Datawell Waverider Reference Manual WR-SG DWR-MkIII DWR-G Datawell BV ocea nog raphic in s tru men ts Service V o l t a s t r a a t 3 1704 RP Heerhugowaard The Netherlands + 31 72 571 8219 + 31 72 571 2950 Sales Zomerluststraat 4 2012 LM Haarlem The Netherlands + 31 23 531 6053 + 31 23 531 1986 October 10, 2009 www.datawell.
Contents 1 Introduction ................................................................................................... 7 2 Maintenance................................................................................................... 9 2.1 Consumables ......................................................................................... 10 2.1.1 Logger............................................................................................. 10 2.1.2 Batteries......................................
5.3.4 Electronics unit................................................................................ 29 5.3.5 Hatchcover...................................................................................... 31 5.3.6 Antennae......................................................................................... 32 5.4 Wave motion sensors: Accelerometers, inclinometers and compass..... 34 5.4.1 Wave height, principle of measurement.......................................... 34 5.4.
.9.3 Mooring eye .................................................................................... 81 5.9.4 Fender ............................................................................................ 81 5.9.5 Anti-spin triangle ............................................................................. 81 5.9.6 Handles........................................................................................... 82 5.9.7 Flange, serial number and FS direction ......................................
5.17.11 Error messages......................................................................... 120 5.17.12 Copyright................................................................................... 121 5.18 Contacts and Questions ..................................................................... 122 5.18.1 Addresses ................................................................................... 122 5.18.2 Telephone and fax numbers ....................................................... 122 5.18.
1 Introduction After having set up your Datawell wave measuring equipment by following the steps in the Installation Guide, you probably have been collecting wave data for some time. At some point you ask yourself whether your equipment requires any maintenance. Chapter 2 Maintenance will answer your questions. While at sea or on land your equipment may not work without fault or may not work at all.
2 Maintenance During the life of your buoy it will require some maintenance even though it may function without error. For one thing, the buoy contains several consumables that must be replaced at regular time-intervals. Furthermore, by carefully inspecting some parts it may be possible to foresee problems and to take measures in advance. Every time you have the opportunity to do so, you should inspect the indicated parts. Finally, some regular maintenance remains.
2.1 Consumables 2.1.1 Logger Depending on the memory size typically the logger fills within four and a half months to two years. When full the logger will continue logging by selectively overwriting data (RDT-files, not SDT-files) using the smallest significant wave height as a selection criterion. To prevent this, a filled logger flash card should either be replaced or its contents moved timely. For example a 128 Mb logger flash card will store 4.
2.1.3 Sacrificial anodes Aluminium sacrificial anodes slowly dissolve in sea water thus protecting the stainless steel hull through a galvanic reaction. Cunifer10 hulls do not require anodes. Anodes will approximately last for three years, unless the buoys are located in warm (> 20 ºC) or polluted sea water. However, no guarantee can be given and the rate of anode material consumption must be established through timely inspections. 2.1.
2.2 Inspection 2.2.1 Mooring Bent terminals in the mooring line may indicate extreme forces. Verify with Datawell whether your mooring is suitable for your local conditions before you redeploy the buoy at the same location. Inspection of the rubber cords and the polypropylene line may show signs of wear. Make use of these early warning signals and think what may be the cause (e.g. rocky bottom) before you redeploy. In section 5.8 on the mooring you will find further suggestions. 2.2.
2.3 Service 2.3.1 WR-SG and DWR-MkIII wave motion sensor The stabilized platform vertical accelerometer consists of a fluid-filled sphere. Over the years the fluid evaporates through the Perspex sphere. Check the fluid level at least once every three years. Experience has it that a small refill is required every three years. Section 5.4 will explain where to check and how to refill.
3 Trouble Shooting So far faultless buoy behaviour with regular maintenance only has been assumed. This chapter will deal with minor problems that may be traced and solved by you yourselves. The easiest way to diagnose buoy problems is to query the onboard microcomputer. It will help you to identify the problem and check if the electronics unit works fine. Still the real problem may lay further down or up with the electronics module of the malfunctioning sensor or communication means.
3.3.2 Magnetic compass The inclination and orientation angles of the DWR-MkIII are presented after a status request. Inclination is the angle the local earth magnetic field makes with the local earth surface. A measured inclination angle which matches the true local inclination within 1.5º indicates that (1) the compass is functioning well, and (2) the offset angle of the platform is not too large. Local inclination may be found on the web, e.g. visit www.ngdc.noaa.gov/seg/potfld/geomag.html.
3.6 LED flashlight Covering the LED flasher at the top of the HF antenna, for at least 20 secs, will set it flashing for 15 cycles (approx. 5 min.). If the LEDs don’t flash, check the connectors and the coaxial cable below the option port labelled HF. You may also test the HF/LED antenna separately by applying 7.5 V over the connector at the base, positive voltage on the centre pin connector. Make sure the current does not exceed the 100 mA limit.
4 Repair Datawell recommends you send your buoy for service and maintenance every 3 to 6 years approximately. Also if your buoy does not function correctly and, although you may have tracked down the problem with help of the Trouble shooting chapter, you are not able to solve the problem, the malfunctioning buoy (part) should be send to Datawell Service. This chapter will explain where to turn for help and what information must be provided that Datawell may swiftly remedy your problems. 4.
4.4 Serial numbers If you have any questions regarding your buoy or if you encounter problems and you wish to contact Datawell, please keep the following serial numbers at hand. The most important numbers are the overall hatchcover assembly number and the overall hull assembly number. The former is located on the top centre of the hatchcover in the middle of the option ports, e.g. DWR-G 44014 or DWR-MkIII 43015.
5 Reference This is the largest chapter by far. All buoy functions and buoy parts will be discussed here. To start with, the various components of the buoy, their names and location will be introduced. You will be guided through: mooring, packing frame, hull, electronics unit, hatchcover and port options, first in general, then in detail. After that all possible standard functions and additional options will follow. Topics like internal data processing and buoy deployment procedure are also included.
5.1 Dangers and warnings Datawell distinguishes dangers, threatening your life and warnings, threatening your equipment. Below you find a summary of dangers and warnings related to the present product. 5.1.1 Dangers • Never deploy the anchor weight first, always deploy the buoy first followed by the mooring line, and finally deploy the anchor weight. • Never stand within loops in the mooring line, never stand between mooring and the ship board. Lines may pull you overboard.
5.2 Measuring waves with Datawell buoys 5.2.1 Wave height Waves at sea are the result of orbital motions of the water particles, characterized by their frequency f, amplitude A and direction. The water forces at the hull of the buoy cause a mass equal to the displaced water volume to follow the orbital motion. Since the mass of the buoy m equals the mass of the displaced water volume, the buoy will follow the orbital motion as well. Measuring the vertical motion of the buoy yields the wave height.
5.3 Buoy parts and options This section presents an overview of the components of your wave measuring system and their location. It is subdivided into six parts from the anchor weight on the sea bottom up to the HF antenna top. Except for the packing frame all subdivisions are rendered in Figure 5.3.1. Only a brief description is given in the following subsections, for details read the respective section in this chapter. Figure 5.3.1. Rendering of the components of a wave buoy system.
5.3.1 Mooring This subsection with figure only deals with mooring parts and naming-conventions. For the appropriate mooring layout in your local conditions see section 5.8. Figure 5.3.2 depicts the constituent parts of the mooring. The mooring starts with an anchor weight, preferably scrap chain, followed by a polypropylene (PP) rope. The first few metres of PP rope keep clear of the seabed by a small (3 Kg) inline float. The PP rope is connected to a rubber cord.
Figure 5.3.2. Constituting pieces of the mooring. Refer to section 5.8 for exact mooring design.
5.3.2 Packing frame For protection and handling the buoy should always be shipped in a packing frame. The packing frame holds the complete buoy and the stabilizing chain including anodes (anodes only on stainless steel buoys). Small option inserts, such as the GPS antenna, Argos and Orbcomm antennas, are packed in the hull during transport. Only the long HF/LED whip antenna and the anti-spin triangle must be packed separately for transport. Figure 5.3.3 depicts the packing frame with a buoy in it.
Figure 5.3.4. Rendering of the hull components, 0.9 m diameter. (a) shows the exterior and (b) the interior.
Figure 5.3.5. Contents of the aluminium can in case of (a) a WR-SG and (b) a DWR-MkIII So far the contents of the aluminium can has not been described. In the WR-SG and DWR-MkIII 0.9 m and 0.7 m diameter, Figure 5.3.5(a) and (b), the can houses the motion sensor package and water temperature sensor (optional on WR-SG) at the bottom and partly inside the mooring eye.
Figure 5.3.6. Schematic drawing of the printed circuit boards on the inside of the electronics unit and the connector block in the middle Figure 5.3.7.
5.3.5 Hatchcover Two hatchcover versions exist: one with two and one with three ports. These ports are designated HF (whip antenna with LED flasher), GPS (GPS antenna for GPS position on WRSG and DWR-MkIII and GPS wave measurement on DWR-G alike) and, in case of three ports, the third port (optional) is designated Orbcomm, Argos, Iridium or GSM, consistent with prefixed cabling below. All ports require a rubber sealing ring for waterproof sealing.
Figure 5.3.9. Opening the hatchcover by using a screw in the lifting hole. 5.3.6 Antennae The antennae are also part of the modular design of the WR-SG, DWR-MkIII and DWR-G. Not only will it be possible to replace antennae with upgraded versions, but you may also extend buoy functionality with future options that are not even perceived yet. Figure 5.3.10 shows the antennae that are currently available. Mounting an antenna on a port is straightforward. Make sure antenna and port are clean and dry.
Figure 5.3.10.Different types of antennae: HF whip including LED flasher(a), LED flasher only whip(b), GPS wave(c), Orbcomm(d), GPS position(yellow)(e), Argos(f) Iridium(blue)(g), GSM(h). Figure 5.3.11. Illustration of how to fix an antenna or sensor option to a port. Please make sure the rubber sealing ring is in place.
5.4 Wave motion sensors: Accelerometers, inclinometers and compass 5.4.1 Wave height, principle of measurement The WR-SG and DWR-MkIII measure wave height by means of a single accelerometer. The sensitive axis of this accelerometer points in the vertical direction. After filtering and double integration of the acceleration signal the motion of the buoy, hence the wave motion, is obtained. The strength of the Datawell principle is its gravity-stabilized platform.
Figure 5.4.1. Definition of the axes and signs of the DWR-MkIII motion sensors. 5.4.4 Inspection of the fluid level As mentioned in Chapter 2 Maintenance it is important for the stabilized platform and vertical accelerometer sensor to periodically check the fluid level within the plastic sphere. The fluid level can be visually inspected through the Perspex lid on the sphere, see Figure 5.4.2. If the centre of the rubber membrane is pointing upwards, Figure 5.4.2(b), the fluid level is sufficient.
Figure 5.4.2. Examples of the fluid level of the stabilized platform and vertical accelerometer sensor: (a) fluid level too low, (b) fluid level sufficient. 5.4.5 Sensor fluid and temperature It has been written repeatedly that the accelerometer based buoy must not be stored below temperatures of −5 ºC. This is determined by the freezing temperature of the fluid surrounding the stabilized platform.
5.4.6 Calibration of the vertical accelerometer A calibrated vertical accelerometer and stabilized platform should perform within limits over 3 to 6 years, depending on operating conditions. Consequently Datawell recommends recalibration of your buoy every 3 to 6 years. To eliminate any doubt about the calibration, the following tests may be carried out. To test the vertical accelerometer, the buoy must be set in motion first.
5.4.8 Magnetic compass The fluxgate compass measures the components of the earth magnetic field in three perpendicular directions referenced to the buoy frame: x-, y- and z-axis. The compass consists of an aluminium cube with three holes in three mutually perpendicular directions. In each hole a magnetic field sensor is placed. This part requires extremely little service. Before any checks can be carried out we must make sure that the local magnetic field is stable and homogeneous.
5.4.12 Specifications For the non-directional Waverider (WR-SG) see Table 5.4.3 and for the Directional Waverider MkIII (DWR-MkIII) see Table 5.4.4. Table 5.4.3. Specifications of WR-SG. Value Parameter Heave Range Resolution Scale accuracy (gain error) Zero offset Period time Cross sensitivity −20-+20 m 1 cm < 0.5 % of measured value after calibration < 1.0 % of measured value after 3 year < 0.1 m 1 s-24 s < 3% Filter Sampling frequency Digital filtering type 10.
Table 5.4.4. Specifications of DWR-MkIII. Parameter Value Heave Range −20-+20 m Resolution 1 cm Scale accuracy (gain error) < 0.5 % of measured value after calibration < 1.0 % of measured value after 3 year Zero offset < 0.1 m Period time 1.6 s-30 s Cross sensitivity < 3% Direction Range 0º-360º Resolution 1.5º Reference magnetic north Buoy heading error 0.4º-2º depending on latitude, typical 0.5º Period time in free floating condition 1.6 s-30 s Period time in moored condition 1.
5.5 Wave motion sensor: GPS 5.5.1 Wave measurement principle The GPS principle of wave measurement is explained by analogy. Apart from distance measurements between satellite and receiver, the so called GPS code phase, some GPS receivers also provide Doppler measurements. The former are used in GPS positioning, whereas the latter are indicative of satellite and receiver velocities. Now, we exploit the analogy of Doppler frequency shifts for sound waves from moving sources.
5.5.6 Selective availability As mentioned the GPS system originally was and still is a military system, maintained by the United States Department of Defence. As such a few features are incorporated to restrict the use of precise GPS to selected users. This is known as Selective Availability (SA). When SA is active a dither is added to the satellite GPS time thereby deteriorating the GPS position accuracy from 10 m to 100 m. Furthermore the precision of the satellite orbit information may be reduced.
5.6 Data processing Independent of the type of sensor, the DWR-MkIII and DWR-G generate raw north, west and vertical displacements at a rate of 1.28 Hz. The WR-SG however generates vertical displacements at 2.56 Hz. Displacements refer to excursions from the average position and should not be mistaken for position changes relative to the previous position. The raw data is stored on the logger flash card and output through the radio link.
The power spectral density is obtained from the Fourier coefficients PSD( f 0 ) = H 0 2 PSD( f l ) = H l 2 (5.6.5a) + H N −l PSD( f N / 2 ) = H N / 2 2 l = 1K N / 2 − 1 2 (5.6.5b) (5.6.5c) where frequencies range from 0.0 Hz to 0.64 Hz in steps of 0.005 Hz. Actually, there is one more step, all coefficients are smoothed according to PSDl = 1 1 1 PSDl −1 + PSDl + PSDl +1 4 2 4 (5.6.6) To limit the number of frequencies low frequency coefficients (fl ≤ 0.
Thus, one obtains: ⎛ C ww ⎜ ⎜ C nw ⎜C ⎝ vw C wn ⎛ 0 ⎜ ⎜ 0 ⎜Q ⎝ vw 0 C nn C vn C wv ⎞ ⎟ C nv ⎟ C vv ⎟⎠ (5.6.12) and 0 Qvn Qwv ⎞ ⎟ Qnv ⎟ 0 ⎟⎠ (5.6.13) Given these components a whole set of informative wave parameters such as: wave direction, direction spread, wave ellipticity can be obtained. Before discussing their meaning in more detail, first, all formulas will be given. a1 = Qnv (C nn + C ww )C vv (5.6.14) b1 = − Qwv (C nn + C ww )C vv (5.6.15) a2 = Cnn − Cww Cnn + Cww (5.6.
Wave direction D = θ 0 = arctan (−Qwv , Qnv ) (5.6.24) Directional spread S = 2 − 2m1 (5.6.25) Wave ellipticity or 1/K where K is the check factor ε = 1/ K = C vv C nn + C ww (5.6.26) Power Spectral Density PSD = C vv (5.6.27) In the present context parameters ai and bi are just helpful intermediate variables. In terms of this more intricate Fourier analysis we again arrive at the power spectral density. Its value and meaning already have been mentioned.
5.7 Data format Datawell uses two types of message formats: the real-time format and the message format. The Datawell real-time format refers to the long-existing hexadecimal vectors with vertical, north and west displacements and words ultimately forming the spectrum and system files. It is mainly used for relatively low-speed, continuous, near real-time data transmission over the standard HF radio link. More recently, the Datawell message format has been introduced.
5.7.1.2 Spectrum file or full wave spectrum One level further up the cyclic data contained within 18 vectors forms one block. The cyclical data is organized as shown in Table 5.7.2. One block provides information on spectral parameters at 4 frequencies. The parameters are: • • • • • • frequency f relative power spectral density RPSD K check factor (reciprocal of the wave ellipticity) mean direction from D direction spread S centred Fourier coefficients (m2 and n2), see Equations (5.6.22) and (5.6.23).
Table 5.7.3. Translation equations for spectral parameters in spectrum file. Parameter Equation Remarks Frequency fn = 0.025 Hz + nΔf Δf = 0.005 Hz, n = 0…15 fn = 0.11 Hz + (n−16)Δf Δf = 0.01 Hz, n = 16…63 Direction D = D 360º/256 0º = north, 90º = east Relative power RPSD = exp(−RPSD/200) max 1, multiply by power spectral density density in system file Spread S = 0.
Table 5.7.4. Organization and significance of the system file data.
5.7.1.5 Compressed wave spectrum The wave spectrum computed internally by the buoy covers 128 frequency bands and is condensed to 64 frequency bands occupying 512 bytes (spectrum file, full wave spectrum). To save bits while maintaining a large range of values an exponential representation of numbers is used. Furthermore, the initial 64 frequency bands of the full spectrum are reduced to 13 bands.
Table 5.7.7 gives the formulas to restore the original parameters from the compressed representation in the 32 byte message. The 32 bytes are organized as 16 words with the most significant byte first. Table 5.7.7. Compressed wave spectrum back-transformation equations. Parameter Formula Unit Remarks Total variance m0 m range 8.3 m ⎡ ⎛ M0⎞ ⎤ m 0 . 16 exp 1 − = ⎟ ⎜ (integrated PSD) min. res. 0.51 cm 0 ⎢ ⎥ ⎣ ⎝ 32 ⎠ ⎦ rel. res. 3.2% Frequency upper Hz ⎡ ⎛F⎞ ⎤ f = 0.04⎢exp⎜ ⎟ − 1⎥ + 0.
5.7.2 Datawell message format As any message-type format the Datawell message format brings about a high degree of flexibility. In addition, the Datawell message format incorporates two compression methods: • • transformation of real numbers to integers, and smart decimation As a result also compact messages for low-capacity, high-cost datalinks such as satellite communication are possible. This subsection starts with the format, listing and discussion of the currently defined messages.
5.7.2.2 CRC-4 checksum computation The CRC-4 is a cyclic redundancy check, where the 4 indicates the number of bits in the CRC checksum. Every message m can be considered as a string of n bits bj: m = bn−1 b n−2 b n−3 … b1 b0 (5.7.1) where every bj is either 0 or 1. To this message m we add four bits that are zero: m’ = bn−1 b n−2 b n−3 … b1 b0 0 0 0 0 (5.7.2) This bit string can be interpreted as a binary polynomial: m’(x) = b n−1xn+3 + b n−2xn+2 + b n−3xn+1 + … b1x5 + b0x4 (5.7.
/*This is the key table for CRC generator X^4+X+1*/ const unsigned char keytable[16]={0,3,6,5,12,15,10,9,11,8,13,14,7,4,1,2}; /*This routine checks the crc of a message The routine uses a precalculated table must point to the message to be checked is the number of bytes in the message If returned crc=0, message is OK*/ unsigned char ChkCrcCode (unsigned char *data, unsigned char n) { unsigned char i,crc; crc=0; for(i=0;i>4))&0x0f]; /*first
5.7.2.4 Spectral parameters (MsgID = 3) Table 5.7.12 explains the "Spectral parameters" message. The periods T(n,n+1) := mn/mn+1 and T(n,n+2) := √(mn/mn+2) are computed from the moments mn of the spectrum. mn = ∫ df f n S ( f ) (5.7.9) In addition, Tdw and Goda’s peakedness parameter Qp are included: 1 df f −1 S 2 ( f ) ∫ m0 2 Q p = 2 ∫ df f S 2 ( f ) m0 Tdw = (5.7.10) (5.7.11) plus the peak period Tp, defined through S(1/Tp) = Smax. See also Table 5.7.17.
Table 5.7.13. Buoy information message (MsgID = 5). Byte HiNibble LoNibble 0 MsgID = 5 = 0101 CRC-4 checksum 1 GPS Latitude 2 3 4 GPS Longitude 5 6 7 8 9 Battery Status Av Ay Ax (Reserved) 5.7.2.6 Meteorological parameters (MsgID = 6) Table 5.7.14 explains the "Meteorological parameters" message. The water temperature Tw is a 10-bit number, scaled linearly: Tw = i/20 −5 in units of °C. Table 5.7.14. Meteorological parameters message (MsgID = 6).
frequencies as the heave spectrum. In the even bins (0, 2, 4, …, 26), the direction is given as a 8-bit integer: Dir = i *360 / 256 (5.7.17) which results in a 1.4° accuracy. In the odd bins (1, 3, 5, …, 25), the directional step with respect to the previous direction is given. For these delta-directions ΔDir, a 4 bit two’scomplement is used as explained in Table 5.7.16. i 0000 0001 0010 0011 Table 5.7.16. Two's-complement representation of ΔDir.
This transformation has an additional parameter b. For very large values of b (b → ∞) the transformation becomes linear, r / rmax ≈ i / imax. For small values of b, it becomes exponential, r ≈ rmax exp(-imax / b) exp(i / b). The resolution of the r values is found to be: Δr = ri +1 − ri = r1 + ri ⋅ (e1 / b − 1) ≈ r1 + ri / b (5.7.24) which means that there is an absolute accuracy of r1 and a relative accuracy of 1/b. Example: Let r be a wave height in cm.
The decimation is hence a list of 27 indices, k0(kmax)…k26(kmax), of the bins that are included, and since the list depends on kmax, it can be tabulated in a 112×27 matrix, k kmax ,l = kl(kmax) (5.7.25) There will of course always be a l for which k kmax ,l = kmax, i.e. the bin of the spectral peak is always included. The same holds for the adjacent bins. As an example, let us assume that the spectral peak is at a frequency of 0.25 Hz, i.e. kmax = 50. Then: k13(50) = k50,13 = 50 (5.7.
Table 5.7.18. Frequency bins of compressed spectra after smart decimation. fp 0.025 0.030 0.035 0.040 0.045 0.050 0.055 0.060 0.065 0.070 0.075 0.080 0.085 0.090 0.095 0.100 0.105 0.110 0.115 0.120 0.125 0.130 0.135 0.140 0.145 0.150 0.155 0.160 0.165 0.170 0.175 0.180 0.185 0.190 0.195 0.200 0.205 0.210 0.215 0.
fp 0.225 0.230 0.235 0.240 0.245 0.250 0.255 0.260 0.265 0.270 0.275 0.280 0.285 0.290 0.295 0.300 0.305 0.310 0.315 0.320 0.325 0.330 0.335 0.340 0.345 0.350 0.355 0.360 0.365 0.370 0.375 0.380 0.385 0.390 0.395 0.400 0.405 0.410 0.415 0.420 0.
fp 0.430 0.435 0.440 0.445 0.450 0.455 0.460 0.465 0.470 0.475 0.480 0.485 0.490 0.495 0.500 0.505 0.510 0.515 0.520 0.525 0.530 0.535 0.540 0.545 0.550 0.555 0.560 0.565 0.570 0.575 0.
5.8 Mooring The correct mooring of a wave buoy is essential to measuring wave parameters according to specifications, see also section 5.2. The design of an appropriate mooring requires knowledge of the current speed and profile, the depth, tides, wave height and sometimes the seabed structure. To help our customers in finding a good mooring solution, Datawell has developed a standard mooring lay-out that applies to a wide range of situations.
5.8.4 Polypropylene (PP) rope Datawell supplies synthetic fibre 12 mm multiplaited polypropylene rope, in short polypropylene (PP) rope. PP-rope is torsion free and has a breaking strength of 2000 Kg. It is delivered on coils (200 and 500 m). Coils of rope should be unrolled. Pull in the direction of the tangent rope (tangentially). Never pull a length of rope from the coil in the direction of the axis of rotation (axially). Doing so will result a line impossible to handle due to the torsion built up.
5.8.5 Sinker For larger depths, Datawell provides in-line sinkers which avoid the polypropylene line coming afloat. The sinker consists of two identical aluminium parts which can be fitted to the 12 mm multiplaited polypropylene rope supplied by Datawell. Applying or removing the sinkers from the rope can be done without special equipment or small parts. See figure 5.8.3. Press to lock Figure 5.8.3. Aluminium sinker consisting of two identical parts.
5.8.6 Floats The purpose of floats is to keep the mooring free from the seabed. Datawell provides two types of floats, a 3 Kg and a 10 Kg float. The 0.2 m diameter, 3 Kg buoyancy float can be tied with a 8 mm nylon rope to the polypropylene rope by two times a clove hitch, see Figure 5.8.4. This way of mounting is called in-line float and it leaves the main rope intact. In this way the strength of the polypropylene rope is not decreased.
5.8.8 Chain coupling and swivel The Waverider buoys are fitted with a 5 Kg chain coupling attached to the mooring eye. This provides stability when only a small vertical mooring force is present, e.g. for a free floating buoy or a buoy moored in shallow water. Without chain coupling and when broken adrift, large pitch and roll amplitudes could cause irreparable damage to the stabilized platform.
5.8.9 Anodes Corrosion risks of the stainless steel AISI316 buoy hull can be prevented by applying sacrificial aluminium anodes. These anodes can be fitted to the chain below the buoy (from the second link from the buoy). In the water an adequate galvanic current path is formed between the anodes and the hull through the chain and back through the sea water. The layout of the protective anodes is given in Figure 5.8.6. At least one free link should be left between the clamps and the buoy.
5.8.10 Standard mooring layout Mooring packages are available for each range of depth. All components are of high quality to prevent corrosion, and kinking and twisting of the mooring line. Shackles and terminals for easy mounting are included.
Figure 5.8.7(a) Mooringline layout for the (Directional) Waverider.
Figure 5.8.7(b) Mooringline layout for the (Directional) Waverider.
Figure 5.8.7(c) Mooringline layout for the (Directional) Waverider.
Figure 5.8.7(d) Mooringline layout for the (Directional) Waverider.
Figure 5.8.7(e) Mooringline layout for the (Directional) Waverider.
5.8.11 Applicability of the standard mooring layout In Table 5.8.2 below, it is indicated up to what depth the standard mooring applies. If the local current strength corresponds to the entry in the first column, then the depth in the second column in the same row is the maximum depth up to which the standard mooring applies. The current is assumed to extend over the full depth. Table 5.8.2. Applicability of the standard mooring layout. Current speed (m/s) Max. depth Max. depth 0.7 m buoy 0.9 m buoy 0.
anchor weight, either a ship with a hoisting crane or U-frame or a ship with a removable railing should be chartered. For comfortable deployment a day with small waves is best waited for. The procedure in Figure 5.8.8 is suggested for a small vessel with a hoisting crane or removable railing in the front. Users should adapt the procedure to size and outfit of their ship and according to their own experience.
5.8.14 Recovery IMPORTANT – During the recovery process the most dangerous item is the rubber cord(s). Stretching the cord(s) increases the level of danger and should be avoided whenever possible. There are several techniques for recovering a Waverider buoy. The most suitable method on any particular occasion will depend on the location, the weather, the sea state, the type/size of vessel being used, the availability of substitute equipment and, sometimes, operator experience/preference.
5.8.15 Mooring hazards The phenomenon most likely to result in early failure of the mooring is galvanic corrosion between different metals in sea water. When a mild steel shackle is coupled to the AISI316 stainless steel Waverider the shackle may fall apart within one month. Even the coupling of AISI304 and AISI316 stainless steel will lead to early failure. In case it is necessary to couple different metals, an electrically insulating element should be used.
5.9 Hull and hatchcover Hull and hatchcover form a watertight compartment that provides buoyancy and houses batteries, sensors and electronics. This section only describes all items on the exterior and some basic functions in the interior of the compartment. Separate sections are devoted to battery compartments, electronics unit, motion sensors and temperature sensor. 5.9.1 Packing frame and buoy weights For safe transportation the buoy must be packed in the packing frame in which it arrived originally.
drag. As alternative to anti-fouling paint we supply buoys with a Cunifer10 hull. Cunifer 10 is a copper-nickel alloy which does not pit and reduces fouling. Paint may be applied on a AISI316 hull for protection against pitting, better visibility or because of navigation regulations. For painting we recommend the Brantho Korrux “3 in 1” (RAL 1023) paint system which has proven its quality in a maritime environment.
Figure 5.9.1. Anti-spin triangle mounting on a Waverider buoy. 5.9.6 Handles When lifting or moving the buoy you can use the two handles welded onto the hull top side. Two handles must be used to carry the load of the whole buoy. The DWR-G buoy is fitted with a hauling rope between the two handles as a standard. 5.9.7 Flange, serial number and FS direction Through the flange the interior of the buoy can be accessed. Almost all parts within the hull can be serviced or even replaced through this flange.
paper bag back into the plastic bag. To prevent unnecessary moisture saturation of the drying agent, close the hatch whenever the buoy is not in use. The bags are fixed to the plywood boards with Velcro straps. Four plywood boards hold down the batteries in the outer ring and the aluminium lid on the aluminium can or the batteries inside the can. To hold down the batteries inside a plywood disk with four legs is used. Fold the disk and unscrew some legs if you need to take it out. 5.9.
Figure 5.9.2. (a) Top and (b) bottom side of the hatchcover.
5.9.11 Radar reflectors Radar reflectors are available for the DWR MkIII, DWR-G and Waverider SG buoys with a 475 mm hatchcover. Two radar reflectors can be fitted on the hatchcover in order to gain an omnidirectional radar reflecting system. This radar reflecting system doubles the buoys visibility on a 3 GHz radar while on a 10 GHz radar the buoy will be ten times better visible. The radar reflectors are made from corrosion resistant stainless steel.
The rechargeable cell requires a recharger. Please check the manual of the recharger for optimal use of the rechargeable cells. In short: keep the cells fully charged as much as possible. 5.10.2 Battery status With help of Table 5.10.3 the battery status bits may be translated into weeks left before the buoy runs out of energy. There are two methods to determine the remaining operational life. One is to measure the voltage and to relate this to the battery discharge curve.
Figure 5.10.1. Solar panel array with cells linked in series (A, left) or in matrix (B, right). During even reasonably short deployments, surface floating buoys such as the Waverider cannot avoid suffering from marine growth, salt crystals, bird deposits and physical knocks. Shadows cast by the antennae and fixings will also intrude between the sun and the solar cells. Therefore, a novel cell configuration has been used to deal with these situations.
5.10.4 Battery replacement and wiring The batteries are organized, first in series of several cells and second in several series in parallel. In Table 5.10.4 the number of batteries per series and the number of series in parallel are given for the various buoy models. Table 5.10.4. Battery type, organization and total number of batteries and total energy content per buoy model. Buoy model Battery type Cells per Series in Total Total energy series parallel number content (Wh) WR-SG 0.
Figure 5.10.2. Battery numbering, wiring and grouping for a 0.
Figure 5.10.3. Battery numbering, wiring and grouping for a 0.
Figure 5.10.4. Battery wiring for a 0.7 m diameter DWR-MkIII.
Figure 5.10.5. Battery numbering, wiring and grouping for a 0.
Figure 5.10.6. Battery numbering, wiring and grouping for a 0.
Figure 5.10.7. Battery numbering, wiring and grouping for a 0.
Figure 5.10.8. Battery wiring for a 0.
Figure 5.10.9. Battery wiring for a 0.
5.10.5 Power consumption and operational life The power consumption meter provides the remaining operational life of the buoy. Over time the reading will provide a more precise estimate of the power consumption in your particular conditions. Given the power consumption and the energy content in the previous subsection, you may calculate the operational life of your buoy, see Table 5.10.5. Table 5.10.5.
5.11 Electronics unit Apart from some distributed sensor electronics all electronics is concentrated in the electronics unit. The unit is located below the hatchcover. It features a modular design that allows adding and/or upgrading of existing and future sensor and communication options electronics. A Cprogrammable microprocessor forms the heart of the electronics unit and in fact the whole buoy.
Figure 5.11.1. Drawing of the connector block, in the middle, and the printed circuit boards on the inside of the electronics unit. Figure 5.11.2. Drawing of the cylindrical shaped electronics unit of 0.4m DWR-G4. (a) shows schematically depicts the interior and (b) the side panel.
5.11.2 Electronic modules on the inside For access to the printed circuit boards the electronics unit must be dismantled. After unscrewing the three removable feet, the aluminium cover can be removed. Figure 5.11.1 and 5.11.2 (b) schematically shows the location of the boards. The microprocessor, power supply, GPS receiver, high frequency radio link and LED flasher control are all incorporated on the main board (except DWR-G4). The data logger is directly under the connector block of the electronics unit.
To set up the console connect a serial cable to the 9-pin female plug on the electronics unit and to your terminal or PC. The terminal or terminal-emulation program and serial port should be configured as follows: • • • • • • • Line feeds should be added to incoming carriage returns. Local echo should be turned off. Terminal mode is not critical, as the console uses no special formatting. RS232 interface 9600 baud 8 data bits, 1 start bit, 1 stop bit no parity, no flow control 5.11.
Table 5.11.1. Overview of buoy commands in alphabetical order. x indicates availability for the particular buoy model. Command WR- DWR- DWR- Meaning SG MkIII G checksum x x x request firmware checksum forcefix x x force GPS module to find new position fix initorb x x x simulates a default user command to start Orbcomm module without satellite intervention (if Orbcomm option is installed).
5.11.6 Messages As mentioned the buoy will generate messages autonomously and in response to user commands. Table 5.11.2 lists all messages that may appear in normal mode. In verbose mode additional messages will appear, these are not listed in this manual. Table 5.11.2. Overview of buoy messages in normal mode in alphabetical order.
5.12 Logger All buoys are equipped with an internal data logger as a standard. Raw displacements measurements, wave spectra and system files generated in the buoy are all logged without any loss of data. In times of disturbed HF transmission or when, for the moment, you only receive compressed wave spectra through satellite, you may rest assured that the full set of data is secured on the logger. To diagnose buoy (dis-)functioning during testing or deployment also a specific set of events are logged.
5.12.3 Retrieving logger files Before removing the flash card or even removing the power it is important that the logger is stopped. To stop the logger, use the console command stoplog. Refer to the chapter on the console for more information. The LED light next to the flashcard insert lights up when writing actions take place on the card. Now the power may be disconnected and the flash card ejected.
Table 5.12.1. Logger memory size and data capacity. Flash card size Spectra capacity Displacements (MB) (months) capacity (months) 128 36 4.7 256 36 11* 512 36 24* 1024 36 49* 2048 36 100* *displacement files may contain multiple days per file 5.12.5 Raw displacements file These files are identified by the RDT suffix. Initially, one file contains 48 displacement data messages of half an hour each, covering one single day.
5.12.7 Event log file This file is always named HISTORY.DOC. Note that this is a human readable text file that does not contain messages. In order to trace buoy behaviour during testing or deployment several events are logged. Table 5.12.2 gives a list of all possible events. In case you experience any buoy problems and you intend to contact Datawell Service please include this log file in your email or keep it at hand when calling. Table 5.12.2.
5.13 GPS position With GPS (Global Positioning System) and HF communication the position of a drifting buoy, be it on purpose or accidentally, can be tracked. GPS is standard on all buoys. Latitude and longitude are updated once every half hour and transmitted to the user 8 times in one half hour. The position accuracy is about 10 m (0.3”). Position integrity is monitored by the GPS receiver. Only if the receiver flags the position as valid, will the position be updated and transmitted.
5.14 Water temperature A water temperature sensor is standard on the DWR-MkIII buoy models and optional on all other buoy models. The sensor is located in a pocket in the interior of the mooring eye in direct contact with the metal. In this way influences of the warmer topmost water layer and heat conduction from the sun lit top half of the buoy are minimized. Even the effect of marine growth is small due to the large contact area of the bottom half of the hull.
5.15 LED flashlight Both to the well-being of seafarers and the buoy, Datawell buoys are equipped with a flash light as a standard. The colour and flash pattern, group of 5 yellow flashes every 20 seconds, comply with regulations for Ocean Data Acquisition Systems (ODAS) in the International Association of Lighthouse Authorities (IALA) buoyage system A. The visibility range amounts to 4 nautical miles (Nm) under standard atmospheric conditions.
5.16 HF communication The default way of communicating the wave data to the shore is through HF communication. Each buoy transmits at its own frequency, thus allowing several wave measurement buoys in the same area at sea. A large set of frequencies in the range 27-40 MHz is available. The transmitting range extends to beyond line-of-sight and amounts to some 50 Km. Data are transmitted continuously by Frequency Shift Keying (FSK) at a rate of 81.92 baud. Please refer to the data format section 5.
Figure 5.16.1. HF whip antenna insert with LED flasher.
5.17 Iridium satellite communication Iridium is a satellite based cellular phone network. It is built upon a constellation of 66 low earth orbit (LEO) satellites. The constellation is organized in such a way that every part of the globe is covered 24 hrs a day. Iridium gets its name from the element Iridium (Ir), which has an atomic number of 77. This name was chosen because the constellation would initially be built upon 77 satellites.
5.17.4 PIN-code In order for the Iridium option to function, the SIM-card has to be in unprotected mode: a mode where the SIM-card does not require a PIN- or PUK-code. Please indicate this to the Iridium provider when ordering a SIM-card. The provider should be able to deliver an unprotected SIMcard. If the SIM-card is not in unprotected mode, the PIN-code has to be removed manually. This is possible using a special configuration sequence, see section 5.17. 5.17.
5.17.8 Buoy configuration A menu is provided to enter all buoy settings. The menu is invoked by the “settcp” console command, see figure 5.17.1. ***TCP/IP menu*** 1 dial1=d10sAT&F#~sAT+CBST=6,0,1#~sAT+CSQ#~w10:5~sATD69831676012321#~w60CONNECT~pkpn,~ 2 dial2=d10sAT&F#~sAT+CBST=6,0,1#~sAT+CSQ#~w10:5~sATD69831676012321#~w60CONNECT~pkpn,~ 3 addr1=81.4.80.140 4 port1=1168 5 addr2=81.4.80.140 6 port2=1168 7 id =bob the buoy 8 int =1 9 exit > Figure 5.17.
d10sAT&F#~sAT+CBST=6,0,1#~sAT+CSQ#~w10:5~sATD#~w60CONNECT~ p,~ This is the default Iridium dial script used to connect to a normal ISP. is the full (international) dial-in number of the provider and and are the account’s user name and password respectively. d10sAT&F#~sATD#~w60CONNECT~p,~ This is the default GSM dial script used to connect to a normal ISP.
5.17.8.5 Backup scripts and addresses The backup versions of the dial script and host address settings are very important because the buoy always takes the initiative when setting up a communication session.
Figure 5.17.4a Figure 5.17.4b command sequences that should cater for most situations. For more detailed information please refer to the Datawell technical note library. Command Creset Cdirec Crfile Cstore rbyid4 rtspc3 rcs001 rns001 rcs1 witxi2= wfnme4=”” wflen2= wfoff2= 118 Table 5.17.1. Buoy commands Description Reset buoy Read logger directory Read a file from the logger. The name, offset and length of the file must be set by writing the corresponding parameters first.
5.17.10.2 Default command examples Here follow some example default command sequences Downloading of current full wave spectrum This sequence will download the current full spectra and save it as an .SDT file. Only the current full spectrum can be downloaded. This list can be used with any transmission interval.
wfnme4=”S05-2006.SDT” wflen2=26400 wfoff2=475200 crfile (file with spectral data of may 2006) (length = 48 spectra of 550 bytes) (offset = 18 days * 48 spectra of 550 bytes) (read actual data) Downloading history.doc from the logger This sequence will download the history file “history.doc” from the internal logger. It is assumed that the file is less than 99999 bytes long (for longer files, wflen2 may be increased or only the last few kilobytes of the file may be downloaded). wfnme4=”HISTORY.
5.17.12 Copyright The Datawell internet communication module uses the UIP TCP/IP stack. Copyright (c) 20012006, Adam Dunkels and the Swedish Institute of Computer Science All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2.
5.18 Contacts and Questions For brochures, quotations and orders please contact Datawell Sales. For technical questions, support, training and advice contact Datawell Service. 5.18.1 Addresses Please mail documents to Buoys and parts should be shipped to Sales Datawell BV Zomerluststraat 4 2012 LM Haarlem The Netherlands Service Datawell BV Voltastraat 3 1704 RP Heerhugowaard The Netherlands 5.18.
5.19 Literature [Long63] Longuet-Higgins M.S., Cartwright D.E., Smith N.D., Observation of the directional spectrum of sea waves using the motions of a floating buoy, in Ocean wave spectra, Prentice-Hall, 1963, pp 111-136. [Rad93] Rademakers P.J., Waverider-wavestaff comparison, Ocean Engineering, vol 20, no 2, pp 187-193. [Tuck01] Tucker M.J., Pitt E.G., Waves in ocean engineering, Elsevier ocean engineering book series, vol 5, Elsevier, 2001. [Kuik88] Kuik A.J., Vledder G.Ph. van, Holthuijsen L.H.
