Mobile InterferenceHunter Help : Using the MIH : Setting the Sensitivity
Setting the Sensitivity
Sensitivity relates to how data is collected in different types of geographical areas. In urban areas, small fluctuations in the receive power are more likely to be caused by a reflected or attenuated signal. We do not use these fluctuations in the location algorithm, so we lower the sensitivity by smoothing the data set. In rural areas there are fewer obstacles, so small changes in the receive power are more likely to be of interest. We use higher sensitivity (less smoothing) so these small changes can help locate the interference source.
In urban canyon settings, the GPS signal can suffer from multi-path and a stopped vehicle can appear to wonder some distance from its true location. Decreasing sensitivity in urban areas increases the minimum distance the vehicle’s position must change to be considered moving. In the case of 0, No Sensitivity (zero averaging), the data displayed will be raw data taken. No averaging has been applied to the data collected. Select the environment type that closely resembles the area that an interferer is being hunted.
Along with the Sensitivity settings there is a Peak Detection Threshold setting. Before a location estimate is made, it is important to have enough useful data that an estimate is of value. The algorithm requires a peak in power to be detected, indicating that you have driven somewhere in the neighborhood of the interference source.
If the threshold (power above background) for this peak is too low you will get false positives, meaning a location estimate based on multi-path or other environmental effect, rather than the true interferer location. When seeking low power sources, it is sometimes necessary to lower the peak detect threshold in order to get a position estimate at all. Generally, it is best to start with the Peak Detect Threshold set to High, and only lower it if you feel certain you are in the right area, but still not seeing a location estimate.
Both the Sensitivity and Peak Detect Threshold affect calculations over the entire data set each time a new value is added. The raw power levels are kept in memory. Therefore, changing settings during a hunt is perfectly fine. The new value will be applied to the entire data set, and changes are reversible.
1. Press to list the six selections.
2. Click on the selection that closely resembles the area you are hunting for an interferer or “0” to display only raw data taken.
3. Click Peak Detect Threshold and select High. If you are certain you are in the right area of the interferer but not seeing a location estimate, select Medium and if necessary Low.