The fingerprinting process is the most important step during the deployment of Accuware Indoor Navigation, Accuware Indoor Tracking and Accuware Wearabouts. Even if it is an easy process (that has to be performed just once), it can be also time-consuming and this is why it needs to be performed carefully and evaluated step by step while being done. The goal of ambient signals-based location technology is to exploit differences across the site, uniquely “labeling” each physical location with the list of radio signal sources detected along with their observed signal strengths (RSS). Locating mobile devices then becomes a matter of comparing the real-time radio signals detected against the radio signals detected during the fingerprinting phase in specific locations. Therefore, assessing fingerprinting quality requires examining the fingerprints data collected to ensure that measurable differences were recorded across the site.

In this support page you will find a description of all the items that need to be checked during the evaluation of the fingerprinting process.

 

PLEASE READ: the evaluation of the fingerprints must be done using the tools available under the Fingerprinting section of the Accuware dashboard. Before proceeding you must have read a description of all the elements and tools available inside the Fingerprinting section:

1 – Evaluation of the radio fingerprints

1.1 – Spacing between the fingerprints

The accuracy provided by the Accuware engine is a function of the amount of fingerprints collected during the fingerprinting phase. For this reason, you need to varify that the spacing between the fingerprints is not greater than 2 meters otherwise the results could be negatively affected. If the spacing between the fingerprints is greater than 2 meters, the reason could be:

  • the device used for the fingerprinting – mobile devices have different scanning rates. Some devices with the 5 GHz Wi-Fi radio active collect the fingerprints with a lower rate, which results in a higher spacing between the fingerprints. By disabling the 5 GHz radio you should be able to collect the fingerprints with an higher rate (resulting in a smaller distance between the fingerprints). This can be done from the Advanced settings of Android (Settings > Wi-Fi > Advanced > Wi-Fi frequency band > 2.4 GHz only). After this step, you need to delete the fingerprints for the entire site and perform the fingerprinting process from scratchSometime it is not possible to disable the 5 GHz radio because a limitation of the Android device, or because you are interested in collecting the radio signals from WiFi access points working on 5 GHz. In this case, to ensure the collection of an adequate number of fingerprints, you should follow one of these workarounds (in order of preference):
    1. use another (older) Android device with the option to disable the 5 GHz radio.
    2. walk more slowly during the collection of the fingerprints.
    3. collect the fingerprints on the same route more than once.
  • the walking speed – if you walk fast during the fingerprinting process the spacing between the fingerprints will be higher. By walking at a regular speed you will be able to reduce the spacing between the fingerprints, increasing thus the accuracy.
  • (only for iBeacons) the transmission rate of the radio signal sources – if the radio signal sources transmit their identifiers with a low rate, then there could be gaps between the fingerprints. If you can change the transmission frequency/advertisement rate of the signal sources, we strongly invite you to do this. You need to be sure that all the radio signals are transmitting their identifiers with a rate that is not lower than 1 transmission/secondAfter this step, you need to delete the fingerprints for the entire site and perform the fingerprinting process from scratch.

The fingerprinting in the image below is affected by this problem – about 5 meters between each fingerprint!
(you can use as a reference measure the Google Map ruler highlighted in red in the bottom part of the image)

1.2 – Overall variability of the radio signals

The accuracy provided by the Accuware engine is a function of the overall variability of the radio signals detected during the fingerprinting phase. The overall variability can be checked by enabling the check box Max RSS value. By checking that check box you can see a heat map of fingerprints where the color of each fingerprint is a function of the highest RSS value detected among all the radio signal sources. Looking at the heat map you have to verify that there are no areas with cold colors (blue). If there are areas with cold colors, the reasons could be:

  • there are only iBeacons installed – in this case it is completely normal that the color of the fingerprints is colder (compared to the color of the fingerprints related to WiFi access points) and you don’t have to be worried. The reason is due to the fact that the transmission power of the iBeacons is lower compared to the the transmission power of WiFi access points.
  • the transmission power of the radio signal sources – if you are sure that in those areas there are radio signals, then the cold colors are due to the fact that the radio signals are not transmitting at their maximum transmission power. Sometime there is nothing to do about this because you don’t have the freedom to change the transmission power of the radio signal sources. If you have the freedom to change the parameters of the radio signal sources then you have to:
    • set the the radio signal source at its maximum transmission power.
    • delete the fingerprints for the entire site and perform the fingerprinting process from scratch.
  • the absence of radio signal sources – if in those areas there are no radio signals, then you need to:
    • install additional radio signals.
    • delete the fingerprints for the entire site and perform the fingerprinting process from scratch.

The red area in the image below is affected by this problem
(despite this, in general the one below can be considered a quite good fingerprinting)

1.3 – Variability of each radio signal

The accuracy provided by the Accuware engine is a function of the contribution given by all the radio signals deployed in the area. This is why it is always good to verify these things:

Verify the heat map of the fingerprints for (at least) the first 10 radio signals with the highest amount of Points

By sorting the table by Points and then clicking on the Show button next to each one of the first 10 radio signals you have to verify that:

  • the fingerprints for each radio signal source vary in strength (from colder colors to warm colors) along a trained route – basically by looking at the fingerprints for each radio signal, you would have to be able to estimate the location of the radio signal by looking at the color of the fingerprints (the radio signal source is located in the area with warmer colors). Signal strength differences are essential for ensuring that multiple locations along a route can be told apart.
    • If the site is made of 1 level and the fingerprints for a specific radio signal source are never warm, then the reason could be:
      • the location of the radio signal source – it could be that the radio signal source is far away. Sometimes there is nothing to do about this because you don’t have the freedom to change the locations of the radio signal sources. Anyway this is not a big problem if there are other radio signal sources that have been detected with an high RSS inside the same area. If you have the freedom to move the radio signal sources then you have to:
        • move the radio signal source into another location in order to give a positive contribution to the location.
        • delete the fingerprints for the entire site and perform the fingerprinting process from scratch.
      • the transmission power of the radio signal – if you are sure about the fact that the radio signal source is not far away, then it means that the radio signal source is not set to transmit at its maximum power. Sometime there is nothing to do about this because you don’t have the freedom to change the transmission power of the radio signal sources. Anyway this is not a big problem if there are other radio signal sources that have been detected with an high RSS inside the same area. If you have the freedom to change the parameters of the radio signal sources then you have to:
        • set the radio signal source at its maximum transmission power.
        • delete the fingerprints for the entire site and perform the fingerprinting process from scratch.
    • If the site is made of multiple levels and the fingerprints for a specific radio signal source are never warm on a level, then the reasons could be:
      • the radio signal is physically located on another level – please check if the fingerprints for that specific radio signal are warm at least on the level above or below. If the fingerprints for that specific radio signal are not warm on any of the levels then it means that the radio signal is not transmitting at its maximum transmission power. Sometime there is nothing to do about this because you don’t have the freedom to change the transmission power of the radio signal sources. Anyway this is not a big problem if there are other radio signal sources that have been detected with an high RSS inside the same area. If you have the freedom to change the parameters of the radio signal sources then you have to:
        • set the radio signal source at its maximum transmission power.
        • delete the fingerprints for the entire site and perform the fingerprinting process from scratch.

The red area in the image below is the only area in which the radio signal source 06181A31B996 has been detected during the fingerprinting process

  • the fingerprints for each radio signal source vary uniformely (from colder colors to warm colors) along a trained route -if there is not a uniform variation of the fingerprints colors and there are some fingerprints with cold colors (blue) among other fingerprints with warm colors, then the problem is related to the Bluetooth/Wi-Fi drivers of your Android device. You can solve this in one of the following ways:
    1. delete the fingerprints for the entire site and disable the Wi-Fi scanning (if you need to collect the fingerprints of iBeacons) following these steps:
      • access the Settings of the Accuware Indoors App and set Beacon Mode to iBeacons only
      • disable the WiFi chip on your device (doing this you will have to use a cellular data connection to upload the fingerprints!)
      • access the Settings of Android and disable the switch Scanning Always Available under the Advanced Setting of the Wi-Fi
    2. delete the fingerprints for the entire site and disable the Bluetooth scanning (if you need to collect the fingerprints of Wi-Fi access points) following these steps:
      • access the Settings of the Accuware Indoors App and setting the Beacon Mode to Wi-Fi only
      • disable the Bluetooth chip on your device
    3. if you are not able to solve with the 2 methods above then:
      • delete the fingerprints for the entire site and use another Android device to perform the fingerprinting process (if you have the possibility to do so).
      • delete the fingerprints for the entire site and use an iOS device to perform the fingerprinting process (if you have the possibility to do so and if you need to detect ONLY iBeacons).

In the red area in the image below there is not a uniform variation of the fingerprints colors.
There are some fingerprints with cold colors (blue) among other fingerprints with warm colors (red)

Verify the heat map of the fingerprints for (at least) the first 5 radio signals with the highest value of Max

By sorting the table by Max and then clicking on the Show button you have to verify that the first 5 radio signal sources do not have Max values equal to 0. Max values equal to 0 can have a negative influence on the accuracy. These RSS readings equal to 0 dBm could be related to the fact that:

  • you are carrying a mobile hotspot with you. In this case you need to:
    • delete the fingerprints for the entire site and turn off the mobile hotspot and perform the fingerprinting process from scratch.
  • something is wrong with the device that you are using for the fingerprinting process (please submit a support request using this form and let us know the device used for the fingerprinting process). In this case you need to:
    • delete the fingerprints for the entire site and use another Android device to perform the fingerprinting process (if you have the possibility to do so).

1.4 – Area covered during the fingerprinting process

The accuracy provided by the Accuware engine is a function of the area covered by the fingerprints. The fingerprints MUST be present on all the routes where the Accuware engine will be used (all the paths where people will be found on). If you realize that a specific area is not covered, you have to perform the fingerprinting in that specific area (on that specific path).

The red areas in the image do not contain fingerprints and the accuracy will not be good if Wearabouts or Accuware Indoor will be used in those areas

1.5 – Amount of radio signals

The accuracy provided by the Accuware engine is also a function of the amount of radio signals detected during the fingerprinting phase. There is no unique and standard equation to compute the perfect number of radio signals for each environment and there is no limit regarding the maximum number. Increasing the radio signals density will always increase the system accuracy.

Once the fingerprinting is complete, and assuming that the radio signals are displaced uniformly in a grid pattern inside the environment, using the NUMBER OF RADIO SIGNALS reported inside the Show aggregated metrics of the Accuware fingerprints dashboard and knowing the AREA of your site, you can calculate the average RADIO SIGNAL SPACING and evaluate if the spacing is small enough to allow you to reach a desired  AVERAGE ACCURACY:

    \[Radio Signal Spacing = \frac{\sqrt{Area}}{\sqrt{Radio Signals}-1}\]

Here is a rough estimate of how the level of accuracy varies with the RADIO SIGNALS SPACING:

~12 meters of RADIO SIGNALS SPACING -> leads an AVERAGE ACCURACY of ~1 meter 
~18 meters of RADIO SIGNALS SPACING -> leads an AVERAGE ACCURACY of ~2 meters

2 – Evaluation of the camera fingerprints

Soon available