Location Based Scanning

From The RadioReference Wiki


Location-based scanning is a patented function of certain Uniden DMA scanners. (US Patents 6,192,233 and 9,941,120.)

According to Uniden, location-based scanning allows you to control which systems/sites and channel groups are scanned based on your exact location. This frees you from having to manually enable and disable systems or channel groups as you change location. Specifically, location-based scanning uses the scanners lockout function to control what is scanned based on your location. It unlocks systems, sites, or channel groups when you are inside an element's radius. When you exit the radius, the element is temporarily locked out.

Uniden scanners BCD996T, BCT15, BCT15X, BCD996P2, BCD325P2 and all XT models (BC346XT, BCD396XT, BCD996XT) support location-based scanning. The Uniden HomePatrol-1, HomePatrol-2, BCD436HP, BCD536HP, SDS100 and SDS200 all support location-based scanning, with the added feature of ZIP Code control. These has the ability to let you set your location using a ZIP Code, but the code itself is not used rather it is converted to latitude and longitude.

The HP series scanners comes preloaded with the entire RadioReference database and users can enter a ZIP, a range in miles, and the types of services they want to hear. Within seconds users can be listening to all Police Dispatch calls within a 5 miles range of downtown Indianapolis, etc.

The scanners do not have a GPS receiver built-in, you must purchase an aftermarket GPS device compatible with your scanner. Details for connecting a GPS receiver vary by scanner. Compatible GPS devices all use the common DB9 serial type connection. For the mobile models (BCT15, BCD996T, BCT15X, BCD996XT) you can connect directly to the rear port of the scanner. For the portable scanners (BC346XT and BCD396XT) you can use the data cable that was supplied with the scanner. Some installations may require a gender changer to mate DB-9 connections. In the case of either portable scanner, if you use the cable that came with the scanner a null modem/gender changer is a requirement. A null modem adapter is not required if you purchase the optional GPS adapter cable designed for use with the HP-1 and other DMA scanners.

The GPS function of your scanner can be used for more than just controlling what you listen to. For example, you can enter, store and have the scanner alert you to dangerous intersections or when you are going too fast, etc. These are commonly referred to as location alert functions.

In addition to the basic GPS functions, for every entry you want to monitor with your scanner, you can program a set of criteria using GPS coordinates and a range. (In the case of the HP-1, this comes already pre-programmed or you can program any entity yourself.) To better understand how this works, you should become familiar with how to program your scanner with third party software. You can program manually, but it can be more difficult and time consuming. This article does not cover how to program entities (frequencies or systems) into your scanner, rather the concept and understanding of programming locations with an entity or alert function.

Understanding GPS data in the RadioReference database

In addition to being familiar with your scanner and an understanding of programming locations (described above) you should have a general understanding of where RadioReference stores location data with its radio data that can be downloaded by third party software.

While it is not necessary to know the specific names of all data fields, currently the RadioReference database stores location data in several database fields that are not used for Location-based scanning, such as: ZIP Code info and FCC location, etc. For example, when you review any agency info in the database if you click on the FCC license call sign the GPS coordinates registered with the FCC will sometimes be shown. This data is not what is used for location based scanning.

It is very helpful to be aware of the RadioReference database fields that match up to what can be used in the scanners. Each description below is followed by a sample link where RadioReference users can view specific types of data online in report format. The following fields correspond directly to the data used in the scanners.

Trunked System site – a trunking site can have specific location data assigned to it. If none is specified, then it inherits the location data based on the county that it is located in. If no county is defined for the site, the site inherits the trunked system default location data. The name of the field used by the third party software is called TrsSite

Trunked System Talkgroup category – a talkgroup category can have specific location data assigned to it. If none is specified, it inherits the trunked system default location data. The name of the field used by the third party software is called TalkgroupCat

Frequency Subcategory - a conventional frequency subcategory can have specific location data assigned to it. If no location data is specified for the frequency subcategory, then it inherits location data from the parent agency or county. The name of the field used by the third party software is called subcat

Related Wiki-Templates - To place any of the above links into an article, please use the corresponding Wiki-templates:


RadioReference members can submit data for any of these fields where there is none or where there are errors. (Remember, if you are submitting data, that the coordinates and range should be entered for the intended useable area, not the coverage area. For example, if Agency XYZ has a 300 watt repeater that you can hear for miles away from the city, the intended usable area is more likely to be the agency boundary of the city or county. When submitting data to the database you would enter the radius necessary to cover the city or county, not a larger radius to cover the capable listening area of the transmitter.) Users who desire to add Location_Based_Info should become very familiar with RR_Database_Submission_Guidelines before submitting changes to the RadioReference database.

The descriptions of the fields described above make reference to ‘inheriting’ data from higher levels of the database. There are multiple fields that the RadioReference User cannot see by looking at the database online. The key fields relevant to location-based scanning that you cannot see are as follows:

  1. State – a state can have location data assigned to it that serves as a default set of location data for the state or for state agencies.
  2. County – a county can have location data assigned to it that serves as a default set of location data for the county.
  3. Agency – an agency can have location data assigned to it that serves as a default set of location data for the agency.
  4. Trunk System – a trunked system can have location data assigned to it that serves as a default set of location data for the entire system.

The RadioReference database does not currently show the RR user GPS data for State, County, Agency, or System in any of the online user reports. For example, if you were to review the online report for any conventional frequency subcategory data, if there is no data entered for that subcategory you will see absolutely no data (inherited data is not shown online.) All data values are processed and provided to third party applications using the RadioReference Web Service API with an indication if it is an inherited or native value. The inherit feature/function will appear to the end user as if it can only be seen by third party applications.

The RadioReference database is by no means complete, but it has the capability to store all of the info necessary for Location-based Scanning. You can cut and paste the info from the database for free, but to download this information directly into your scanner you will need a third party software that is capable of connecting to RadioReference and you will need a paid subscription to website for access.

Using third party software with the GPS features

Most importantly you will simply want to understand the capabilities of the scanners ability to store GPS data compared to the fields that are used by the RadioReference Web Service to interface with third party software that connects to the database and extracts useable data.

For HP-1 users, it is not required to interface or access RadioReference directly. While you can download data and GPS coordinates, Uniden provides HP-1 owners with weekly updates for no charge via the Sentinel software. Uniden extracts data from RadioReference and tweaks it for the HP-1 radio. For all other scanners, some of the DMA supported applications are Location-Based scanning capable.

It is important to make sure the software you have selected uses the ‘inherit’ feature capability if you expect to download accurate GPS data. Each time RadioReference changes the structure of its database they release a set of code or instructions, Simple Object Access Protocol (SOAP), to third party vendors so they can utilize any new features. The “inherit” capabilities were released in version 8 of the SOAP RadioReference Web Service. The current release is version 9 and many third party software vendors are using release 9 or in the process of upgrading their programs to be compatible. If you are not sure, or you are downloading unexpected GPS data that doesn’t match what you expect or what is in the RadioReference database, ask the vendor of the software product you have selected.

Third party software using older versions of the Radio Reference Web Service can cause missing and/or erroneous location-based data to be downloaded. In addition, programs that are designed to program a variety of scanners may be misleading you as to where the data is being stored or used; it is possible that the program is downloading data in one location that would be used with XT models and data in another location that would be used with other models, etc. Without a good knowledge of the scanners and data explained above, even the experienced user can easily be confused.

The XT model scanners are capable of storing coordinates with each Trunked Radio Site within a system (this can be single site systems or multi-site systems) and within each set or “GROUP” of Talk Group ID’s (TGID) within a system. The XT models also can store coordinates for a set or “GROUP” of frequencies within a conventional system. The non-XT models handle coordinates differently and do not store GPS coordinates at the TGID level, you can only segment by trunk site. For the conventional entries on the non-XT models the GPS data is stored at the conventional system level, not the group level – which may or may not be the same depending on what you have programmed. In either cases data is retrieved from RadioReference the same for both scanner types. (For the Home Patrol, this is transparent to the user since it is translated to the Home Patrol database by Uniden on a weekly basis.)

Someday, ‘seamless’ GPS scanning may be a reality. For now, the data in the RadioReference database is only as good as what scanner enthusiasts populate into the database and the capabilities of the software/hardware using the data. The completeness of the database is evolving only as fast as users are adding data. To this accord, there may be cases where you want to enter your own data directly into the third party software before uploading to your scanner. However, where possible you should update the database if you can.

Most of the third party programs that handle location-based scanning have some sort of tools for viewing maps and searching locations necessary for programming locations. While the focus of this article has been how to understand the data that is downloaded from RadioReference automatically, there are some advantages to programming locations on your own.

Tips / Tricks for more effective location-based scanning

Not every city is the shape of a circle or is of moderate size. You may need to consider custom shapes and large listening areas when programming your scanner. As briefly suggested in the overview Wiki linked at the beginning of this page, you can create a duplicate site with a different radius to make an oblong entity. Essentially, the scanner narrows and expands the coverage area by scanning the same site twice (but it doesn’t slow the scan rotation enough to be noticeable to the end user since it only scans twice in overlap areas.) Your scanner also needs to be able to handle large geographical areas for statewide and nationwide channels in a scan rotation.

  1. A custom shaped listening area can be as simple as an oblong shape or it can accommodate the rare instance you may monitor a system that operates in two simulcast locations separated by a long distance. As a complex example, imagine a large military simulcast system with more than one base or campus. Your main listening area is base A & B & C (or however many campus locations.) Instead of drawing a large radius around the 3 campus locations you could create multiple sites for each location and have a radius for each that only covers the specific campus. If the military police travel one or two miles down certain roads to get from point A to point B, you can create more sites with smaller radius that follow the roads, essentially giving you location-based scanning coverage of just the areas in which the military police operate, the 3 main campuses and the roads in between.
  2. Statewide systems, depending on your state, may need to have custom shapes defined. GPS data for states in the radio reference database are all based on a perfect circle surrounding an entire state. In rare cases for statewide agencies listed in the database the agency may inherit the statewide coordinates if there are no agency, county, or subcategory coordinates entered in the database. However, you must be aware that the XT model scanners are only capable of storing a radius of up to 125 miles and the other models are only capable of up to 50 miles radius. If you live in an average or larger size state, you will likely encounter these limits. (Similarly, note that the third party software programs may round up or down and any radius under 1.0 may get rounded to 0 depending on the program you are using.) Hence, the data stored in the RadioReference database may not be useable in your scanner and may not be processed correctly by your third party software. In this case you can duplicate entries with different radius information to cover a large area – similar to the tip / trick above for odd shape sites.
  3. Nationwide frequencies listed in the RR are now able to be downloaded into many third party software programs. All of the Nationwide frequencies have a center point in the middle of the US and a range of 1800 miles. While the scanners have limitations on the range of a frequency, site or system, it would be memory prohibitive to draw many circles and enter duplicate entries for any Nationwide channels. You can always tell the software not to scan a particular entry using GPS. You will want to set all Nationwide frequencies to scan all the time, and you can manually lock them out if you need to. They will be active wherever you go (which is how scanning used to work anyhow, remember?)

In the future, both the RadioReference database and some scanners will also have the option of using multiple rectangles to define areas for a single entry, but for now using duplicate entries with different radiuses is the only way to create your own custom shaped listening area. (The HP-1 already can use rectangles, but no support is available in RadioReference yet.) As location-based scanning popularity grows, the number of users submitting changes and updates to the database will increase and the data will become more robust and accurate.

Location-based scanning can be as simple or complex as you want it to be. If you live in a major metropolitan area you can detail most Uniden scanners for your listening enjoyment to precisely where you are at any given moment. If you travel cross country you can attach GPS to your Uniden Home Patrol and drive from coast to coast without reprogramming and without missing the local action along the way.

Additional References

Easier to Read Manuals