basic form, which can be classed as a 1v geodesic sphere.

To increase the frequency we have to do two things, first subdivide a face into more triangles then project out the vertex of each triangle to an imaginary sphere encompassing the dome. See diagram below:

Higher frequency domes just have more subdivisions; the diagram below shows how 1v, 2v, 3v, and 4v spheres are subdivided. Notice how only even frequencies have a dividing line exactly across the centre of a sphere, while odd frequency spheres have to be divided slightly above or below the centre line. This is why 3v domes don’t have a flat base and come in 4/9th or 5/9th versions.

The greek letter for Phase or frequency is Nu or Nv written N in latin the lowercase (ν) is used as the symbol for spatial frequency of a wave in physics and other fields, a measure of how often components of a structure repeat per unit of distance. Basically the v in 3v stands for frequency.

OK now that you know a little about dome frequency take a look at the dome below and work out what frequency it is. If you need a clue…Find the centre of a pentagon and count how many struts there are to the centre of any other pentagon. Click the image to find the answer.

Related pages:
Pseudo frequency dome geometry explained