There are two types of localization:
One way to do localization is to move to different locations one by one and to take bearings with the direction finder stationary at each location. This procedure is time-consuming but can be very accurate when the ideal fixed positions are selected. Such positions have a line of sight to the suspicious transmitter and are more or less equally distributed on a close circle around the suspicious transmitter, and there are no reflectors or obstacles close to the direction finder. Since the location of the suspicious transmitter is not known, it is difficult to select the direction finder positions in advance. Selection of the next location will often depend on the previous results.
The algorithm uses all the bearings stored in the Data Sets folder of the active working directory to calculate a localization heatmap. These bearings can be generated in two ways:
• By generating bearings via Level Meter, Horizontal Scan or Bearing measurements first and then starting a discrete localization based on these bearings.
• By starting a discrete localization in the Map view of the Auto DF task and then adding bearings to the active working directory.
1. Open the Level Meter or Horizontal Scan view in the RT Spectrum task, change settings as wanted.
2. Ensure you set the active working directory as needed (see here).
3. Press the Save key.
A data set with all settings and measurement results of the task is stored to the Data Sets folder of the active working directory.
4. Open an existing Auto DF task with the Map view or create a new one (see here).
5. In Map Mode select Disc. Localization.
6. Ensure you have selected the active working directory where you have stored your bearings before and change additional settings if needed.
7. Tap Start Localization.
Based on the stored data sets the localization is calculated.
8. If wanted. add additional bearings by tapping Add New Bearing.
These added bearings are immediately included in a recalculated localization.
9. Tap Save Localization to save the current localization or tap Stop and Save Localization to save the localization and to stop localization.
The localization results are stored as a data set in the Data Sets tap of the Data Logger.
1. Ensure the Data Sets tab in your current active working directory is empty or create a new active working directory (see here).
2. Open an existing Auto DF task with the Map view or create a new one (see here).
3. In Map Mode select Disc. Localization.
4. Tap Start Localization.
5. Tap the Add New Bearing button to add a bearing
Each bearing added is immediately included in a recalculated localization.
6. Tap Save Localization to save the current localization or tap Stop and Save Localization to save the localization and to stop localization.
The localization results are stored as a data set in the Data Sets tap of the Data Logger.
Another approach is to take the bearings while the direction finder is mounted on a moving vehicle. The advantage of this method is that bearings can be collected from many positions within a short time span. The disadvantage is that it is very likely that most of the bearings will be more or less random because they are taken from positions without line of sight. The localization algorithm SignalShark uses also work reliably even under such conditions. This localization method is often referred to as homing-in.
Continuous localization automatically takes bearings over time, stores them in a predefined record set and updates the heat map and the localization result accordingly.
In most cases, the heat map at the start of a homing-in drive in an urban environment will not show any useful information. This is because the localization algorithm needs line of sight situation bearings from a sufficient number of significantly different locations of the direction finder. It is therefore important to keep moving and scan the complete area where the suspicious transmitter might be located.
The useful bearings will intersect at a point close to the position of the suspicious transmitter, while the random bearings will intersect at random positions. It therefore makes sense after driving around the area for some time to drive then into the direction of the current hot spot and then drive around the hot spot area and observe the changes in the heat map.
The transmitter has probably been located if the red area on the heat map is reducing in size and its center is not moving significantly. In most cases, the estimated transmitter location will anyway converge on the true transmitter location as the drive time gets longer.
There are situations however where this is not the case:
• Dominant reflectors are present that have more line of sight situations than the transmitter.
• Other transmitters that use the same part of the spectrum as the suspicious transmitter are present close to the search area.
The bearing data itself does not give a hard criterion that could be used to decide whether the suspicious transmitter has been localized or not. The user must therefore decide when to end the homing-in drive. This decision can be aided by checking the plausibility of the estimated location of the suspicious transmitter.
For example, if the transmitter antenna can be seen then the homing-in process can be ended. If the situation is unclear, it can make sense to pause the drive in the vicinity of the estimated location and inspect this area visually or with handheld DF equipment. If the result of this inspection is negative, the homing-in drive can be resumed in areas that have not yet been visited.
1. Ensure you set the working directory as needed (see here).
2. Open an existing Auto DF task with the Map view or create a new one (see here).
3. In Map Mode select Cont. Localization.
4. Tap Start Localization.
5. Tap Save Localization to save the current localization or tap Stop and Save Localization to save the localization and to stop localization.
The localization results are stored as a data set in the Data Sets tap of the Data Logger.
1. Select
the working directory where your existing continuous localization records
are located.
They are stored in the Records
tap, not in the Data Sets
tab!
2. Open an existing Auto DF task with the Map view or create a new one (see here).
3. In Map Mode select Cont. Localization.
4. Tap the Select Record button and select a record from the dropdown list.
5. If needed select another Ftune in the Map view menu.
6. Tap Start Localization.
The localization is recalculated. Depending on the amount of stored data this may need some time.
7. If you want to add further bearings, tap
the Record Bearings
button.
If not, you can just save the recalculated localization.
8. Tap Save Localization to save the current localization or tap Stop and Save Localization to save the localization and to stop localization.
When a localization is based on a selected bearing record the added bearings are not written in a new created bearing records file but in the selected file.
The localization results are stored as a data set in the Data Sets tap of the Data Logger.
It is also recommended to create a screenshot of the measurement for easy exchange of localization results.