Filter Command
A window allowing the user to set various filtering parameters will appear when this option is selected. To edit a targets filter parameters select the target number from the target number list box using the mouse or the arrow keys. The current filter parameters for that target will be displayed in the filter window controls. Change the filter parameters to the desired settings. To set the new filter parameters click the Apply button or the Ok button. The Ok button will save the filter settings for that parameter and exit the program. The Apply button will save the filter settings for that parameter but not exit the program. To set the filter parameters for more than one target at once, you must select the target number using the list box, change the desired settings and click Apply for each target.
Note: The Max Range, Min Depth and Max Depth settings are the same for each target. For example, changing the Max Range, Min Depth and Max Depth filter parameters for target number 1 will change the Max Range, Min Depth and Max Depth to the new settings for all targets.
Please note the Alpha Beta and On Site filters may not be used at the same time. However either Alpha Beta or On Site may be used with the Velocity filter. In addition Alpha Beta, On Site and Velocity may not be set to on (checked) when Raw is selected. If the Raw check box is clicked, the Alpha Beta, On Site and Velocity filters will be automatically set to off. If the Alpha Beta filter is selected, both the On Site filter and Raw or will automatically set to off. If the On Site filter is selected, both the Alpha Beta filter and Raw or will automatically set to off. However the Max Depth, Min Depth and Max Range filters may be used when Raw or any of the other filters are selected.
IPS Target:
allows the user to select which of nine possible targets the filter data will be applied to. The type of filter used for a target will be displayed after the target name in the target position box in the lower right hand corner of the screen. For example if raw data is being used for target number one Fish, then only Fish will be displayed as the target name in the target position box. If the velocity filter and on-site filter are set to on then Fish FVO will be displayed as the target name. If the target name exceeds 16 characters then the last 4 characters of the target name will be truncated to make room for the filter information if necessary. The Max-Range, Min-Depth and Max-Depth settings will not appear after the target name as they are not specific for each target. For more information see the Target Position Box section of this manual.
System Units:
displays the current system units. This setting cannot be changed from this dialog box. To set system units select Display Settings from the View Menu and select the appropriate units under the Display Units option.
Raw Data:
all useful BATS data is saved without any IPS software filtering at a rate determined by the output rate of the instrument used to track the target(s) or ship. See the section File Save Command in the FILE MENU portion of the IPS help for further information. The data is displayed in the target information box in the lower right portion of the screen. If the most recently acquired data point is fully acceptable the highlighted portion in the box reads "OK". Otherwise the most recently acquired data point has been rejected or is questionable. In this case an error or warning message corresponding to an BATS error code or warning message will be displayed in the highlighted portion of the target information box. Only the Max Range, Min Depth and Max Depth are available if Raw Data has been selected.
Velocity:
the total linear distance between the last accepted data position and the newly acquired data point is calculated. If the current position is unreasonable based on the maximum target velocity entered and time between acquiring of the data points the new data point will be discarded. The error message "Geo Vel" will also be displayed in the target information box. Use of this filter is appropriate at all times. Allowing the IPS software to control velocity filtering instead of the BATS is advantageous because the IPS calculates the total linear distance between the data points using the geodetic positions of the target. The BATS calculates the velocity between two points based on the relative heading of the ship. Therefore a rapid change in the heading of the ship could cause a valid data point to be rejected. If a data point is rejected by the BATS system error code 5 "excessive target velocity" will be displayed in the dialog box. The IPS software also allows adjustment of the maximum velocity of the target used in velocity filtering. Select Velocity and enter the maximum velocity in the edit box provided next to the Velocity option. The minimum maximum target velocity allowed is 0.25 knots. The largest maximum target velocity allowable and the default maximum velocity are both 10 knots. When using the BATS for velocity filtering the maximum target velocity used is nominally 4.5m/sec (8.7 knots).
Alpha-Beta:
filter is equivalent to a first order Kalman filter. The range and bearing values from the BATS system are processed for an improved estimate of the range, bearing and velocity of the target relative to the surface support ship. This filter is best used to track an active target moving in a predictably. For example for a target moving in a preprogrammed manner at a relatively slow speed such as an side scan sonar the Alpha Beta filter could be set at 80% or higher. For a target moving in a less predictable manner and a higher rate of speed such as ROV the Alpha Beta filter should be set to less than 80%. Enter the desired Alpha Beta percent in the edit box provided next to the Alpha Beta option. The minimum percentage that may be entered is 0 the maximum number of seconds is 99. The default value is 50.
On-Site:
the filtering of the positional data acquired for a submerged target is done in order to improve the displayed positions. By rejecting any data point(s) that are statistically different from the majority of the data points collected in the user selected period, based upon a Chi square distribution with two degrees of freedom (df=2). On Site filtering should be used if the target is known to be at one location ==> "on-site". Enter the number of seconds for the selected period in the edit box provided next to the On Site option. The minimum number of seconds that may be entered is 2 the maximum number of seconds is 60. The default value is 20.
The filtering model utilized, for the improvement of a submerged target's display is based upon the following conditions: 1) The latitudes and longitudes are normally distributed about the mean latitude and mean longitude. 2) The existence of independence; the squares of distances are Chi Square distributed. Once the data has be filtered the individual data points are then reduced using a "Maximum-Likelihood" estimation. This process calculates weighting factors for each data point to give more influence to data points that are closer to the mean latitude and longitude.
DVL Aided:
if enabled (checked) and if real time DVL data is coming in the DVL course and speed over ground data will be used to remove scatter in the USBL data. Not implemented at this time.
Depth Offset:
allows the user to enter the Depth Offset used in filtering. The Depth Offset must be between 32.81 feet and -32.81 feet (10.00 to -10.00) meters. The default is 0.00.
Depth Scale Factor:
allows the user to enter the Depth Scale Factor used in filtering. The Depth Scale Factor must be between 10.00 to -10.00. The default is 0.0000.
Max Range:
the maximum range the target can be from the surface support vessel. Any BATS data received that has the x, y, or Horizontal range greater than Max Range is rejected. The minimum range allowed is 0 feet. The maximum range allowed and the default value are both 13120 feet (4000 m). Enter the maximum range in the edit box provided.
Min Depth:
the minimum depth that will be accepted from the BATS system. If the depth from the current reading is less than the Min Depth setting in the IPS software the reading is rejected. The minimum depth allowed and the default value are both 0 feet. The maximum Minimum Depth allowed is 10000 feet (3048 m). Enter the Minimum Depth in the edit box provided.
Max Depth:
the maximum depth that will be accepted from either the BATS system. The maximum depth that may be entered and the default value are both 10000 feet (3048 m). The minimum depth is 0 feet. Enter the Maximum Depth in the edit box provided.