In response to many requests for TV service area data, the Video Division of the Media Bureau, Federal Communications Commission (FCC) will release predicted service contour data points on a regular basis. Generally, updated files will be to the posted the FCC's website by approximately 3 PM each Saturday afternoon, Eastern time. These zipped files will be posted to the following locations (include capital letters and underscores as shown): :

• By http: http://transition.fcc.gov/ftp/Bureaus/MB/Databases/tv_service_contour_data/
• By ftp:   ftp://ftp.fcc.gov/pub/Bureaus/MB/Databases/tv_service_contour_data/

Two files are available:

• TV_service_contour_current.zip
• TV_service_contour_archived.zip

Current files contain data for active records (licenses, construction permits, applications) as shown in the TV Query. Archived data points to records contained in the Media Bureau's CDBS (Consolidated DataBase System) that have been superseded by other records, or that are no longer represent current data. Archived records are not shown in the TV Query, but these records are retained for reference. Most users will only require the current data files. Distances to TV service contours are generated using the effective radiated power in a given direction, and the radial HAAT in that direction, along with the FCC's F(50,50) propagation curves for analog TV stations and the F(50,90) curves for digital TV stations. See FM Propagation Curves and Antenna Height Above Average Terrain (HAAT) Calculations for additional information on this process. USERS TAKE NOTE: the digital TV contours so generated by this procedure may not exactly correspond with coverage predicted by noise-limited service calculations used for DTV allocations work. But these service contours are far simpler to work with and provide a useful representation of DTV coverage.

USERS TAKE NOTE: These files are LARGE! We do not recommend attempting to download these files over a dialup connection, which may take hours. Use a broadband connection, and make sure your system has enough disk space to handle these files. Current data files, unzipped, may be on the order of 220 MB in size.

Because of the files' large size and layout, it can be difficult to find a viewer capable of displaying the entire text file at one time. (The Firefox browser will display the entire file.) However, the structure of the file is straightforward. Each line of these formatted text files is constructed as follows:

707       |FM|KAXE  BLED-1533                    |47.25472 ,-93.43417 |47.76041 ,-93.43417 |47.75997 ,-93.42105 | ... |47.76079 ,-93.44731 |^

where the leftmost number represents the application ID number of the CDBS/TV Query record. The station's service is listed in the next field, followed by the description (call sign and application file number) in effect at the time the service contour data was initially generated. This is followed by the NAD27 coordinates |latitude, longitude| of the station's or application's transmitter site. After the transmitter site coordinates follows 360 |latitude, longitude| pairs, where the first pair is at 0 degrees (true north), clockwise at 1 degree intervals to 359 degrees. An end of record character "^" finishes the line. This makes each line 7,633 characters long. Code to read these lines should be written with the long record length in mind. West longitudes and south latitudes are referenced by negative numbers, in keeping with the conventions of most GIS systems. Regretfully, we cannot honor requests to provide this data in alternative formats.

To associate specific service contour records with the proper station or application data, match the application ID number of the record with the corresponding application ID number from CDBS' application.dat table. Alternatively, (and certainly much easier than deciphering the CDBS tables structures) is to use the TV Query with the output set to create a "pipe-delimited text file". That output can then be parsed in accordance with the fields description file at http://transition.fcc.gov/mb/audio/am_fm_tv_textlist_key.txt to obtain the data most commonly sought by users. Using the TV Query searches also has the advantange of allowing users to winnow out unwanted station records. For example, a TV Query search for all the licensed Class A television stations (service code CA) in Mississippi will exclude station records in other states and services, as well as construction permit and application records.

It must be noted that the station contours here do not always reflect the same predicted field strength value. For analog TV stations, the following table may help:

And similarly, for digital television, service is defined to exist where the received signal strength exceeds the limit shown in the following table, using the F(50,90) propagation curves. These field strength values are defined in Section 73.622 and Section 73.625).

TV service contours usually do not define the outer limit of service. In most cases, a television station may be received at locations outside (and sometimes well outside) the service contours given in these files. Within the service contour, reception is generally protected from interference caused by other stations on the same channel or adjacent channels or frequencies. Outside of that contour, interference may occur from other stations. It simply is not possible, under any rational allocations scheme, to protect each station out to the point at which it cannot be heard or viewed by anyone. Doing so would result in far fewer stations available to listeners or viewers. The Commission's rules represent a balance between very few stations with no interference between them, and great numbers of stations with small service areas and severe mutual interference.

Finally, it must be stated that ALL USE OF THESE CONTOUR DATA FILES IS AT THE USERS' SOLE RISK, and the FCC nor the Federal Government shall be responsible for errors or omissions, late posting of data, or any consequences thereof. (But hey, these files are free.) No restrictions are set on the use of this data. The FCC does not guarantee that the contour data here will correspond to the contour data considered during the processing of given applications. Users should take note that this contour data is only generated once for each application ID number, shortly after the application is posted to the TV Query, so that the possibility exists that subsequent corrections to the CDBS database might not be reflected in the service contours herein. (However, amendments to electronically filed applications will have a new application ID number, and so new contour data will be generated for that amendment.) Archived records will not be corrected; as they are retained for reference purposes only. And lastly, TV interfering contours will not be generated.

Hossein Hashemzadeh, hossein.hashemzadeh@fcc.gov
Video Division, Media Bureau
Federal Communications Commission