FRS/GMRS Radio Mapping Guide

A sample of a team's (in this case, St. Johns) radio propagation map.

Radio mapping is the process of creating a visual representation of radio signal strengths and coverage areas across specific geographic locations. A radio map highlights areas with strong, weak, or no signal, helping organizations understand coverage patterns, identify dead zones, and optimize communication infrastructure. Creating and keeping updated a radio propagation map of a team's Service Area is an important part of disaster response planning in NET.

The purpose of this job aid is to take radio propagation mapping "soup to nuts" and guiding volunteer team leaders through creation and maintenance of a Team Service Area radio propagation map they can include in their Earthquake Response Framework.

Introduction to Radio Mapping

Scenario and Objectives

A disaster has struck the Portland metropolitan area. Routine communications methods (e.g. cell phones) are disabled, and NETs are self-deploying to their Staging Areas/Incident Command Posts. After making some initial assessments, Incident Team Leaders begin deploying strike teams to render aid in the surrounding neighborhoods.

After dispatching a strike team to travel a specific route, the Incident Team Leader discovers they cannot establish FRS/GMRS radio communications with them. Time passes and nothing is heard. Is the team in a radio dead zone? Have their radios failed? Is the team in trouble? Should the Incident Team Leader dispatch a runner to their last known location? Does the strike team need the assistance of a follow-up strike team? Where are they?

Meanwhile, the strike team discovers they can no longer communicate with the NET Incident Command Post. How can they reestablish communications? Should they double back to the last point of communication, risking wasted time and physical exertion? Should they continue forward and hope to reestablish communications at a future location? How long will that take? If the team is in serious trouble, should they detour from their route to call for help? If so, in which direction?

The general purpose of FRS/GMRS radio mapping is to provide solutions for addressing these types of questions in an already stressful situation. FRS/GMRS radios are helpful communications tools, but they have known limitations; particularly range and signal strength.

There are two reasons for developing a radio propagation map. First, it is important to have a realistic idea of what the limits of your radios are. Every team needs to know where this kind of communication can be relied on and where other means of communication, such as runners, will be necessary. Second, you will discover that a relay station, strategically located according to the topography and obstacles in your specific area, can provide a way to link operators to one another.

Acronyms and Technical Terms

The table below lists acronyms and technical terms relevant to this article. Note that some terms below may have a different meaning in contexts outside this article.

Acronym or technical term	Definition
DAQ	"Delivered Audio Quality", a measure of audio quality over a transmission medium (such as radio waves). You can read more about DAQ at https://en.wikipedia.org/wiki/Delivered_Audio_Quality
FRS	"Family Radio Service". You can read more about FRS/GMRS radios in the NETwiki article titled FRS/GMRS Radio - General.
GMRS	"General Mobile Radio Service". You can read more about FRS/GMRS radios in the NETwiki article titled FRS/GMRS Radio - General.
Rover	A volunteer or team of volunteers moving to different points on a predetermined route and using radio to check in with the exercise lead when they arrive at each point. The DAQ of their signal supplies the data that is mapped onto a propagation map.
Scribe	For the purposes of creating a radio propagation map, a scribe is paired with a radio operator at a fixed point. The scribe records the DAQ from strike teams as they check in from different locations.

Method

The process of FRS/GMRS propagation mapping is relatively straightforward and can involve all members of a team. This article structures the method as a formal team exercise to help ensure accurate results. However, PBEM encourages Team Leaders to take a more informal approach as suited to the mood and availability of team members.

FRS/GMRS propagation mapping is conducted by placing a two-person team (a radio operator who is also the exercise lead, and a scribe) at the team's planned NET Incident Command Post. "Rover teams" report to the exercise lead as they stop at specific locations throughout the NET Service Area. The exercise lead and the rover teams record the radio voice quality (DAQ) for the conversation, as they heard it, at each location. The radio voice quality values for each reported location are then used to create color-coded maps for Incident Command staff and strike teams for use during large-scale disaster response.

Goals

The primary goal of a Radio Coverage Survey is to measure the radio voice quality of FRS/GMRS radio communications within a prescribed NET Service Area.

The radio voice quality values may be used to:

• Validate prospective primary and backup locations for a NET Incident Command Post;
• Determine radio voice quality at points throughout the NET Service Area;
• Scope out potential locations for an FRS/GMRS repeater or relay sites.

The process of radio mapping with team members will also:

• Improve radio skills;
• Increase familiarity of the NET Service Area;
• Allow practice of elements of the Incident Command System (ICS);
• Build team cohesiveness; and,
• Cultivate an understanding of radio communication coverage patterns to reduce uncertainty and anxiety during a major disaster.

Radio Coverage Survey Sessions

A team working together can accomplish a Radio Coverage Survey Session in a series of one-and-a-half to two-hour periods. These short sessions enable more volunteers to participate and may be scheduled any time or day of the week.

Several documents available here for download and printing can facilitate a Radio Survey. They include:

Document	Download	Last Update
Radio Coverage Survey Action Plan	[PDF]	2024.11.10
Radio Survey - Command/Listening Post Log	[PDF]	2024.09.20
Radio Survey - Rover Team Log	[PDF]	2024.09.19
Survey area maps
NET Form 2A Personnel Check In	[PDF]
NET Form 3 Team Leader Assignment Tracking Log	[PDF]

Radio Coverage Survey Action Plan

The key elements of a Survey Action Plan should include, at the minimum:

• “What we are going to do”: the goals and plan for the survey;
• “Who is responsible for doing it”: participant assignments;
• “How do we communicate with each other”: survey radio protocols; and
• “What is the procedure if someone is injured”: work in pairs, apply first aid, and contact Command Post and/or 911 as need be.

Additional elements of the Survey Action Plan should include instructions for using Survey Log forms and Survey Area Map.

The Radio Coverage Survey Action Plan, including radio protocols, should be reviewed with survey participants in a NET meeting before the first radio mapping session. Additionally, survey participants should review the action plan before each session. A sample Radio Coverage Survey Action Plan is available as a fillable form in the table above or download here, and can be modified for the NET Service Area surveyed.

Command/Listening Post Radio Log

The Command and listening posts use the Command/Listening Post log to record radio voice quality values of rover team communications. This form should include the date, location, survey radio operator and scribe names, radio type (FRS or GMRS), and radio make and model.

The following information is recorded for each survey location:

• Time (use military time)
• Rover team name
• Location (by cross streets, street address, or other place name)
• radio voice quality value

A sample Command/Listening Post Log is located in the table above, or here.

Survey Area Map

The radio mapping exercise organizer can use My Google Maps or a similar application to create survey area maps identifying key locations. Those locations being:

• Survey Command Post
• Any listening post(s)
• Rover team survey locations

Survey area maps should be prepared in advance and distributed to rover teams at the beginning of the mapping session by the Command Post scribe. Rover teams use these maps to identify survey locations and determine the most efficient path of travel between locations.

A guide to using My Google Maps to create survey area maps is located here. A sample survey area map is located HERE.

Rover team survey locations

PBEM recommends that rover team survey locations should be selected to form a uniform grid across the NET Service Area. A uniform grid is most easily constructed in areas where streets are arranged in a uniform rectilinear pattern. In this situation, survey locations may be places at street intersections. Where long blocks break up a uniform pattern of intersections, survey locations may be placed at specific addresses.

In areas where streets follow elevation contour lines, survey locations may also be placed at specific street addresses or other easily identifiable locations. These locations may be where streets change directions, traverse abrupt changes in terrain, or pass by a distinguishing landmark.

The distance between survey locations should be short enough to eliminate ambiguity in the radio voice quality values in a region. In general, in NET Service Areas with relativity flat terrain, survey locations may be spaced further apart than in areas where elevation changes may obstruct radio signals. Some experimentation may be required to determine the best distance between survey locations. The distance between survey locations may differ in different parts of a NET Service Area.

Taking measurements at too many locations is more advisable than skipping locations and introducing uncertainty into the results.

Radio Mapping Roles

Survey Command Post

The Survey Command Post should be located at the Primary Incident Command Post as specified in the NET Operations Plan. However, radio coverage surveys may be used to evaluate the suitability of other locations if the Primary Incident Command Post has not been established or is being evaluated for relocation.

The Command Post should be staffed with at least two participants: one person acts as the Survey Radio Operator (SRO), and the other acts as a Scribe. The SRO and Scribe collaborate to decide on a radio voice quality value and other rover team information being recorded on the Command/Listening Post Log form by the SRO. The Scribe complete a separate log form to help collaborate on the information received. The Scribe may also check off each reported Survey Location on a copy of the reporting team’s Survey Area Map. The SRO’s log form should be considered to be the official record and the Scribe’s copy as an aid.

During initial sessions, it is preferable to have the Team’s Amateur Radio Operator (ARO) be the SRO. The ARO should brief participants on effective radio protocol. Other participants should act as the SRO during later sessions to gain experience in the Incident Command Post Neighborhood Radio Operator (NRO) role. If the workload overwhelms the ARO, the NRO role may be established. The NRO would be responsible for all NET FRS/GMRS communication in the Service Area.

Rover teams

Each Rover Team should have a minimum of two participants: the Driver/Scribe and the Navigator/Radio Operator who provides directions to each Survey Location.

After arriving at a Survey Location and parking safely, the Navigator/Radio Operator steps out of the vehicle and radios the Command Post. Meanwhile, the Driver/Scribe records the time and location on the Rover Team Log form. After location information has been communicated to the Command Post, the Rover Team agrees on and records a radio voice quality value before proceeding to the next Survey Location.

Measured locations are checked off on the Radio Survey Map as the Rover Team progresses through their assigned Survey Area. The Navigator/Radio Operator may use a map application on their mobile phone to clear up any ambiguity in Survey Locations or for any navigation issues.

When the Rover Team reports its last Survey Location, it informs the Command Post that its survey is complete and that they are returning to the Command Post.

Listening post - optional

Listening posts are optional but may be placed at locations that may be important during a major disaster. Listening Post locations might include an Alternate Incident Command Post, BEECN sites, or Fire Stations. Each Listening Post should have a minimum of two participants.

Upon arrival, the Listening Post checks in with the Command Post and records the radio voice quality value for the conversation. The Listening Post then listens passively to and evaluates the Radio Voice Quality of Rover Team broadcasts for the duration of the Survey Session. The participants will collaborate to decide on a radio voice quality value.

Radio Voice Quality Values

Radio voice quality is rated on a six-point scale, from 5 for the "best" to 1 for the "worst" and 0 for no signal at all.

Intelligibility	Value	Color
No noise, full quieting. Broadcast/phone quality.	5	Dark green
Slight noise, fully readable.	4	Light green
Marginal voice communication. Occasional unintelligible words, noisy; weak audio level.	3	Yellow
Unreliable, difficult to copy, frequent repeats are needed.	2	Orange
Unintelligible, signal is barely evident.	1	Red
No audio signal is detectable.	0	Black

Radio Mapping Session: Process

The Radio Survey Session begins with participants gathering at the Radio Survey Command Post. Survey participants should check in using NET Form 2A Personnel Check In and provide mobile phone numbers on the form to provide a backup communication channel.

Listening Posts are provided with copies of the Radio Survey – Command/Listening Post Log form and the location of the Listening Post. Rover Teams are provided with copies of the Radio Survey – Rover Team Log form and the Survey Area Map for their assigned Survey Area.

It is good practice to assign Rover Team participants to parts of the NET Service Area with which they are less familiar. Rover Teams should examine the Survey Locations in their designated area to develop a travel plan. Generally, each Rover Team should start by reporting from locations nearest the Command Post and record results at each Survey Location while traveling away from the Command Post.

Expect that the SRO will be handling Rover Team messages at the rate of one message every two minutes or less.

Modifications to the Radio Coverage Survey Action Plan may be announced at this time.

Listening Post and Rover Team Dispatching

Listening Posts and Rover Teams must perform a radio check with the Command Post before leaving the Command Post area. This radio check ensures that radio equipment is operational and set to the correct channel. The radio channel used for the survey should be the channel specified in the NET Operations Plan.

Rover Teams and Listening Posts should be provided with the mobile phone number for the Command Post for backup communication.

Listening Posts should be dispatched first. Rover Teams should be dispatched after Listening Posts have been set up and checked in with the Command Post.

Each dispatch should be recorded by the Survey Team Leader using the NET Form 3 Team Leader Assignment Tracking Log.

End of Survey Session

Rover Teams should inform the Command Post when they have completed their survey and then return to the Command Post. The Command Post should recall the Listening Posts when all Rover Teams have reported the completion of their surveys.

The Command Post may terminate the survey at any time with a radio message to the Listening Posts and Rover Teams. At this time, Listening Posts and Rover Teams participants should return to the Command Post. If radio communication is lost, the Command Post may use backup mobile phone numbers to recall participants.

The return of each Listening Post and Rover Team should be recorded using the NET Form 3 Team Leader Assignment Tracking Log.

All participants should participate in a “Hot Wash” to share their experiences, what went well, and what could be improved.

Participants will check out at the end of the session using NET Form 2A Personnel Check In.

The Command Post Scribe is responsible for collecting all Rover Team Log and Command/Listening Post Log forms along with NET Form 2a and NET Form 3.

Processing Radio Mapping Data

Information collected during the Survey Session is recorded in a Radio Voice Quality Summary Spreadsheet and then plotted using My Google Maps to produce a NET Service Area FRS/GMRS Radio Voice Quality Map.

Radio Voice Quality Summary Spreadsheet

Information from the Log forms used by the Command Post, Listening Posts, and Rover Teams should be transferred to a Summary Spreadsheet before being plotted using My Google Maps. The spreadsheet should include these columns:

• Time – Use military time, (24 hour clock),
• Rover Team Name,
• Survey Location – street intersection, address, or landmark place name,
• Command Post Voice Quality Value – as heard by the Command Post,
• Rover Team Voice Quality Value – as heard by the Rover Team, and
• Listening Post Voice Quality Value – as heard by the Listening Post. One column should be used for each Listening Post.

Organizing this information into these columns permits the sorting of messages by time, team name, location, and Voice Quality Values. The Survey Location is entered into two columns, one for each street at the intersection.

Each row in the spreadsheet represents a report for a single Survey Location. Compare the recorded times and Rover Team Survey Locations to correlate reports across Log forms.

Set the background color of each cell to reflect the Voice Quality Value recorded in that cell.

Each Survey Session should be recorded in a separate spreadsheet or tab in a single spreadsheet. A sample spreadsheet is located here. (add full URL as well as hyperlink)

Radio Voice Quality Map Plotting

Create separate NET Service Area FRS/GMRS Radio Voice Quality Maps for the Command Post and each Listening Post. A guide to using My Google Maps to plot Radio Coverage Survey information is located here. (add full URL as well as hyperlink)

Voice quality markers

Add Voice Quality Markers to each map at each Survey Location. Set the color of each marker to reflect the reported Voice Quality Value reported for that Survey Location. If the Command Post or Listening Post and Rover Team report different Voice Quality Values for the same message, use the lower value. Just as a chain is only as strong as its weakest link, the quality of a conversation can be considered to be only as strong as its weakest message direction.

After all Voice Quality Markers have been added, use a Shape to enclose adjacent markers that share the same color. The Shape color should match the color of the enclosed Markers.

Other markers

Other markers may be added to each map to indicate locations for:

• NET Primary Incident Command Post,
• NET Alternate Incident Command Post,
• Listening Posts - BEECN sites, Fire Stations, etc.
• Community Resiliency Pod Assembly Areas, and
• Other satellite locations.

The shape and color of these markers should be chosen to distinguish them from Voice Quality Markers and from each other by type. For example, all BEECN markers should share the same shape and color but differ from all other markers.

Radio Voice Quality Map Publishing

The NET Service Area FRS/GMRS Radio Voice Quality Maps may be published in large-scale and notebook-size formats.

Large-scale printed maps could be used in the Incident Command Post by the Incident Command Leader, Amateur Radio Operator, Neighborhood Radio Operator and their Scribes.

Notebook-size maps may be printed in 8-1/2” by 11” format for use by deployed Strike Teams. The Strike Teams may use these maps to identify locations where they can more likely establish communications with the Incident Command Post.

Additional Radio Coverage Survey Sessions

Additional Survey Sessions may be used to fill in gaps, perform spot checks, or to identify any changes in Radio Voice Quality due to variables that include:

• Radio Type – the difference between FRS and GMRS radios,
• Vegetation Density – changes in the amount of tree foliage, and
• Obstructions – Construction or removal of structures that may affect signal propagation.