The BPIP GEP analysis mode is used to quickly identify all the single-tiers and tier-groups that are close enough to influence a stack.
| • | Select the mode by clicking on "BPIP GEP - Select Stack & Wind Direction" in the Mode List. |
| • | Select a stack by either clicking on it's name in the Stack List or directly clicking on the 3D stack with the left mouse button. Notice how the Wind Direction Arrow appears pointing out from the Stack Top. |
| • | Center the stack in the view by positioning the cursor on the stack and clicking the right mouse button. Rotate the view by clicking down with the left mouse button and dragging the mouse left/right and up/down. |
| • | Rotate the wind direction by clicking down with the left mouse button, anywhere on the Wind Direction Slider, and dragging the mouse left/right to rotate CW/CWW respectively. Notice how the Wind Direction Arrow rotates around the stack, pointing in the Selected Wind Direction. |
| • | Notice what happens while rotating the wind direction: |
| 1. | Anytime the stack is found to be within one or more GEP-SIZs, the single-tier or tier-group that produces the highest GEP value will be displayed and highlighted with a combination of three colors: blue, orange, and yellow. A single-tier will be blue. A tier-group will have a Focal Tier colored blue, a Common Height Tier colored orange, and additional Other Tiers colored yellow. If a tier-group has only a single blue tier with one or more yellow tiers then the Focal Tier is also the Common Height Tier. |
| 2. | The associated GEP-SIZ will be displayed in either yellow or blue. Blue if the GEP-SIZ is for a single-tier and yellow if the GEP-SIZ is for a tier-group. Notice that the cross-wind width of the GEP-SIZ is exactly equal to the profile width of the influencing structure (i.e. the single-tier or tier-group). Notice that the length of the GEP-SIZ extends '5L' (where 'L' is the lesser of the influencing structures height or width) past the downwind boundary of the influencing structure. |
| 3. | The computed GEP Height will be displayed as a yellow or blue cylinder on top of the Selected Stack cylinder. The GEP Height cylinder will be blue if it is produced by a single-tier and yellow if it is produced by a tier-group. |
| 4. | Notice how the tiers in a tier-group move up and down vertically to align their bases with the Focal Tier. This is necessary to demonstrate that BPIP does not use tier elevation values when combining tiers into groups. All tiers are assumed to have the same base elevation as the Focal Tier. |
| 5. | Notice that the height of the GEP-SIZ block is always equal to the height of the Common Height Tier and that the GEP Height will be "1.5 times the lesser of the GEP-SIZs height or width" above the top of the GEP-SIZ block. This is, in fact, how GEP height is calculated. |
| • | To automatically rotate the Wind Direction and the view direction hit the "Z" key. Hit the 'Z' key again to stop the Automatic Rotation Mode. This 'animation' mode is very useful for observing the GEP height results for all wind directions. Notice that you can perform all other interactions while in Automatic Rotation Mode. Right mouse click on other objects to reset the center of rotation. Pan the scene by clicking down with the middle mouse button and dragging left/right and up/down. Click on another stack, or click on another stack in the Stack List, to select another stack. Even change the analysis mode by clicking on another selection in the Analysis Mode List. |
| • | Use the Display Menu, or Toolbar Buttons to toggle between the 3D and 2D top-down views. Notice in the top-down view how perspective distortion is removed making it easy to see the GEP-SIZ boundaries. Also, use the Display Menu or Toolbar Buttons to toggle the Axes and Grid display On/Off, and to Reset View (i.e. center the entire scene into view). |
Page url:
http://www.breeze-software.com/prod/aermod-isc/help/index.html?gep___select_stack.htm
