Bathymetry - ASR - Waihou River Delta Firth of Thames

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2011 Bathymetry Shapefile - Waihou

File Identifier: EE2F2110-BB44-40BC-B566-5C31737C36C6 Parent Identifier: B8DEE7E8-1ED1-4950-AA6B-3B4E51074CCD Hierarchy Level: feature Hierarchy Level Name: feature of Bathymetry - ASR - Waihou River Delta Firth of Thames Abstract: Bathymetry survey of the Waihou River delta, Firth of Thames by ASR Ltd Marine Consulting and Research in June 2011. Statement: Bathymetric survey within the Firth of Thames approximately 4 by 7 km encompassing the main body of the delta. Other Information: Method: A LOWRANCE LMS-525 single-beam echo sounder operating at 200 KHz working in conjunction with a GPS unit, recorded depth and position data in real-time to a palmtop computer. Bar tests were conducted at regular intervals to test the sonar and quantify the vertical accuracy of the measurements. The sounder has a temperature sensor which is used to automatically compensate for water temperature effects on the speed of sound through water. The results of the calibration tests showed that the sounder was always within the instruments specifications (i.e. +/- 0.1 m). Note, a further ±0.15 m is generally considered to account for boat movement, however, this type of error cancels itself out, i.e. it is not a consistent offset error such as can occur with an inaccurate instrument. Survey: The bathymetric survey was conducted during daylight hours between 30th of May and the 21st of June 2011. Figure 2 shows the geographical location of each sounding collected during the survey. The chart verification lines, collected west of the delta, are 5-6km in length and orientated approximately shore-normal. Parallel track lines with 50 m spacing, orientated at ~326° (~146° reciprocal) were followed throughout the survey of the Delta. An exception to this is data that was collected on the Eastern shore of the Firth, where tracklines were orientated shore normal. Additional data was collected outside the original 4 by 7 km box, specifically in regions where LIDAR measurements are deficient. Data collected in these areas will greatly benefit any subsequent numerical modelling. These regions include the mouth of the Piako River and an area to the East of the Waihou River mouth approximately 0.6 km2. Figure 3 shows that sufficient, relatively evenly spaced coverage was obtained to accurately define the bathymetry within the survey area. Raw depth data was tidally corrected to Tararu mean sea level using data from the Tararu tide gauge located in the Firth of Thames (Figure 2 insert) and a transducer offset of 0.4 m was added to each depth measurement. Positional data was recorded in the World Geodetic System 1984 (WGS84) and converted to New Zealand Map Grid (NZMG). Depths have also been reduced to chart datum in order to make a comparison with nautical charts. This was achieved by using the following datum offsets: · Tararu MSL to Auckland 1946: + 0.128 m · Auckland 1946 to Chart Datum (Auckland and West Coast Coromandel): +1.742 m Gridding: The corrected data was gridded using Kriging interpolation in SURFER® software. Kriging is a geostatistical gridding method that has proven useful and popular in many fields. This method produces visually appealing contour and surface plots from irregularly spaced data. Kriging expresses trends in data, so that, for example, high points might be connected along a ridge, rather than isolated by bull's-eye type contours that would be obtained from linear interpolating. Kriging always uses the measured value exactly (known as an “exact” interpolator) when it coincides with the grid node in the gridded data file. Survey track lines were mostly perpendicular to seabed gradients, as a result seabed features are well represented in the bathymetry. ASR has previously carried out tests of kriging with survey data (Mathew et al. 2000) and concluded that kriging interpolation is the best possible method to accurately grid irregular bathymetry survey data and that values for known points in the data and grids are identical. Additional Data Sets: Figure 3 shows the overlap achieved during the survey with the available LIDAR data. The blue box shows a region, the Waihou River, where high resolution data has been collected during a recent survey conducted by ASR Ltd. This data will be made available for any subsequent modeling. Figures referred to in Survey Report DOC# 3119895 WRC, at its discretion, may charge for access to or extraction of this data at a Technical Officer rate of $140 per hour plus GST. Bathymetry Data is available under the Creative Commons Attribution 4.0 International license (CC BY 4.0). Keywords: Bathymetry,Depth,Elevation,River,Survey Topic Category: elevation:height above or below sea level Resource Reference Date: 15/01/2016 Metadata Constraints Access Constraints: copyright Use Constraints: copyright Maintenance Information Maintenance frequency: static Last Load Date: 10/01/2019 Spatial Representation Information Recommended Scale: Reference System: EPSG2193 Spatial Representation Type: vector Vector Grid Geographic Bounding Box GeometricObjectType : point geometricObjectCount : topologyLevel : geometryOnly Number of Dimensions : 2 Cell Geometry : Transformation Param Available : N westBoundLongitude : 1825277 eastBoundLongitude : 1808738 southBoundLatitude : 5881740 northBoundLatitude : 5890104 Responsible Parties Role: owner Position: Organisation: Waikato Regional Council Delivery Point: 160 Ward Street City: Hamilton Central Postal Code: 3204 Country: New Zealand Phone: Fax: Email: Role: resourceProvider Position: Organisation: ASR Ltd Marine Consulting and Research Delivery Point: PO Box 67 City: Raglan Postal Code: Country: New Zealand Phone: 07 8250380 Fax: Email: enquiries@asrltd.co.nz Data Constraints Data Access Constraints : copyright Data Use Constraints: copyright Data Distribution: Unrestricted Licence Type : CC BY 4.0 Licence: https://creativecommons.org/licenses/by/4.0 Licence Expiry: Licence Conditions: WRC DOC# 1957708 Copyright : This work is licensed under a Creative Commons Attribution 4.0 International License © Waikato Regional Council & ASR Ltd Marine Consulting and Research. Bathymetry – Waihou River delta, Firth of Thames. Licensed under CC BY 4.0. Data Disclaimers : The standard Waikato Regional Council Disclaimer applies to this data “While Waikato Regional Council has exercised all reasonable skill and care in controlling the contents of this information, Waikato Regional Council accepts no liability in contract, tort or otherwise howsoever, for any loss, damage, injury or expense (whether direct, indirect or consequential) arising out of the provision of this information or its use by you.” Data Use Limits : Data was collected for hydrodynamic modelling, not for navigational purposes. Download Links URL Format Notes Supporting Information Links URL Format Notes General Notes: Attribute Information Name Description Notes Restricted Primary Key ID N Y