On Monday 05 January 2009 12:34:48 Robert H. Bushnell wrote: > Tom, > You argue too much. You want science to do public policy. I want > simple examples. I say use millimeter. Example: Say I build an > intersection of roads. I lay out the curbs in millimeters, 30 000 mm > apart. > Then I place the posts to hold the traffic lights, again in millimeters, > say 2 000 mm from the curb. Next I put down the bolts to hold the posts, > 400 mm apart. All the post hardware is in millimeters. But say some > drawing shows the road in meters and centimeters, possibly 6 276.34 m or > 627634 cm with the bolt centers spaced in millimeters. Having both > centimeters and millimeters on a drawing is risky. They are too close > in size. A unit size ratio of 1000 makes errors unlikely. > But Tom, thanks for your attention to these matters.
Horizontal dimensions in surveys are in meters to the nearest millimeter. Elevations are more likely to be to the nearest centimeter, but are still written in meters. 6276.34 m sounds like a distance along a road. This is written, for reasons unknown to me, as "6+276.340", where the initial 6 is called a station. Pierre
