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974-72007001/1.0 1007D

Altimeter Operators Manual

Page

38 1007D

Altimeter

Altitude Detection Algorithm

Kongsberg Mesotech Ltd.

Port Coquitlam, BC - Canada

APPENDIX - 1007D ALTIMETER ALTITUDE

DETECTION ALGORITHM

The 1007D is a digital altimeter used in several applications such as bottom profiling
and forward-looking obstacle avoidance deployments. This appendix describes the
methods used to determine the altitude/return values from the sampled sonar data.

The following figure shows a typical altimeter return signal:

Min . Width Setting

Min. Gap Setting

Min

. Range

Setting

Min. Width Setting

Threshold

Setting

Time

ALTIMETER RETURN

Содержание 1007D

Страница 1: ...Kongsberg Maritime Operator manual 1007D Altimeter series ...

Страница 2: ......

Страница 3: ...974 72007001 1 0 1007D Altimeter Series Operators manual ...

Страница 4: ...ct to change without prior notice Kongsberg Mesotech Ltd shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing performance or use of this document 2008 Kongsberg Mesotech Ltd All rights reserved No part of this work covered by the copyright hereon may be reproduced or otherwise copied without prior permission from Kongsberg Mes...

Страница 5: ... 1 MOUNTING POSITION 13 3 2 ELECTRICAL CONNECTION 14 3 3 SYSTEM CHECKOUT 16 3 4 DEPLOYMENT 17 3 5 MAINTENANCE 17 4 TELEMETRY 18 4 1 808 MODE MESSAGES 19 4 1 1 Uplink Messages 19 4 1 2 Downlink Messages 20 4 2 809 MODE MESSAGES 21 4 2 1 Uplink Messages 21 4 2 2 Downlink Messages 22 5 OPTIONS 32 5 1 HARDWARE HOLD OFF 32 5 2 EXTERNAL SYNCHRONIZATION 32 5 3 AUXILIARY SERIAL OUTPUT 33 5 4 ANALOG OUTPUT...

Страница 6: ...974 72007001 1 0 1007D Altimeter Operators Manual VI This page is left intentionally blank ...

Страница 7: ...urable settings for operating parameters range resolution firing rate pulse width etc Configurable settings for detection parameters threshold range return pulse width etc First or peak level return based obstacle bottom detection Adjustable threshold based range measurements User selectable range windowing control RS485 or RS232 serial interface standard 3 basic models available standalone analog...

Страница 8: ...ended for remote operation where its output will be connected to a remote PC or MS1000 host or to other instrumentation such as a data acquisition system or a telemetry system Consequently the 1007D does not have any operating controls nor does it have a display The 1007D s processing features flexibility and performance are designed to address the requirements of many applications and deployment ...

Страница 9: ...y to the host computer in a number of selectable ASCII formats and range units Legacy Model 808 or 809 Altimeter output formats are also available Range measurements can also be output to a DC voltmeter from an optional analog interface like that found in our Model 807 Altimeters The voltage output is directly proportional to the range 10 volts corresponding to maximum range The 1007D s programmab...

Страница 10: ...ows several 1071 1171 scanning sonars and 1007D altimeters to be operated and synchronized with a single ethernet cable connection The MS1000 software displays altitude measurements in a directly readable format in a moveable display window An analog scope graph window provides the operator with a visual indication of the aggregate acoustic signal received each ping plotted as graph of signal stre...

Страница 11: ...ected back to the transducer by each target at a delay time proportional to its distance and at a strength related to its size and reflectivity The signal received by the transducer consists of a series of pulses or returns corresponding to each insonified target and is amplified and conditioned by an adjustable gain receiver The receiver output is sampled digitized and stored in internal memory o...

Страница 12: ...ies those returns that meet the following adjustable criteria as potential candidates for the final range measurement a minimum amplitude threshold b minimum pulse width c minimum inter pulse gap width d minimum range e maximum range Adjustments are made to these settings to reduce the detection of spurious and or low reflectance targets The minimum range setting can also be adjusted to eliminate ...

Страница 13: ... the sample data set then converted to a range estimate This estimate is then filtered using an adjustable range window that considers the new range estimate valid only if it is within a range window of the previous estimate This range window feature can be disabled if desired If after each ping a valid range estimate is determined the range data is either up linked as an ASCII string from the tel...

Страница 14: ...er requirements The 807 mode can only be entered as a power up default While operating in this mode the telemetry type RS232 RS485 or RS422 is fixed by a factory configured setting and cannot be changed b 808 mode emulates a standalone Model 808 Altimeter where range measurements are continuously output via a quasi full duplex telemetry interface RS232 RS485 or RS422 In this mode the altimeter acc...

Страница 15: ...S1000 compliant digital sector scanning sonar heads to be connected to a single cable The MS1000 mode can also entered from any of the standalone 807 808 or 809 modes if MS1000 telemetry is detected However this is possible only if the altimeter is configured for a telemetry type that agrees with that used by the MS1000 host PC Further details regarding 1007D setup and control with the MS1000 soft...

Страница 16: ...st the balance between ping rate and resolution as required In 809 mode this adjustment is performed by the Q command section 4 2 2 In MS1000 mode a slider adjustment in the MS1000 software controls the ping rate vs resolution optimization when profiling without a displayed image 2 3 Over range Condition An over range condition exists if a distinct valid return is not found within the altimeter s ...

Страница 17: ...ecting spurious mid water targets such as fish thereby improving tracking of hard sea bottoms In standalone 80x modes the offset is a constant value over the entire ping In MS1000 mode a menu selection of several TVG types is available as well as a user defined TVG configuration which allows custom settings for spreading loss absorption and overall gain 2 5 Auto GAIN Adjustment The 1007D s Auto Ga...

Страница 18: ...s where interfering mid water targets are present otherwise it should normally be disabled Moreover auto gain adjustment should only be enabled by operators with a complete understanding of the acoustics and the operating conditions in which the altimeter will be used It should not be used in obstacle avoidance applications When controlled by an MS1000 PC the auto gain adjustment is disabled ...

Страница 19: ...tion only and SHOULD NOT BE USED FOR MOUNTING When designing the mounting bracket be sure to allow enough room for installation and removal of the underwater connector 3 1 Mounting Position The 1007D altimeter is normally used to measure height above the sea floor and in this case must be mounted vertically with the transducer pointing down For special applications the altimeter can be mounted in ...

Страница 20: ...The standard telemetry configuration supports both RS485 and RS232 interface type specifications and is configured by the altimeter software In MS1000 mode the altimeter automatically detects configures the telemetry connection type to that used by the MS1000 host computer In standalone 80x mode the telemetry connection type will be set to a factory programmed default setting if an MS1000 host is ...

Страница 21: ...d according the factory configured settings for maximum range and maximum range output voltage specified when the altimeter is ordered For instance if the altimeter is configured to output 10V at 100m maximum range the range scale will be 10m volt In its most versatile configuration the 1007D altimeter with digital telemetry is controlled by a PC running MS1000 software The following figure shows ...

Страница 22: ...T of the water turn on the power supply and observe the following over range output time 0 0usec or empty range field received by the external PC For analog output the over range output level 0 05V should be measured by the DC voltmeter If possible confirm that supply current is between 150 and 450 milliamps 2 If all of the above appears normal the system should be tested in water of known depth w...

Страница 23: ...altimeter is designed to operate in depths up to 3000 meters To prevent improper operation and or damage to the unit protect the transducer face from contact with any surface or foreign object The 1007D s standard aluminum housing is anodized to prevent corrosion However for extended immersion in salt water it may be necessary to use sacrificial zinc anodes 3 5 Maintenance The only routine mainten...

Страница 24: ...te remain fixed until the unit is powered down If the altimeter is specifically configured in MS1000 mode only the standalone mode is not entered and the unit continues to search for an MS1000 host For special customer requirements an RS422 interface is available requiring the altimeter be fitted with a minimum 6 pin connector By definition the 808 and 809 digital communications are full duplex Th...

Страница 25: ...p link The serial communications settings for digital communications in all modes and protocols are 8 bits character 1 start bit 1 stop bit and no parity A standard default baud rate of 9600 bits second is programmed at the factory Consult the factory if a different default rate is required 4 1 808 Mode Messages This section outlines the uplink and downlink messages recognized in 808 mode 4 1 1 Up...

Страница 26: ...d to detect the start of the output data string When no valid reply has been detected or the depth is greater than the maximum range the value ddddd will be zero The line of characters is terminated by a carriage return line feed 4 1 2 Downlink Messages The following ASCII single character commands are recognized by the altimeter configured for 808 mode operation Ctrl S XOFF Pause Ctrl Q XON Resum...

Страница 27: ...tttttttlll CRLF range in microseconds SDDBT x x f x x M x x F hh CRLF range in NMEA format Depth Below Transducer only data for the current units selection will be output P CRLF Power on reset completed ready for command I CRLF Illegal command or parameter error command ignored X CRLF serial RX transmission error command ignored where f 1 4 indicating current maximum range setting rrrr range in 0 ...

Страница 28: ... zeros blank field indicates no return was received Only the range units currently selected will be filled Hh NMEA ASCII hex value of the 8 bit checksum of the exclusive OR of all characters after and before 4 2 2 Downlink Messages The following table of ASCII strings are recognized in 809 mode Those designated as new are not part of the original 809 telemetry specification and generate a CRLF ter...

Страница 29: ...N xxxx 0007 custom R0 minimum range in 10cm units xxxx 0000 5000 P x 4 xmit pulse width x 0 9 with pulse width x 1 50 s Q xxxxx 16000 maximum resolution in samples xxxxx 00238 16000 R x 2 maximum range x 1 20m 2 50m 3 100m 4 200m 0 custom R0 S x 0 NMEA o p scale x 0 meters 1 feet 2 fathoms T x 1 xmit gate x 0 listen only 1 XMIT1 2 XMIT2 3 XMIT1 XMIT2 4 FTX U xx or U xx 00 TVG fixed gain offset xx ...

Страница 30: ...mands listed in the table above in C Y For example the acknowledgment to the command string V is Vxxxx where xxxx is the current assumed sound velocity In some cases the current setting returned may be the actual setting used by the altimeter instead of the setting last issued by the host For instance the acknowledgment to the command string is string Q is Qxxxxx where xxxxx is the actual resoluti...

Страница 31: ...justed every shot according to the method selected by the Set Auto Gain Mode command D d Select Bottom Detection Method where d is one of 0 first return for obstacle avoidance applications 2 strongest return for bottom detection applications F f Select Range Output Format This command selects the format of the range output string where f is one of 0 legacy 809 format and scaling 1 NMEA Depth Below...

Страница 32: ...Threshold command m is one of 0 Disabled regardless of the Set Threshold command setting 1 Add or subtract a flat offset to shift the TVG curve up or down The performance and stability of the Auto Gain Adjustment is strongly dictated by Settings that affect the ping rate e g Set Range command Bottom Detection Method used Set Detection Method command Deployment conditions acoustic noise multipath t...

Страница 33: ...turn s at shorter range M xxxx Set Custom Maximum Range N xxxx Set Custom Minimum Range These commands set the range limits for the custom range setting R0 selected by the Set Range command where xxxx is a four character ASCII value with leading zeros as required representing the range in 10cm units The allowed minimum range setting is between 0003 and the current Custom Maximum Range setting The ...

Страница 34: ...lse length Q xxxxx Set Maximum Resolution This command sets the maximum resolution in samples in acquiring maximum range where xxxxx is a 5 ASCII digit with leading zeros as required value in 00238 16000 The altimeter will then attempt to sample the received acoustic signal at a rate Fs Fs Maximum Resolution in samples maximum range acoustic time At short ranges the actual resolution used may be l...

Страница 35: ...its set by the Set Custom Minimum Range and Set Custom Maximum Range commands For all range settings the altimeter attempts to assume the best resolution possible limited by the Set Maximum Resolution setting and hardware limits The actual resolution used can be determined by the Q QUERY command S x Select NMEA Units This command selects the units of the NMEA format range data where x is one of 0 ...

Страница 36: ... XMIT1 XMIT2 for factory test only 4 FTX for factory test only This command is for factory testing and must always be set to 1 for normal operation U xx or U xx Set TVG Gain Offset where xx 99 99 is the offset in 0 5dB units This command applies a fixed gain adjustment on the received signal to allow the operator to manually increase or decrease the gain It is effective in both the manual and auto...

Страница 37: ...d as a percentage of the Maximum Range setting Entering a value of 00 disables the range windowing feature X x Select Transmit Power where x is either 0 low or 1 high Y xxxx Set Minimum Ping Repetition Period where xxxx is 0050 9999 milliseconds The actual repetition rate will be a function of many of the other settings but will be no less than the setting issued by this command This setting is pa...

Страница 38: ...serted left floating or set to 5V Pinging will be paused while the hold off input is pulled down to zero volts However during this time the altimeter can still process incoming messages 5 2 External Synchronization In MS1000 mode this is a signal compatible with the MS1000 system synchronization method and can be used to connect to one or more MS1000 altimeters or scanning sonar heads in order to ...

Страница 39: ...ata format is identical to the factory configured default 809 format while operating in 807 808 or MS1000 modes In 809 mode the current 809 format will be used Consult the factory if a different interface type default baud rate or format is required This option also requires that a special connector be installed that provides extra connections for this interface 5 4 Analog Output An optional 807 t...

Страница 40: ...ating mode 807 808 mode maximum range is fixed to pre programmed default 809 mode maximum range is programmable MS1000 mode maximum range depends on display scale selected full scale output voltage corresponds to the selected range scale The analog output of the altimeter is capable of supplying up to 10 mA at 10 volts For maximum accuracy the load on the output should be kept as low as possible T...

Страница 41: ...surement and interfacing specifications The evaluation selection of various 807 mode configurations for standalone fixed range analog output applications ALTCONFIG will only work on 1007D altimeters that have digital telemetry interfaces i e analog output only configurations cannot be used with ALTCONFIG Settings are either menu selectable or chosen from among a collection of default settings stor...

Страница 42: ...ion s deployment geometry and water conditions then applying judicious modifications to the deployment strategy and or to the altimeter settings While a diagnosis of all possible deployment scenarios is beyond the scope of this document the following table describes some of the more common causes and possible solutions Cause Possible Solution The sea bottom or target is outside the altimeter s bea...

Страница 43: ...ditional targets are being detected outside the range window This may be seen as erratic altitude measurements due to noise mid water targets or multipath interference These can be filtered out by judicious adjustment of the minimum maximum range increasing the minimum threshold and decreasing the TVG gain offset Select the peak return decision method for bottom tracking applications If necessary ...

Страница 44: ...altimeter used in several applications such as bottom profiling and forward looking obstacle avoidance deployments This appendix describes the methods used to determine the altitude return values from the sampled sonar data The following figure shows a typical altimeter return signal Min Width Setting Min Gap Setting Min Range Setting Min Width Setting Threshold Setting A D E F G H M N A m p l i t...

Страница 45: ...onar data will be detected as returns This is usually set high enough so that small unwanted targets and noise such as at B do not become detected as returns Return samples are then evaluated proceeding to longer ranges There may be low level returns and noise that are ignored because they are below the threshold At some point C the signal rises above the threshold at the start of a potential retu...

Страница 46: ...uilt up in the PEAK RETURN mode Once all potential returns have been found to the end of the ping the program then chooses the altitude value from the return that has the highest amplitude Referring to the figure above a second return was found at H with an amplitude N the program would then use the altitude H with amplitude N Care must be used when employing the PEAK RETURN mode This mode is not ...

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