Hydrocamp : Kennebecasis Bay 2010
Operational Planning and Compilation of Existing Data
Contents:

Background

As always, the GGE5083 Hydrographic Field Operations Course ("Hydrocamp") is designed to provide the first serious practical training in the design, implementation, processing and production of a coastal hydrographic survey.

regional locationFor 2010, the location will be the Kennebecasis Estuary just north of Saint John.  This region has been a focus of OMG investigations for the past few years. See:
http://www.omg.unb.ca/Oceano/lowerSaintJohn/OMG_UNB_Saint_John_River_Studies.html

The only official CHS chart of the region (4141) is predominantly based on a 1937 (?) lead line survey.  In addition, it has previously been almost completely resurveyed by the Ocean Mapping Group as part of earlier research and training programs. EM3000 and EM3002 multibeam data exist from 1996 to 2009 (see detailed compilation below).  The data quality for these surveys varies widely however. As a result the older data need reprocessing and reassessment.

Hydrocamp will involve reprocessing and reassessment of the archived data, followed by the deployment of the CSL Heron with its new EM710 to conduct resurveying of the imperfect sections. In addition, a 3.5 kHz investigation of landslides will be conducted (see details below).

Study of Landslides

As part of the gradual compilation, it became apparent that a series of buried landslides exist in the Kennebecasis. 7 slides have been identified.
all slides

In 2005 an attempt was made to undertake a subbottom profile grid over each slide. In order to increase the resolution the acquisition range window of the Knudsen was set to 25m only (normally it is 50 or 100m). At the time it was not appreciated how deeply these slides were buried. As a result of phasing of the logged range, the profiles often did not even penetrate down to the upper surface of the slide.

The following 4 animations show the series of profiles obtained over 4 of the seven slides.  It is clear that the slides are buried by at least 10m of mud and thus the features are only partly imaged at this time. An aim therefore, of this Hydrocamp, is to redo these 3.5 kHz subbottom surveys to better define the slides.


 map 2
 map 3 map 4 map 5

map 2
 map 3 map 4 map 5







Operational Plan:

The 2010 GGE5083 Hydrocamp will take place in the Kennebecasis Bay (technically an estuary or more strictly a fjord), just north of Saint John.  We'll be working out of the Saint John Marina in Grand Bay (all above the Reversing Falls).

The camp will consist of 8 components:


PRE-CAMP WORK : -----------

 1 - reprocessing EM3000 and EM3002 data collected in the region from 1996-2009 (CSL Plover and CSL Heron).
 
The necessary steps are described in detail below.

The main steps are:
2 - reprocessing a subset of the 3.5 kHz subbottom already collected.

3 - reprocessing an old set of MVP (CTD) measurements from along the fjord

4 - compiling all the surrounding terrestrial orthophoto and topographic information (mainly from Service New Brunswick).


CAMP HYDROGRAPHIC SURVEY ---- (~ 1st to 15th May)

5 - undertaking a new EM710 multibeam survey of a subsection of the fjord. This will involve:
*** NOTE -  should there be technical delays in the installations on the Heron, this will be shifted by a few weeks until the end of May.


CAMP GEOPHYSICAL SURVEY --- done sometime within ~ 15th to 30th May? (when Karl is available).
 
6 - undertaking a dense 3.5 kHz subbottom survey of the buried slides.

7 - hopefully... undertaking a towed Magnetometer survey in the vicinity of the wrecks. Karl Butler has a base station for reduction for dirunal variability.

7A - there  was a remote possibility that we'd be able to borrow a small airgun to do a multichannel  seismic line, but I think this is now v. unlikely.
 
FINAL PRODUCTION ---------------

8 - production of a map product (Arc) showing:
    - regional terrestrial data (orthophotos, coastlines, contours).
    - seabed bathymetry
    - seabed backscatter.
   - with insets showing seismic sections - and isopachs of slide thickness and extent..
    - and an inset showing the longitudinal MVP section

- as part of all of this a detailed report on:

8A - whatever magnetic processing we can do

---------------------------------------------------------------


Background Image Derivation

Orthophoto Compilation

To compile the SNB orthophotos that cover the Kennebecasis  Bay region. You can get them all from SNB through the UNB library portal at:

http://www.lib.unb.ca/gddm/maps/SNB/sodb.html

You have to select the  5 minute lat by 10 minute lon map sheets based on the file name (think it is the lower left coordinate e.g. 44556710).  You get a MrSiD image file along with a tif world file using NB double sterographic projection ..

You should be able to get the ~5-8 images that cover the whole Kennebecasis and import them into Arc. Make a project showing the composite of  all the photos.


EM3000 Reprocessing:

Data Location and Assignment

Copies of the unravelled data from the various surveys listed below have been put on:
    /drives/nootka/disk1/Hydrocamp_2010

The main datasets, the person to be assigned to them, and their location are:

YEAR
PERSON ASSIGNED
 DATA LOCATION
2000
 Yun Ta
 /drives/nootka/disk1/Hydrocamp_2010/2000_Plover_Kenne/
2002A and B
 Hesham
 /drives/nootka/disk1/Hydrocamp_2010/2002_plat_Kenne/ 
         and 2002_plat_Kenne2/
2003
 Majed
 /drives/nootka/disk1/Hydrocamp_2010/2003_Heron_GrandBay/
2004
 Tyson
 /drives/nootka/disk1/Hydrocamp_2010/2004_Heron_Kenne/
2005
 Travis /drives/nootka/disk1/Hydrocamp_2010/2005_Heron_Kenne/

All are EM3000 data. All the datasets are copies of our archives, so if you happen to corrupt or wipe out some data, you can recreate it.  You need to become familiar with our standard directory structure. Each data set has its unique problems and history. 

you need to slowly become familair with the swathed processing tools.


Unravelling:

For these data, they should already be unravelled in the OMG format. Initially, accept the existing data.
For the purposes of reducing the backscatter strength, the data are missing the "R0" value, so we may reunravel the data (see later discussion). 

Should you need to reunravel the raw data, the scripts are here:
Make your own custom work directories (e.g. : /drives/nootka/disk1/Hydrocamp_2010/Travis etc..).  In these you will generate all your personal products.

Vertical Control:

For your assigned survey data you need to get holds of the Archived water levels for:

SAINT JOHN RIVER AT SAINT JOHN (01AP005)

As far as I can see, the online archived data is now only the daily average. You should talk to Steve Brucker to see about getting the hourly water levels (we have some years, not all).

in:      /homes/share/datasets/ST_JOHN_RIVER_WATERLEVELS
you will find:     Hourly_1996to2006_01AP005_version2_St_John.xls

From this create a binary tide file and remerge with the provided data.

Determine the range of time that the Heron/Plover was used for you surveys (>getBounds merged/*/*.merged or by individual  subdirectories in the merged directory) .  Make a plot of the tide for those periods (in some cases there are 2 or 3 periods of several days separated by weeks or month).  Make a plot that shows when the data was collected during that period
(>plotTide -start 2002 130 0 0 -end 2002 135 0 0 -infile tide.bin merged/*/*.merged).


The site of this gauge is at Indiantown, just above the Reversing Falls. Where you are operating is upstream of this from Millidgeville to Gondola Point.  Take a look at the CHS Blue file for constituents for the tides at other sites along the Kennebecasis (Rothesay, Renforth).  Should we be applying a time delay and/or an amplitude scaling to the Indiantown gauge?

The Environment Canada Gauges are all referenced to the geoid. For the EM710 operations, you are going to collect PPK data. You thus need to establish :
  1. the Elliposid to Geoid separation at the base station.
  2. the shape of that separation surface along the Kennebecasis.
  3. the Geoid to Chart datum separation at the base station (the tide gauge benchmark at Saint John Marina probably).



Map Sheet Construction:

map sheetsYou need to design a series of mapsheets to cover the whole fjord. Something like the image here:

You can try options using the following scripts:
 
Ultimately we will want data gridded at the finest achievable resolution (1m in the shallows, 2m deep). But we are also looking for the overview mpproduct. Possibly a rotated mapsheet.

You should learn how to pick a rotated map sheet (that most efficiently covers the assigned data for you area). 


Gridding

Once you've merged the tides, you  should grid the data into the 4 mapsheets:
> weigh_grid -beamwidth 1.0 -cw EM3000_weights  mapsheet_prefix    .../200X_Vessel_Area/EM3000/merged/JDXXX/*.merged

Remember you mneed to make three floating point arrays : prefix.r4, prefix.r4_weighs, prefix.r4_weight_depth

Removing Long Period Heave Drifting

For much of these data sets, the Heron is turning rapidly and accelrating and decelerating. As a result, the heave signal recorded either by the MRU-6 or the F180, is showing an impulse response that results in a long period drift in the heave soution that is not in fact experienced by the vessel. As a result you will notice that the lines do not match each other well bathymetrically at the start and end of lines. To fix this, you need to extract a low pass filtered version of the heave signal. This is done using "fix_TimeSeries":

> fix_TimeSeries -heave_drift -avpings 30 merged/subdir/006*.merged

** be very careful to see which motion time series you are using. For many of the surveys, the Heron was logging two motion sensors : the MRU-6 and the F-185.  When you run "mergeAtt" in the unravel script, it chooses one or the other. 

time series toolYou can then see the effect in swathed. Look at the list window and you will see that the "Hv. (lpf)" field is non zero. You can plot this out in the Time Series window (figure to left - derived by pressing the "Heave" button and adjusting the vertical scale of each plot using the up and down arrow keys).
Try altering the heave filter period cutoff by pressing the left key in the top centre widget.  If you like the value (I'd recommend ~ 20-30 econds), use that value in fix_Timeseries and apply it to all the data.


To use this correction in the final grid you need to add a term to the weigh_grid command:

> weigh_grid -add_dyn_draft_shift  -fresh_start  -custom_weight EM3000_weights -beamwidth 1.0 themap.drift_corr   ..............

Make another copy of the r4 and repeat the gridding using the "dynamic draft shift adjustment". Sun illuminate the two versions of the grid to compare the resulting surface.  You can use differ:

> differ -first the_map.usual.r4 -second the_map.drift_corr.r4 -out the_map.drift_corr_difference.r4
> r4to8bit -low -0.3 -high 0.3 the_map.drift_corr_difference.r4
> jview the_map.drift_corr_difference.r4 &

This will allow you to see the scale of the diffrence in the two grids. THe error is smnall ( a few decimeres, but that is a large percentage of your IHO Special Order budget.

Residual Bathymetric Data Cleaning

Based on the quality of the observed grid, you may feel the need to edit out bad datasets. Do so and try regridding.

Removing Transit Lines and Redundant Data

As part of all these surveys, there is always a few lines that would be better off removed. These need to be identified and removed from the merged_list files.

Sidescan Strip Creation.

for some, but not all of these surveys ,strips of sidescan have already been generated.  We would like you to recereate all the diffrent versions of the sidescna (multibeam backscatterdaata):
As part of this there are two scripts available:

You then need to make a separate mosaic of each of the data types...


Existing Data:

CHS Chart (4141):
The chart is available as a BSB.  In addition, one of two analog hand drawn field sheets from the 1930's is available.

CHS single beam archives:
Somewhere we have a digital file of the single beam soundings for the lower river...

Existing Multibeam Data:
The following set of maps and descriptions identify the EM3000 and EM3002 multibeam surveys that have been undertaken in the Kennebecasis since 1996:

Navigation Track
 Vessel - Sonar - Ancillary Instrumentation
1996 data
 CSL Plover June 1996: As part of a transit down the Saint John River in 1996, the CSL Plover, with an EM3000 paused aboved the Reversing Falls, waiting  for the slack water period.
  • Sonar : EM3000
  • Positioning : DGPS - Coastguard Corrections
  • Motion : POS/MV 310
  • Sound Speed Data  - unlikely to have measured one.
  • Vertical Datum :  Environment Canada  Indiantown Gauge..
1996 data CSL Plover May 2000: As part of Hydrocamp 2000, about a week of EM3000 data was acquired of the western Kennebecasis, based out of the RKYC.
  • Sonar : EM3000
  • Positioning : DGPS - a mix of Coastguard Corrections and UNBSJ rooftop base station
  • Motion : POS/MV 310
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum : local gauge installed at RKYC (unreliable) and - Indiantown Gauge..
1996 data CSL Heron April 2002: As part of the first trials of the CSL Heron in April 2002, the
  • Sonar : EM3000
  • Positioning : DGPS -  Coastguard Corrections
  • Motion : Seatex Seapath 200 (?) - with MRU6 backup
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Environment Canada Indiantown Gauge.
2002 navigation tracks. CSL Heron Nov. 2002: At the end of the season, two days were used to expand the coverage of the Kennebecasis.
  • Sonar : EM3000
  • Positioning : DGPS -  Coastguard Corrections? or Racal Landstar
  • Motion : MRU6 with speed aiding
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Manual tidestaff readings at Saint John Marina and Environment Canada Indiantown Gauge.
2003 navigation tracks CSL Heron May 2003: Hydrocamp 2003 took place in Grand Bay and the Westfield Channel, based out of the Saint John Marina.
  • Sonar : EM3000
  • Positioning : DGPS -  Coastguard Corrections (or  Racal Landstar?)
  • Motion : MRU6 with speed aiding
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Automated tidegauge at Saint John Marina and Environment Canada Indiantown Gauge.
2004 navigation tracks CSL Heron Sept. 2004: At the end of the field season, the Heron was used for GGE3353 undergraduate training and undertook an extra 2 days of mapping in the Kennebecasis.
  • Sonar : EM3000
  • Positioning : DGPS -  Coastguard Corrections  or CNav?
  • Motion : Coda Octopus F180 with backup of MRU6 with speed aidingAll_Kenn.Combo.sun_315
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Environment Canada Indiantown Gauge.
2005 navigation tracks CSL Heron May-June 2005: In May, inital tests prior to Hydrocamp 2005 off Deer Island were undertaken (with a bad motino sensor). After the camp the vessel returned prior to deployment to Quebec City (where she was subsequently sunk).
  • Sonar : EM3000
  • Positioning : CNav
  • Motion : May - MRU6 only (no speed aiding , June  Coda Octopus F180
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Environment Canada Indiantown Gauge.
2008 navigation tracks CSL Heron Nov. 2008: As part of a break in the oceanographic tidal cycle program in Saint John harbour, the Heron was used to resurvey the entire gorge upstream of the Reversing Falls.
  • Sonar : EM3002
  • Positioning : CNav
  • Motion : M Coda Octopus F185
  • Sound Speed Data  - multiple SVP's.
  • Vertical Datum :  Environment Canada Indiantown Gauge.
2009 navigation tracks CSL Plover Oct. 2009: While waiting out a storm , the Plover, based off the CCGS Mattherw, came above the falls at UNB request to resurvey the erosional flutes in the Westfield channel.
  • Sonar : EM3002
  • Positioning : Fugro OmniStar
  • Motion : POS/NV 320 v.4
  • Sound Speed Data  - twice daily SVP's.
  • Vertical Datum :  Environment Canada Indiantown Gauge.

Archived Oceanographic Transects:

November 2002 - using the Valeport Winch, the MVP was deployed along the full section.

2003 - details transects from Grand Bay to Head of the Bluff
2005 - two long MVP sections.


page created by John E. Hughes Clarke, February/March, 2010