CHLPRAN Enter the desired azimuth and distance specifications. The azimuths may be entered in any order. When you are finished, exit by pressing function key . The radials will be sorted in order of the azimuth values. After the sort any duplicate azimuth values will be deleted. To add an additional radial press . A new radial will beadded after the current cursor position. To delete a radial, position the cursor on the radial to be deleted and press . Note that you cannot delete ALL of the radials. If you wantto change the method of specifying the data to be extracted you can exit from this radial selection window. Even if radials are still shown in the window, these will be replaced by either of the other methods (sequential azimuthsor target coordinates). CHLPCOR Enter the latitude and longitude of the desired target site.The azimuth and distance to each site will be computed. The site coordinates may be entered in any order. When you are finished, exit by pressing function key or the key. The radials will be sorted in order of the azimuth values. After the sort any duplicate azimuth values will be deleted. To add an additional radial press . A new radial will beadded after the current cursor position. To delete a radial, position the cursor on the radial to be deleted and press . Note that you cannot delete ALL of the radials. If you wantto change the method of specifying the data to be extracted you can exit from this radial selection window. Even if radials are still shown in the window, these will be replaced by either of the other methods (sequential azimuthsor selected azimuths). CHELPN1 You have two choices for specifying and/or printing distanceand elevation values: (B)ritish units: feet and miles (M)etric units: meters and kilometers CHELPN2 This program permits two methods of specifying the path to be studied. You may either: * Enter the azimuth and distance from the primary site, OR * Enter the coordinates of a target point at the end of the path CHELPN2A This program accepts radial azimuth(s) and start/stop/step distances for extraction of terrain data. You may specify either: * Sequential radials (e.g., 0, 45, 90, etc.) OR * Selected (random) radials (e.g., 35.7, 241.0, etc.) CHELPN2B Select the range of sequential radial azimuths. You must specify the starting and stopping azimuths, and the increment (or step) value. The azimuths must be between 0 and 360, inclusive. If you want a sequence that starts below 360 degrees and continues through and past 360 you must retrieve the data in two passes. For example, suppose you want only azimuths from 270to 90 degrees in 10 degree steps. You must first extract thedata from 0 to 90, and then from 270 to 350. CHELPN2C For the radial azimuth(s) selected, enter the distances fromthe primary site to start and stop the elevation data, and the distance increment between the data points. The starting distance must be greater than zero. If you wantto start from the primary site, specify a value such as .1 miles or kilometers. CHELPN3 Select the data base to use for this session. Either the 30-second or the 3-second data base can be used. CHELPN4 This program provides three options for interpolating the data from the data base: * The prescribed FCC method using four points from thedata base, OR * A weighted method using twelve data points from thedata base * A non-interpolation "maximum elevation" method. The FCC method is satisfactory for computing terrainAVERAGES, but tends to "flatten" the actual values: peaksappear too low, valleys appear too high. The weighted method includes consideration of thesurrounding slope to improve the accuracy of the individualdata points extracted from the data base, but increasesexecution time, since twelve data base points are usedinstead of four. The maximum elevation method selects the highest of the four"corner" data base grid points around each target point. No interpolation is performed. This method approximates a "worst case" terrain obstruction for the path(s) being extracted. CHELPN5 If you are writing the elevation averages, the result willbe one line for each radial. A typical session of eight ornine radials will fit conveniently on a single pageexhibit. Seventy-two radials will require three pages. You may also elect to write additional information regardingthe elevation data pertaining to the radial(s) under study: You may write the elevation of EACH POINT on the radial. (You may also later elect to write the elevation of each point in an ASCII file. The present selections involve only the output to be printed.) If you print the elevation of each point on the radial you may also write the elevation of each of the four NGDC data file points which form the "corners around the point on the radial which are used to interpolate the radial point elevation. Each of the options will substantially increase the volumeof the output of the program. Eight radials may require 75pages if every point and the corresponding corners areprinted. CHELPN6 Enter the file name extent to be used to save the elevation data. If an existing file is used, new radial data will be added to that file. If a new file extent is used, a new filewill be created. Press to see a list of existing elevation files for this JOB number. Note that adding elevation data to an existing file can significantly increase the program execution time if the newradial azimuth values are below the values already in the file. Radial data is stored sequentially for more efficientuse of the data files by other TAP programs. If lower azimuth values are added, all existing data in the file mustbe rewritten to make room for the new data. Try to write radials in ascending order, or specify a new extent to create a new file. CHELPDSKCHG This program will look for the required elevation data base files according to the paths specified in the system configuation screen. These paths (primary and alternate) arenormally specified as the hard disk or CD-ROM drive. If the required file is not found in either of these paths, the program can prompt you to insert the required floppy disk or CD-ROM disk. However, you also have the option of suppressing this promptasking for another disk. For example, if you want to extract a large amount of data without interruption, answer "N" to this prompt. During the data extraction for each radial, if a data file is not found, no prompt will will be issued for a disk. Some of the required points on the radial will not be included in the resulting file. Note that the data file for the site location MUST be available. If this file is not found and the change disk prompt is suppressed, the program will abort. RADIAL INPUT This program permits two methods of specifying the path to be studied. You may either: þ Enter the azimuth and distance from the primary site, and the coordinates of the end of the radial will be computed OR þ Enter the coordinates of a target point at the end of the path and the azimuth and end ("stop") distance will be computed. You can save target coordinates to a file that can be retrieved later, for example to use the same coordinates to compute radial azimuths and distance from a different site. In either case you must enter a starting distance from the site and a distance step value which will be used to increment the distance for the points along the radial. You can also specify a sequence of azimuths to generate evenly spaced radials with the same start, stop, and step distances. CHELPDATABASE This program currently supports three point-elevation data bases: þ 30-meter data þ 3-second data þ 30-second data The files are searched for each data point in order of decreasing resolution (as shown on the above list) for each data base you select (by answering "YES"). You can also specify the disk change option for each data base independently. For example, if all of your 30-meter data files are on your hard disk in your data path, you can answer "NO" to the disk change option for that data base, but "YES" for 3-second data, so if a data file is needed that you do not have in 30-meter data, you will not be askedfor the 30-meter file. The program will look for the file in the 3-second data and prompt you for the needed CD-ROM ifthe file is not found.