To create a Contour study, click the button showing a simple polygon contour:
The form will change to the Contour settings:
The step along the radials is important for Contour studies computed with analytical propagation models such as Bullington, Longley-Rice, or Okumura. The Step Distance determines the resolution of the contour location. In this example, the contour will be located to the nearest 0.1kilometer along each radial. For calculations with statistical propagation models such as FCC Broadcast or Carey, this value is not used, since the calculation is based only on the height above average terrain (HAAT) using the topographic data parameters set in the Topo Data section as described below.
Set the step value on the form:
You can define the azimuths on which you want to compute the contour. For example, suppose you want to compute 72 equally spaced radials. Click the “Number” button:
You will be prompted to enter the number of radials to create:
You will be prompted for the range of the radials from the fixed facility:
When the number and length for the radials have been entered, the program creates the radials for the contour calculation:
You can edit individual values on each radial:
Note the pencil icon at the left end of the row indicating that the value is being edited. You can undo the edit as long as the pencil is displayed by clicking the Esc key on your keyboard and the original value will be displayed.
You can delete a row by selecting it by clicking on the selection button to the left of the row and clicking the Delete key on your keyboard.
You can add individual radials by scrolling to the end of the list to the row with the asterisk (“*”) in the selection button.
When you start typing on that line, a new azimuth record is created:
You can fill in the desired values in each column:
Click another line to move off of the new line so the pencil icon disappears. This is necessary to be sure the new added azimuth is saved.
Click the Sort button if you want to see the radials displayed in order by the azimuths. (The program automatically sorts the radials when the coverage study “Task” is saved, as described below.)
You can also define a range or aperture of azimuths. For example, suppose you are particularly interested in the area to the southeast of the Fixed Facility and you want to compute the contour every 1 degree (instead of every 5 degrees) over that range. Click the Range button:
You will be prompted for the range and increment of the azimuth values:
You will be prompted for the length of the radials to compute for the contour:
When these values have been entered, the new azimuths will be added at the end of the list:
You sort the azimuths to put them in the correct order. In this example, there will be some duplication of azimuths. The original 72 azimuths created rows for azimuths 140, 145, etc., which were 30 kilometers long with a step value of 0.1 kilometer. The range of radials from 140 to 160 also created entries on some of the same azimuths (140, 145, etc.) but with different length and step settings (40 kilometers, 0.05 kilometers).
The program resolves this ambiguity of duplicate azimuth values by always using the longer distance and the smaller step value. This change is applied when you Sort the list:
The contour setting also requires a value for the percentage value to be used in locating the contour on each radial. For example, if you set the value to 90%, the contour will be located on each radial at the location where at least 90% of the computed field strength points on that radial meet or exceed the Required Field value specified in the Mobile Facility Interface.
Note that this percentage value is used for analytical propagation models (Bullington, Longley-Rice, Okumura, etc. Statistical models (FCC Broadcast, Carey, Specialized Mobile Radio) include a percentage value in the propagation model.