I went to the DemoCamp at the Accelerator Centre tonight. Hiro came. I saw Chris E., Alex M., Jesse R., Simon W., Kurtis, and others.

• Simon demoed his Saxite
• Adam deshowed the new sublet board for UW Housing
• Jesse ran through the new UW events
• Christoph described his program to parse information from the web for his employer’s marketing data
• Kurtis from Miovision talked about their image processing technology
• Neil asked the audience a few survey type questions for his company’s voip project

It was good and interesting. I want to go to the next one.

Afterwards some of us went to the Duke of W and some of those had wings and beer.

Did you ever look at the arrows on the road and thought they looked weird? I have.

Clearly they are made for drivers to see and not me standing over them. When close up they look all stretched out. I wondered at what distance they are supposed to look normal. The straight ones are just stretchy, but the one that indicate a turn have the length of the arrow along two axes. If we assume that the horizontal part is supposed to appear with the same length as the vertical we can calculate the angle of view at which the projection of the image will look normal.

So, with my feet, Imeasured the width of the two parts of the arrow. One foot length across.

Two and a half across the other part.

So you can see in the diagram that we have similar triangles. One being the dimensions of the arrow and the other being the dimensions of the triangle between the driver’s eye, the road and the arrow.

Side b of the small triangle is (2.5^2 - 1^2)^0.5 =~ 2.291
So, the distance from the arrow when it appears normal is 2.291 * (the height of the driver’s eyes).

Say the driver’s eyes are 1.5 metres from the road than it would be at 3.4365 metres.