- By http: http://www.fcc.gov/ftp/Bureaus/MB/Databases/tv_service_contour_data/
- By ftp: ftp://ftp.fcc.gov/pub/Bureaus/MB/Databases/tv_service_contour_data/
The data is contained in one large file:
The file contains data for active records (licenses, construction permits, applications) as shown in the TV Query. Some analog TV station records for low power TV and TV translators are included, pending their expected transition to digital operations in 2015.
Using the FCC's F(50,90) propagation curves, distances to digital TV service contours are generated from the effective radiated power in a given direction, and the radial antenna height above the average elevation of that same radial. See TV Propagation Curves and Antenna Height Above Average Terrain (HAAT) Calculations for additional information on this process.
USERS TAKE NOTE: The digital TV contours generated by this procedure may not correspond exactly with the coverage predicted by noise-limited service calculations used for DTV allocations work. However, these service contours are far simpler to work with and provide a useful representation of DTV coverage.
PLEASE ALSO NOTE: The files are LARGE! We recommend using a broadband connection, making sure your system has enough disk space to handle these files. Current data files, unzipped, may be on the order of 105 MB in size.
Because of its large size and layout, it can be difficult to find a viewer capable of displaying
the entire text file at one time. However, the structure of the file is straightforward. Each
line of these formatted text files is constructed as follows:
8 |TX|W04AE BLTT-1002 |43.05646 ,-74.92237 |
... (359 lat, lon points, then) ... | 43.06874 ,-74.92237 |^
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 NAD83 coordinates |latitude, longitude| of the station's or application's transmitter site. Then there are 360 |latitude, longitude| pairs, with the first coordinate pair corresponding to the contour location at 0 degrees (true north) from the transmitter site, and continuing clockwise at 1 degree intervals to 359 degrees. An end of record character "^" finishes the line (to help users detect broken lines). 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) use the TV Query with the output type 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/newsite/datafiles/am_fm_tv_textlist_key.txt to obtain the data most commonly sought by users. Using the TV Query searches also has the advantage 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 permits and application records.
It must be noted that the station contours here do not always reflect the same predicted field strength value. 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).
|Channels||DTV Noise-Limited Service|
|Channels 2 through 6||28 dBu|
|Channels 7 through 13||36 dBu|
|Channels 14 through 69||41 dBu|
And for records pertaining to analog (non-digital) low power TV, TV translator, and some foreign TV stations:
|Channels 2 through 6||47 dBu|
|Channels 7 through 13||56 dBu|
|Channels 14 through 69||64 dBu|
The digital TV service contours available here may not exactly define the outer limit of noise-limited DTV service, but they will be close to it. But 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 is not possible 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 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, USE OF THESE CONTOUR DATA FILES IS AT THE USER'S SOLE RISK, and the FCC nor the Federal Government is responsible for errors or omissions, late posting of data, or any consequences thereof. 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. Lastly, TV interfering contours will not be generated.
Hossein Hashemzadeh firstname.lastname@example.org
Deputy Division Chief
Video Division, Media Bureau
Federal Communications Commission
- FM Service Contour Data Points (includes FM, LPFM, and FM translators)
- AM broadcast service contour data is not available, and we have no time frame for posting this information.
Reviewed: November 4, 2014