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Metadata Report for BODC Series Reference Number 438942


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type
NameCategories
Aanderaa RCM 7/8 Recording Current Meter  current meters
Instrument Mounting subsurface mooring
Originating Country United Kingdom
Originator -
Originating Organization Proudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Land Ocean Interaction Study (LOIS)
LOIS Shelf Edge Study (LOIS - SES)
 

Data Identifiers

Originator's Identifier as09928.768
BODC Series Reference 438942
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1996-04-18 14:15
End Time (yyyy-mm-dd hh:mm) 1996-07-30 11:45
Nominal Cycle Interval 1800.0 seconds
 

Spatial Co-ordinates

Latitude 56.46170 N ( 56° 27.7' N )
Longitude 9.16250 W ( 9° 9.8' W )
Positional Uncertainty 0.5 to 1.0 n.miles
Minimum Sensor or Sampling Depth 31.0 m
Maximum Sensor or Sampling Depth 31.0 m
Minimum Sensor or Sampling Height 668.0 m
Maximum Sensor or Sampling Height 668.0 m
Sea Floor Depth 699.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor or Sampling Depth Datum Sea floor reference - Depth measured as a height above sea floor but converted into a depth relative to the sea surface according to the same datum as used for sea floor depth (applicable to instrument depths not bathymetric depths)
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
CNDCPR011Siemens per metreElectrical conductivity of the water body by in-situ conductivity cell
LCDAEL011Degrees TrueDirection (towards) of water current (Eulerian measurement) in the water body by in-situ current meter and correction to true North
LCSAEL011Centimetres per secondSpeed of water current (Eulerian measurement) in the water body by in-situ current meter
PREXPR011DecibarsPressure (measured variable) exerted by the water body by semi-fixed in-situ pressure sensor and corrected to read zero at sea level
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPPR011Degrees CelsiusTemperature of the water body

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

Noisy periods in current speed record and some unusually high speeds which are not supported by data from other meters on the rig. Use with caution.

Pressure and current data from the meters on this rig indicate that it was disturbed and damaged between 21:00h 9th May and 01:30h 10th May 1996.

Data Quality Report

Exceptional variability in the temperature signal indicates that the instrument was subject to oscillations of the thermocline.


Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."


Narrative Documents

Aanderaa Recording Current Meter Model 7/8

Manufacturer's specifications: recording unit height 49.5cm (RCM8 52.0cm), diameter 12.8cm, vane size 48.5x50.0cm. Meter is designed for depths down to 2000m (RCM8 6000m). It incorporates a spindle which is shackled to the mooring line. The meter is attached to the spindle through a gimbal mounting which permits a maximum 27° deviation of the spindle from the vertical, the meter still remaining horizontal.

Meter comprises :

  1. Paddle wheel rotor magnetically coupled to an electronic counter

  2. Vane, which aligns instrument with current flow, has a balance weight ensuring static balance and tail fins to ensure dynamic balance in flows up to 250cm/s.

  3. Magnetic compass (needle is clamped to potentiometer ring) - direction recorded with 0.35° resolution, 5° accuracy for speeds 5 to 100cm/s, 7.5° accuracy for remaining speeds within 2.5 to 200cm/s range.

  4. Quartz clock, accuracy better than 2 sec/day within temperature range 0 to 20°C.

  5. Thermistor (temperature sensor), standard range -2.46 to 21.48°C (max on high range 36.04°C), accuracy 0.05°C, resolution 0.1 per cent of range, 63 per cent response time 12sec.

  6. Inductive cell conductivity sensor (optional), range 0 to 70mmho/cm standard resolution 0.1 per cent of range.

  7. Silicon piezoresistive bridge, standard range 0 to 3000 psi (RCM8 to 9000 psi), resolution 0.1% of range.

  8. Self balancing potentiometer which converts the output from each sensor into a 10 bit binary number for storage on magnetic tape.

  9. Associated electronics.

A built-in clock triggers the instrument at preset intervals and up to six channels are sampled in sequence. Channel 1 is a fixed reference reading for control purposes and data identification. Channels 2, 3 and 4 represent measurement of temperature, conductivity and pressure. Channels 5 and 6 represent the VECTOR AVERAGED current speed and direction since the previous triggering of the instrument. The number of rotor revolutions and the direction is sampled every 12 seconds and broken into North and East components. Successive components are added and recorded as speed and direction. For recording intervals longer than 10 minutes, speed and direction are sampled 1/50th of recording interval.

It has become common practice in some laboratories to deploy these meters as temperature and conductivity loggers without current measuring capabilities.

The following link will provide the manufacturer specifications:

Manufacturer specifications

Aanderaa Current Meter Data Processing

Data Originator's Processing

The following procedures are carried out before the data were supplied to BODC.

Data were downloaded from the instrument logger, and factory calibrations were applied to the current speed channel, and the pressure, conductivity and temperature channels when fitted. Where available, laboratory calibrations of the current direction channels were used; factory formulae were used in their absence. Where no form factor was known for the conductivity sensor, a value of 2.8 was used.

Please note (concerns vector averaged current data): The current data are averaged by the logger over the sampling interval, whereas the pressure, temperature and conductivity data are single point measurements taken at the end of the interval. The data originator has moved the time stamps to the mid-point of the vector averaging sampling interval for all channels without interpolation.

BODC Data Processing and Quality Control

Where pressure sensors were fitted: the data record was compared with the pressure computed from the water depth on deployment and rig geometry. The time series was visually screened for evidence of rig movement (e.g. trawling) and excessive leaning (perhaps due to strong currents).

Where temperature sensors were fitted: the data record was compared with calibrated CTD data taken in the vicinity and checked for agreement within a few tenths of a degree Celsius. Obvious spikes were flagged. Periods of excessively noisy data were noted.

Where conductivity sensors were fitted: salinity (PSS-78) was computed from in-situ temperature and conductivity and a nominal pressure computed from the water depth on deployment and rig geometry. Obvious spikes were flagged.

BODC Current Meter Screening

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

  • Irregularities such as unfeasible values
  • Inconsistencies between related information. For example:
    • Depths of meter and sea bed.
    • Times for mooring deployment and for start/end of data series.
    • Length of record or number of data cycles, the cycle interval, the clock error and the period over which accrued.
    • Parameters stated as measured and the parameters actually present in the data cycles.
  • Originator's comments on meter/mooring performance and data quality.

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non- oceanographic origin may be tagged with the BODC flag denoting suspect value.

The following types of irregularity, each relying on visual detection in the time series plot, are amongst those which may be flagged as suspect:

  • Spurious data at the start or end of the record.
  • Obvious spikes occurring in periods free from meteorological disturbance.
  • A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities, deemed abnormal, then instead of flagging the individual suspect values, a caution may be documented. Likewise documents will highlight irregularities seen in the current vector scatter plots such as incongruous centre holes, evidence of mooring 'knock-down', abnormal asymmetry in tidally dominated records or gaps as when a range of speeds or directions go unregistered due to meter malfunction.

The term 'knock-down' refers to the situation when the 'drag' exerted on a mooring at high current speeds may cause instruments to tilt beyond the angle at which they are intended to operate. At this point the efficiency of the current sensors to accurately record the flow is reduced.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought, and where necessary, documented. This covers inconsistencies in the following:

  • Maximum and minimum values of parameters (spikes excluded).
  • The orientation and symmetry of the current vector scatter plot.
  • The direction of rotation of the current vectors.
  • The approximate amplitude and periodicity of the tidal currents.
  • The occurrence of meteorological events and, finally, for series for which no time check was possible, the phase.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Data Processing Notes

Instrument recorded pressure appears not to accurately reflect instrument depth. Therefore salinity has been computed using a nominal pressure derived from the rig configuration and water depth on deployment.


Project Information

Land Ocean Interaction Study (LOIS)

Introduction

The Land Ocean Interaction Study (LOIS) was a Community Research Project of the Natural Environment Research Council (NERC). The broad aim of LOIS was to gain an understanding of, and an ability to predict, the nature of environmental change in the coastal zone around the UK through an integrated study from the river catchments through to the shelf break.

LOIS was a collaborative, multidisciplinary study undertaken by scientists from NERC research laboratories and Higher Education institutions. The LOIS project was managed from NERC's Plymouth Marine Laboratory.

The project ran for six years from April 1992 until April 1998 with a further modelling and synthesis phase beginning in April 1998 and ending in April 2000.

Project Structure

LOIS consisted of the following components:

  • River-Atmosphere-Coast Study (RACS)
    • RACS(A) - Atmospheric sub-component
    • RACS(C) - Coasts sub-component
    • RACS(R) - Rivers sub-component
    • BIOTA - Terrestrial salt marsh study
  • Land Ocean Evolution Perspective Study (LOEPS)
  • Shelf-Edge Study (SES)
  • North Sea Modelling Study (NORMS)
  • Data Management (DATA)

Marine Fieldwork

Marine field data were collected between September 1993 and September 1997 as part of RACS(C) and SES. The RACS data were collected throughout this period from the estuaries and coastal waters of the UK North Sea coast from Great Yarmouth to the Tweed. The SES data were collected between March 1995 and September 1996 from the Hebridean slope. Both the RACS and SES data sets incorporate a broad spectrum of measurements collected using moored instruments and research vessel surveys.


LOIS Shelf Edge Study (LOIS - SES)

Introduction

SES was a component of the NERC Land Ocean Interaction Study (LOIS) Community Research Programme that made intensive measurements from the shelf break in the region known as the Hebridean Slope from March 1995 to September 1996.

Scientific Rationale

SES was devoted to the study of interactions between the shelf seas and the open ocean. The specific objectives of the project were:

  • To identify the time and space scales of ocean-shelf momentum transmission and to quantify the contributions to ocean-shelf water exchange by physical processes.

  • To estimate fluxes of water, heat and certain dissolved and suspended constituents across a section of the shelf edge with special emphasis on net carbon export from, and nutrient import to, the shelf.

  • To incorporate process understanding into models and test these models by comparison with observations and provide a basis for estimation of fluxes integrated over time and the length of the shelf.

Fieldwork

The SES fieldwork was focussed on a box enclosing two sections across the shelf break at 56.4-56.5 °N and 56.6-56.7 °N. Moored instrument arrays were maintained throughout the experiment at stations with water depths ranging from 140 m to 1500 m, although there were heavy losses due to the intensive fishing activity in the area. The moorings included meteorological buoys, current meters, transmissometers, fluorometers, nutrient analysers (but these never returned any usable data), thermistor chains, colour sensors and sediment traps.

The moorings were serviced by research cruises at approximately three-monthly intervals. In addition to the mooring work this cruises undertook intensive CTD, water bottle and benthic surveys with cruise durations of up to 6 weeks (3 legs of approximately 2 weeks each).

Moored instrument activities associated with SES comprised current measurements in the North Channel in 1993 and the Tiree Passage from 1995-1996. These provided boundary conditions for SES modelling activities.

Additional data were provided through cruises undertaken by the Defence Evaluation and Research Agency (DERA) in a co-operative programme known as SESAME.


Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1996-04-18
End Date (yyyy-mm-dd) 1996-08-01
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#768
Platform Categorysubsurface mooring

Proudman Oceanographic Laboratory Moored Instrument Rig #768

This rig was deployed as part of the LOIS Shelf-Edge Study at site S700.

Rig position: 56° 27.70'N 09° 09.75'W
Deployed: 18 Apr 1996 13:55
from RRS Challenger (cruise CH126A)
Recovered: 01 Aug 1996 11:27
onto RRS Challenger (cruise CH128B)

The instruments were anchored by 1000kg of chain and kept erect by a 48" diameter buoy attached 25m below the sea surface.

Instruments deployed on the rig

Height above
Sea Bed
Instrument
668m Aanderaa current meter (#9928)
666m to 590m 76m thermistor chain (#1185)
589m Aanderaa current meter (#9450)
587m to 487m 100m thermistor chain (#1688)
451m Aanderaa current meter (#9927)
381m to 181m 200m thermistor chain (#1758)
108m Aanderaa current meter (#11216)
38m to 13m 25m thermistor chain (#1684)
8m Chelsea Instruments fluorometer (#13)
7m Aanderaa current meter (#11814)
fitted with SeaTech transmissometer (#556)

Related Data Activity activities are detailed in Appendix 1

Cruise

Cruise Name CH126A
Departure Date 1996-04-11
Arrival Date 1996-04-26
Principal Scientist(s)Paul Tett (Napier University School of Life Sciences)
Ship RRS Challenger

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameLOIS(SES) S700
CategoryOffshore location
Latitude56° 27.14' N
Longitude9° 9.50' W
Water depth below MSL700.0 m

LOIS (SES) Mooring and CTD Site S700

Site S700 was a fixed station where moorings were deployed during the Land-Ocean Interaction Study (LOIS) Shelf Edge Study (SES). It was also one of fourteen CTD sites on repeat section S, across the Hebridean Slope, occupied by cruises between March 1995 and September 1996.

Instrument Deployment History

The following tables summarise the instruments deployed at this site for which data may be available.

1995

Mar Apr May Jun Jul Aug Sep Oct Nov Dec
CM a   b b b b c      
TChn     a a a a b      
Tr     a a            
Fl     a a b b c      
NA     a a b b        

1996

Jan Feb Mar Apr May Jun Jul Aug
CM   d d d e e e e
TChn   c c c d d d d
Tr                
Fl         d d d d
NA                

Each different letters in the table above corresponds to an individual instrument record.

Glossary

  • CM = Current meter (Aanderaa or S4)
  • BPR = Bottom pressure recorder
  • ADCP = Acoustic Doppler Current Profiler
  • TChn = Thermistor chain
  • Tr = Transmissometer
  • Fl = Fluorometer
  • NA = Nutrient analyser

Note

  1. Transmissometers may have been fitted to some of the current meters.
  2. Other instruments (colour sensors) may have been deployed.
  3. Only periods for which useful data were returned are shown.

Related Fixed Station activities are detailed in Appendix 2


BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
Q value below limit of quantification

Appendix 1: POLRIG#768

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Series IdentifierData CategoryStart date/timeStart positionCruise
442480Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442523Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442535Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
476187Fluorescence or pigments1996-04-18 14:02:5656.4617 N, 9.1625 WRRS Challenger CH126A
438917Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
438930Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439017Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439459Currents -subsurface Eulerian1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A
442511Hydrography time series at depth1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A

Appendix 2: LOIS(SES) S700

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Series IdentifierData CategoryStart date/timeStart positionCruise
496115Transmittance/attenuance, turbidity, or SPM conc.1995-03-27 18:20:4056.4517 N, 9.1585 WRRS Charles Darwin CD91B
439195Currents -subsurface Eulerian1995-03-29 10:38:0056.4622 N, 9.1613 WRRS Charles Darwin CD91B
436161Currents -subsurface Eulerian1995-03-29 10:55:0056.4622 N, 9.1613 WRRS Charles Darwin CD91B
496103Transmittance/attenuance, turbidity, or SPM conc.1995-05-10 20:00:0056.4532 N, 9.158 WRRS Charles Darwin CD93A
476218Fluorescence or pigments1995-05-10 20:02:5656.4532 N, 9.158 WRRS Charles Darwin CD93A
439619Hydrography time series at depth1995-05-10 20:30:0056.4532 N, 9.158 WRRS Charles Darwin CD93A
476114Fluorescence or pigments1995-05-11 13:02:5756.4605 N, 9.1642 WRRS Charles Darwin CD93A
439552Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439681Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439785Hydrography time series at depth1995-05-11 13:30:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
426098Currents -subsurface Eulerian1995-05-11 13:32:3056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431236Currents -subsurface Eulerian1995-05-11 13:44:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431297Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
431457Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439251Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
439263Currents -subsurface Eulerian1995-05-11 13:45:0056.4605 N, 9.1642 WRRS Charles Darwin CD93A
390247CTD or STD cast1995-07-27 14:35:0056.4812 N, 9.1477 WRRS Challenger CH120
1287248Water sample data1995-07-27 14:35:0056.4812 N, 9.1477 WRRS Challenger CH120
476126Fluorescence or pigments1995-08-13 15:02:5756.4602 N, 9.1627 WRRS Challenger CH121A
426105Currents -subsurface Eulerian1995-08-13 16:42:3056.4602 N, 9.1625 WRRS Challenger CH121A
431248Currents -subsurface Eulerian1995-08-13 16:55:0056.4602 N, 9.1625 WRRS Challenger CH121A
439275Currents -subsurface Eulerian1995-08-13 16:55:0056.4602 N, 9.1625 WRRS Challenger CH121A
431304Currents -subsurface Eulerian1995-08-13 16:56:0056.4602 N, 9.1625 WRRS Challenger CH121A
439693Hydrography time series at depth1995-08-13 17:03:0056.4602 N, 9.1625 WRRS Challenger CH121A
439797Hydrography time series at depth1995-08-13 17:15:0056.4602 N, 9.1625 WRRS Challenger CH121A
439564Hydrography time series at depth1995-08-14 17:03:0056.4602 N, 9.1625 WRRS Challenger CH121A
436277Currents -subsurface Eulerian1996-02-05 17:45:0556.4648 N, 9.1635 WRRS Challenger CH125A
442443Hydrography time series at depth1996-02-05 18:00:0056.4648 N, 9.1635 WRRS Challenger CH125A
442406Hydrography time series at depth1996-02-05 18:00:0456.4648 N, 9.1635 WRRS Challenger CH125A
442431Hydrography time series at depth1996-02-05 18:00:0456.4648 N, 9.1635 WRRS Challenger CH125A
436204Currents -subsurface Eulerian1996-02-05 18:15:0456.4648 N, 9.1635 WRRS Challenger CH125A
442480Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442523Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
442535Hydrography time series at depth1996-04-18 14:00:0056.4617 N, 9.1625 WRRS Challenger CH126A
476187Fluorescence or pigments1996-04-18 14:02:5656.4617 N, 9.1625 WRRS Challenger CH126A
438917Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
438930Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439017Currents -subsurface Eulerian1996-04-18 14:15:0056.4617 N, 9.1625 WRRS Challenger CH126A
439459Currents -subsurface Eulerian1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A
442511Hydrography time series at depth1996-04-18 14:30:0056.4617 N, 9.1625 WRRS Challenger CH126A
496176Transmittance/attenuance, turbidity, or SPM conc.1996-04-18 16:36:0056.4702 N, 9.1633 WRRS Challenger CH126A
442560Hydrography time series at depth1996-04-18 17:00:0056.4702 N, 9.1633 WRRS Challenger CH126A
506098PAR radiance and irradiance1996-04-19 12:11:0056.4702 N, 9.1633 WRRS Challenger CH126A