Q: How can I use the computed field and shadow study information from TAP 4 in other programs, such as MapInfo.

A: The computed results for propagation studies (including shadowing, field strength values, and coverage contours) are contained in a "results" data base (RDB) for each TAP 4 task.

The RDB files are in the FoxPro and dBase (.dbf) file format. For example, the RDB for TAP task #1 would be R0000001.DBF, etc. Any software that can read .dbf files can use the TAP 4 RDB files by selecting the desired fields from the records in the file.

The fields in each record of the RDB file are listed below:

The "value" field takes on different significance for the various types of studies which use the RDB:

• For radial or tile field strength calculations, the value is the computed field strength value in dBu at the point.
• For shadowing studies, the values reprent a "shadowing ratio", the worst case value along the path to each point of the ratio of the path clearance to the first Fresnel zone
• For contours of constant field strength, the value is the contour value (in dBu); the contour consists of all the points in the file with that same contour value, and (if applicable) the same flags in the description field.

The "description" field has several uses.

• For radial or tile field strength calculations this field contains any warning flags generated by the propagation model used (i.e., Longley-Rice, etc.)
• For contours, the description contains the percentage value associated with the contour, such as "f(50,50)" or "f(50,10)" for Broadcast or Carey contours, or "90.0%" for contours computed for Bullington, Longley-Rice, etc.

Since each RDB file corresponds to a particular TAP task, all of the calculated values in the RDB file are based on the same facilities, the same site, etc. However, the RDB file may contain multiple contours for the same task. For example, suppose the TAP task included calculations of several different contour levels, all saved in the RDB file for that task. To plot the 39 dBu f(50,50) contour in MapInfo, select all the records in the RDB file with the value field equal to 39 and "f(50,50)" in the description, sorted by the azimuth field, and connect the points.