Vemco VR100 - Detection Parameter Settings

VEMCO – VR100 Manual 28 May 2018 69
The accuracy of GPS fixes can be improved by a Satellite Based Augmentation System (SBAS), which is
only available is certain areas of the world. The VR100-200 hardware version supports these SBAS services,
depending on your geographic location:
 WAAS (North America)
 EGNOS (Europe)
 MSAS (Japan)
The VR100 will utilize SBAS if the signal is detected, and this will be indicated by displaying “SBAS” on the
third line of the main menu screen.
This feature is not supported by the VR100-100 hardware version.
6.9 Detection Parameters
The detection parameter levels are used to determine how a real signal, referred to as a detection, is
distinguished from background noise. The VR100 constantly receives a signal similar to the one shown in the
drawing below. This usually includes a large amount of background noise from sources such as noises in the
hydrophone’s environment, electronic components in the receiver, etc. A “cut-off” level must be selected to
decide what a genuine detection is and what a spike in the background noise is. A spike in the background
noise that is mistakenly identified as a detection is called a “false-detection”. The VR100 allows the user to
select one of three levels to be used to determine what is considered a genuine detection. These levels are
Near, Norm, and Far.
1. NEAR: This is the “safest” detection level because it rejects anything that could be noise, nearly
eliminating false-detections. Unfortunately, it may reject fainter signals that are real. In the sketch
below, everything over the “Near” line is considered a genuine detection. In this case, only one
signal (the first one) was accepted. The other four signals were incorrectly considered to be
background noise and weren’t included. Use the “Near” level when the “Norm” level is receiving too
many echoes. This can happen when the tags are in an enclosed area like a tank.
NOTE: This example has been exaggerated for illustration purposes. In most cases there
will be no false detections with Near or Norm, and very few with Far.