Revit 2010 has included handy new hidden elements in elevations called project base point and survey point in the form of a little circle and a little triangle. If you do not see them in elevation, try showing the hidden elements (i.e. the lightbulb on the bottom of the screen) and then zoom to fit (ZF on the keyboard). When you click on the icons they show information on project coordinates.
The circle, called project base point, is what we want to pay most attention to. It shows you what the angle is to true north and the relative elevation. I have worked on projects where the elevation starts at a random number like 10' - 3/32". Whatever number this starts at, is what Revit treats as Zero elevation. Let me give you some examples, then I will explain in a little more detail how the project base point and the relocate project button relate to each other. It is quite confusing so hang in there.
Examples:
1. Problem:
You designed your project before you had any Topo information, the base elevation says your building is at zero, you put the topography when you are on the zero elevation, you run a string of contour labels across it, only to find they are off by some random number.
Solution:
Follow the steps at the beginning of this blog to find the project base point circle. Click on the circle and it will show you the number that your Topo is off. To remedy this, modify the elev number here (DO NOT use the relocate project command)
2. Problem:
You design your project, you used the relocate project command, and you placed you Topography in the project while you where in your main level plan. Your topography base point will be based on this level's floor. It is now nowhere near the right elevation.
Solution:
Follow the steps at the beginning of this blog to find the project base point circle. Click on the circle and verify that the elevation number is relative to the distance you used to relocate your project. If so, or if not, you may manually change this number back to zero. This will not change the location of your project. If your main level elevation is at 643'-0" it will stay at that elevation. What I do next, is I create a site plan elevation at elevation zero and then building my topography. It should end up in the right place, throw some label contours on it and check it out. If the label contours are still off, play with changing the labels parameters from shared to project and visa versa.
Further Explanation:
THE PROJECT BASE POINT AND THE RELOCATE PROJECT FEATURES do not go both ways. This is where it gets confusing. If you relocate the project (In the project location section of the manage tab under the position pulldown menu) it WILL change the elevation of the project base point. If you change the project base point it WILL NOT change the project elevation. The project base point represents just that, the project base point. This is the base elevation for everything. The tricky part is, if you are not aware of the project base point, the elevations will read correctly, but the labeled contours of your topography will be off by whatever the project base was originally set to when starting the project.
Again to remedy this, manually change the project base point in elevation by clicking on the circle and changing the number to whatever you want it to be. Then, use the relocate project command if you haven't previously done so.
ADVANTAGES of these two elements being independent of each other:
The contour labels can be shown as the ACTUAL elevation, while the building can be shown as a relative elevation to whatever number you choose.
DISADVANTAGES of these two elements being independent of each other:
It can be very confusing when you are trying to show both your building and the contour labels as the ACTUAL values.
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