An eventful travel to the fabled Kingdome of Saudi Arabia...!!!

It is not my first trip to the Kingdome but as destiny would have it, happened to be an eventful one. Having received a couple of calls to join projects elsewhere in the gulf, I insisted on completing a month of leave before taking on any other project… and ended up going back to my last project in the Red sea. 

 

The flight tickets were received two days beforehand. I had just two hours in New Delhi Indira Gandhi airport to change my flight and a 12 hours interlude at Jeddha. I would have liked it the other way around.

Cab rates keep raising every time I travel ‘diesel price hike’ is the persistent retort. Travel allowances however stubbornly remain unmoved. The driver lost his way and was a bit late. There being no traffic jam, it won’t matter; but if we get in a jam, it could mean losing the flight. For ease of identification, I deliberately bought the purple color big sized ‘American tourister’ trolley bag, which soon was going get lost. The black laptop bag however have been my constant travel companion for the last three years.

At the market place, at nine thirty am just opened for business,Internet shops awaited bhoni (first) customer. Snail paced computer at the first cyber cafe won’t detect my pen drive. I rushed to the next Ganesh cyber café, at the first floor up stairs through a grounf floor Xerox shop. Just Re.1 for a computer printout was cheap; at the airport the airlines charge a hundred rupees for a ticket print. Thought of getting late kept pilfering my mind, for some strange reason I don’t put on a watch, some day I intent to give up the mobile too. I ran back to the car, parked under the shade by the driver, for his convenience.
 

 

Rest was a cozy drive, the driver initiated some conversation but I was more interested in a nap. Traffic was expected, as we were to traverse the ghats of the holy river Ganges at Haridwar, it being the first day of navratri (Hindu festival of nine days of fasting), but was pleased to find an uncongested road. Except a little halt at the rail crossing the travel went uninterrupted from Roorkee via the holy city of Haridwar to the Jolly Grant airport, Dehradun.

I gave the driver the fair of 1250 Rupees; he reminded me that I had paid him 500 bucks at the petrol pump. As I collected my ticket the flight security check announcement was aired. Although I had a connecting Air India flight from Delhi to Jeddha the attendant won’t issue the ticket till Jeddha and so I have to collect my baggage at Delhi and deposit it back to the same airline for the international flight. It raised my concern as I had just 2 hrs at Delhi to change to the flight. Nevertheless the flight being on schedule was some relief.

On asking, I had a window seat, owing to the seat  (mis)alignment it had no window. Receiving the checked baggage on arrival in the early lot was yet another relief. I walked out of the airport and took the  lift to the departure terminal.

Lucky there was no crowd at the immigration. I found an idle immigration counter and had some spare time for my favorite task at the airport - pick up a business today and a couple of friction books.

I had the least preferred middle seat in the large (10 seat in a row) aircraft.  Fortunately the aisle seat was vacant which I duly occupied. And had the vacant seat to keep my books, magazines and newspapers. However I didn’t read as the entertainment system had a wide collection of movies and serials, after a much needed nap I ended up watching some (bullshit) comedy. International fights to Saudi don’t serve drinks; still it was pleasant, to notice that he air hostess didn’t mind serving extra meal, although I had my fill in a single serving. I had a 5 and half hours of cozy flying time.

 

The agent was nowhere around and the couple of Saudi STC mobile sim declined service. India aircel sim with 170 INR balance displayed ‘low balance’. Sometimes when you are struck, nothing works. I wondered, absent instant communication, what life would had been, just a decade back.

Half an hour passed and suddenly the mobile buzzed, Thankfully the STC sim I just happen to insert in my Galaxy tab, had incoming still active. The flash back went that the secretary had called my wife mentioning the agent didn’t find me at the Jeddha airport and so she was trying my Saudi numbers and as a matter of good fortune, one worked.

 

Soon the secretary too called me up.  Half an hour later the agent also called stating that an agent will reach me in another half an hour. Joy the coxswain too arrived from Kotchi, in the Colombo flight. Now, two is a company.  We waited for an hour, then made a request call through a cleaning Indian staff phone to the secretary. The agent arrived at 10:30 pm, 4 and half hour after schedule.

 

Past immigration at the collection point, my baggage was absent. I finally got a copy of property irregularity report (PIR) in exchange of the checked in baggage slip. Next surprise was instead of hotel, we were being shuttled to the domestic airport. 12 hours hiatus and would be spending the night at the terminal. ‘Welcome to Saudi Arabia’.

 

Salespeople don’t understand English even at the international airport, however overcome the language handicap through sign language, adding to the grievance, at the local SAWA sim counter, no new sim numbers were available.  

 

As if it was not enough, the driver who left to get the car was again lost. Once more I had to borrow phone from a kind Pakistani passenger and called Mariafe intimating her of the lost baggage and the missing agent cum driver; who suddenly made appeared in the middle of our conversation. incidences and coincidences were events of the night. It was 1230 am when we left the international airport and shuttled to the domestic one. ‘khuda hafiz’ the agent left.

 

We took the seat near the cafeteria and slept, waking up intermittently. Finally at 4 am got fresh in the wash room and went for a cup of tea.

 

Black tea cost 6 riyals while milk tea cost 4. I placed the cup on the table and went to fetch the sugar and starrier. The table with one shorter leg skewed, pouring all the tea on my only trousers, table and the floor. I went for another cup, the counter guy knowing of the cup slipped offered for free. Small gesture well appreciated.

  

After the security check, it was cozier inside the airport with a better shopping facility. I ended up frenzy shopping, some needful items after losing my luggage – vest and underwear and intuitively buying an explore laptop bag and a wireless headphone. Shopping is not cheap at the airport still shopping beats stress, I realize!

For my third and the last flight I had the first seat in business class. After a sully night at the terminal, I leisurely enjoyed the space, coziness and breakfast. Early morning it felt cool at Tabuk. God gracious it’s not yet desert hot; was hotter back in India.

The driver was waiting. Initially he didn’t mind me calling office on his phone, the next time however he came up with excuse of 'low balance'. For the first time I had a driver who did not play the local music although he had some old fashioned audio tape cassettes, instead he sang to himself. People here love to sing songs or recite Quran. He paid for his tea and breakfast, quite unusual as habitually you pay for the driver meal and refreshments. I went for a nap on the way, driving across the paved road across the desert hill terrain.

Two hours drive across the hills and valleys we were at the Al-Fal hotel at Duba. Joy, who was on another flight had arrived ahead of me. The manager offered one two bed room to us. Customarily each person has his own hotel room. I don’t know yet, if it is the agent or my company, compromising the standard!

A double breakfast felt invigorating, omelets and egg bhurji (scrambled egg) with kafoosh (local bread), on the roadside table. Walked down the road looking for SAWA sim outlet, it being Friday, we were received by closed shops. Tired of the travel and the long walk around the town, I slumped in the hotel bed. Late lunch, large mutton biryani plate for 20 rihyals, at 4 at the malyalees run restaurant. Against hop, we walked up to the SAWA shop to find it closed once more. Local and molyalee shopkeepers opened for business at 440 pm after the namaz.

Sent a mail to office, agent and the airlines about the misplaced baggage. The day passed without any news of the baggage so evening at 8 walked in the nearby supermarket and bought toiletries and clothes.

The next day morning saw us walked back to the SAWA shop and finally we managed to obtain a new sim. For breakfast omelets, khapoos with black tea was served in the room.

 

                                                                                                  

   to be continued...

An orientation to the fascinating Multibeam systems for underwater mapping!

Other than communication, sound has brought upon far reaching consequences upon human endeavor for exploration. Multibeam has ever been a fascination among hydrographic surveyors and engineers. It was pioneered in 1970, but lately has evolved into mature commercially viable system.

Hereby is presented an orientation of incredible multibeam systems and the factors influencing its image compilation. Although the following discussion does not have the scope to provide a definitive response, it may shed light on some of the issues.

On the decibel scale, everything refers to power, which is amplitude squared. 0.0 dB corresponds to about the normal threshold of hearing and 130 dB to the point where sound becomes painful to humans.

Multibeam systems broadly can be categorised into two:

Interferometric (determine angle as a function of travel time) with swath width of 10-12 times of the depth are good for overall bathy and are less expensive (i.e. GeoAcoustics) while beam forming (measure travel time as a function of angle) use mill cross arrangement with swath width 3-4 times of depth is viable for detailed bathymetric and target identification (i.e. Reson, Simrad).

Bernard Mill, who first used this technique in 1954 referred as Mills Cross technique in a two-dimensional radio telescope.

Each arm of the cross was 1500 feet (450m) long, running N-S and E-W, and produced a fan beam in the sky. The voltages of the two arms were multiplied to form a pencil beam with high side lobes. The beam could be steered in the sky by adjusting the phasing of the elements in each arm.Received echo beam forming systems utilize two orthogonally mounted transducer array (projector and hydrophone). The transducer transmits a pulse that is flat (disk) shaped. The receiver receives a return signal that is also flat (cone) shaped and by placing the TX and RX arrays perpendicular to each other and using signal multiplexing a “beam” is formed.

 

In Interferometric system multiple horizontal acoustic elements are housed in a single unit for port and starboard to compare the phase of each incoming echo sample, thus allowing the angle to be calculated.

A limitation here is that at nadir the geometry of the returned echo makes it difficult to resolve phase shifts which may lead to ambiguous depth measurements… In practice however with the current state of art technology, this limitation stands more or less resolved.

Interferometry makes use of the principle of superposition to combine waves in a way that will cause the result of their combination to have some meaningful property that is diagnostic of the original state of the waves. When two waves with the same frequency combine, the resulting pattern is determined by the phase difference between the two waves.

 

Interferometric sonar , also referred to as Phase Differencing Bathymetric Sonar (PDBS) systems, use the measurement and comparision of phase at each of several horizontal line arrays (receive elements )to determine the angle from which the acoustic return originates (backscattered sound waves from the seabed. To conclude Multibeam systems don't actually use the interferometric method of superposition of signals.

 

In acoustics, beam steering is used to direct the audio from loudspeakers to a specific location in the listening area. This is done by changing the magnitude and phase of two or more loudspeakers installed in a column where the combined sound is added and cancelled at the required position. This type of loudspeaker arrangement is also known as a line array.

In beam steering echo sounders, the echo footprints get large as the angle of incidence increases; interferometric systems give high resolution images to the outer edges of the swath. However with advent of technology, Beam steering echo sounders come with the option of equiangular and equidistance transmissions so settlement upon a better system is disputed.

The data quality is determined by the reflected (actually refracted) received beam brightness (amplitude) and colinearity (alignment).

 CTD (Conductivity, Temperature and Depth) conclude the velocity of sound (speed of sound in water).

Temperature is the prominent factor affecting velocity. 165 meters depth change has the same effect as 1 degree centigrade temperature change. Thermoclines (sudden temperature changes) also occur near the surface.

Salinity increases little with depth.

Pressure increases rapidly but water being non compressible has little effect on velocity.

On Reson displays a sad face indicates local sound velocity less than reality and smiley face indicates local sound velocity more than reality. However such faces may also be due to indifferent spreading or absorption values in Reson Ocean Menu.

Absorption is due to the loss of acoustic energy to heat while propagation. Higher the freq. - higher the absorption.

Of the available range of 0 to 120 dB/km, in case the exact value is not known, a value of 60 -110 dB/km for salt water and 70 dB/km for fresh water is recommended for a high freq 455 KHz high resolution Reson multibeam. While for Simrad 80 dB/km is recommended. However operator prudence must be employed. Operator prudence is much however much required.

Spreading loss is because the total amount of energy remains the same in the wave spreads out of the source. As the wave spreads with time and distance, energy per unit length of the wave is diminished. Intensity falls off for square of the distance, 6dB for each doubling of distance.

In Reson system, out of the range of 0-60 it’s recommendable to begin with 30.

Bottom absorption varies with freq., bottom type and grazing angle. Losses increase with freq. and grazing angle.

For 24 KHz with 15 degree grazing angle the approx. absorption is:

Rock 20dB/m2
Sand 30dB/m2
Mud 40Db/m2

Beam width depends upon the length of array and freq. Elements of the array is spaced half wave length apart. More elements in array, narrower the beam along with higher the freq., narrower the beam.

Beam steered in a direction other than perpendicular to the direction of array by applying a variable delay to the signal from each hydrophone.

The data transmission is primarily through User Datagram Protocol. It employs minimum protocol mechanism with no handshaking.

UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact.

A port is a software structure that is identified by the port number, allowing for port numbers between 0 and 65535.

Port 0 is reserved, but is a permissible source port value if the sending process does not expect messages in response.

The Internet Assigned Numbers Authority has divided port numbers into three ranges. Port numbers 0 through 1023 are used for common, well-known services.

Port numbers 1024 through 49151 are the registered ports used for IANA-registered services.

Ports 49152 through 65535 are dynamic ports that are not officially designated for any specific service, and can be used for any purpose.

Source port number field identifies the sender's port when meaningful and should be assumed to be the port to reply to if needed. If not used, then it should be zero.

 

Destination port number field identifies the receiver's port and is required.

In Reson 8160, 8101 UDP Ports are 1028 (Multibeam data,) 1029 (Latency) and 1034 (snippets data). Reson 7101 use UDP Port 8000 and 7125 UDP Port 7000.

Simrad EM3002 SIS/HWS (Seafloor Information System/ Hydrographic Work Station) has two network cards to connect to PU (Processing Unit) and the online acquisition computer.

PU UDP communication in Simrad system Host UDP 1 to 3 (Port 16100 to 16102) is for communication between Processing Unit (PU) and SIS computer. For communication with the online acquisition computer Data distribution module is employed. Host UDP 4 (Source Port 16103, 16104) and (destination port 2012, 2040) on QINSy is used to transmit raw and Motion applied Multibeam data from SIS computer.

However other UDP Ports numbers also can be assigned.

Multibeam requires MRU string with high update rate (25-100 Hz), Gyro HDT string (1-10Hz), Navigation ($GGA, $GLL and $VTG) or RTK input, online SVP, over the side SVP profiler profile and Time synchronization (PPS).

Time associated with event goes serially to acquisition software, usually a $ZDA string. Systems with high depth i.e. Reson 8160 don’t need a PPS BNC input but only a $ZDA string.

For PPS sync, position to Simrad Processing unit (COM1) should contain ZDA string along with GGA. (GGA, ZDA, HDT, VTG etc are transmission protocols of NMEA (National Maritime electronic Association)

Datum, position and heading have no effect in raw Multibeam data. So datum selection is not necessary.

In case an INS system is not being used (i.e. POS MV or F180) aid motion sensor with GPS $VTG (speed), $GGA, $GLL and gyro $HDT strings, this helps a lot with the 'race tracking' effect (i.e. helps it settle quicker after turns).

For high data rate applications it is necessary use Ethernet.

If you connect MRU to Simrad Processing unit (PU) Pitch, Heave and Roll will be applied in SimradMBE.fbf file so use SimradMBERaw.fbf for post processing. If you are using SimradMBE.fbf file, disable motion correction during post processing.

There is much more to Multibeam encompassing its installation, calibration, maintenance and troubleshooting which call for more future discussions. Cheers!

 

Pos Marine Vessels – An efficient leap in integrating survey systems.

POS MV is a GPS Aided Inertial Navigation System. POS MV blends GPS data, together with angular rate and acceleration data from an IMU, and heading from GAMS to produce a robust and accurate position and orientation solution.

With single control unit for two DGPS antennas and one IMU, it makes the survey spread reasonably compact and easy to mobilise, it has five input /out put serial ports with NMEA Binary and other options. One USB connection, UDP Ethernet port 5602 with receiver slot no. on QINSy 102 and 103 and one BNC connector for PPS. It is designed to be a complete integrated solution for measurement of position (latitude, longitude and altitude), orientation (roll, pitch, and heading), heave, velocities and performance metrics.

 

To find out the Pos MV IP address, connect serial cable to Com 4 and check on HyperTerminal with 9600 bauds.

Inertial Measurement Unit (IMU) is a combination of orthogonal triads of accelerometers and gyroscopes (“gyros”). It being a strap down is easy to install.

 

IMU is also employed for Inertial Navigation, to compute a position from its measurement rather than using it just as a motion compensation unit. With a known Position is given to the IMU, it will be able to integrate acceleration and angular rate to determine its displacement and calculate a new position. Thus allows working in poor GPS environments.

 

 

 

For navigation POS MV has provision for two Auxiliary GPS inputs used to input a corrected position and two Base inputs used to input corrections.

 

POSMV combines the best of both - GPS and Inertial systems. The IMU and GPS work together so that even if GPS drops out the system can still provide a robust solution.

 

POS MV 320 uses Inertially aided RTK technology. The system provides position, heading, altitude and heave data using inertial / GPS technology. Its high update rate is specifically useful for Multibeam systems enabling adherence to IHO standards on sonar width of greater than ± 75 degrees under all dynamic conditions.

 

GAMS (Gps Azimuth Measurement System) calibration relies on the vessel making a series of dynamic maneuvers, making the IMU heading data as accurate as possible. The GAMS calibration is easy with only the offsets and liver arms to be correctly measured and entered in the software followed by rotational movements in the figure of eight preceded by a straight line.Once this has been achieved the system self calibrates and calculate a separation and XYZ offset. Multiple calibrations are to be conducted and results post processed to check for uniformity.

 

GAMS computes a carrier differential GPS position solution of an Antenna B with respect to an Antenna A and thereby computes the heading of the A B antenna vector baseline vector. It uses roll, pitch and heading from the S/D navigator to aid in the resolving of phase ambiguities and to check the validity of the GAMS solution. GAMS being self-calibrating; the user can place the antennas anywhere on the vessel. GAMS will measure antenna baseline with respect to IMU axes with no need to survey in components. GAMS Provides heading aiding to the IMU data.

 

IMU will drift over time when sailing in a straight line, IE running a survey line…

 

GAMS Aiding help the system produce a reliable heading solution when long straight lines are run the system looks at differences in the carrier phase signal to determine heading from the dual antenna system. It only need to know the relationship between the two antennas to do this well.

 

One of the few limitations is that at certain locations good satellite coverage is unavailable so the position accuracy may be beyond acceptable limit for some time.

 

Another limitation is that the differential is not Real time unless you have a Reference station setup for RTCM input. It takes up to three days to visualise the final processed data in the processing software POS Pac.  

 

POS Pac with reference to the recorded raw position observation log file finds the Base Stations, download, and import base station data which is publicly available on the internet. It also downloads precise and broadcast ephemeris files.

 

POS Pac scans imported base station files to ensure quality. Quality Check requires 18 hrs of continuous data and precise ephemeris files from three days (previous, present, and next).

It performs a network adjustment on the station coordinates, with one station selected as the control station. SmartBase QC will recommend action, but the user should still apply some “local knowledge”

 

GNSS and Inertial observables are simultaneously processed to create the Smoothed Best Estimate of Trajectory (SBET) solution. The Raw files  (.001) finally get to be processed (sbet_----.out).

 

POSPac MMS provides a PPP (Precise Point Positioning) solution. PPP is a robust and easy to use solution providing decimetric levels of accuracy no matter how far the shore or GNSS base station infrastructure.

 

IN-Fusion PPP provides increased solution robustness with radically simplified workflow

It also provides the capability to maintain PPP convergence should the number of satellites tracked drop temporarily.

 

POSPac MMS can estimate errors in lever arms applied in real time, this is often useful in validating both the surveyed values, and the interpretation of those values.

Finally observables from POS MV, public and dedicated GNSS base stations, as well as precise clock and ephemeris data are all used to produce the optimal result. The time budget is three days for the same.

In all it is a robust, easy to mobilize, calibrate and operate.

Poartable Desiel Generator - Trouble shooting tips!

Power generating equipment is a vital concern for boat surveys…. Some tips on portable marine generators…

Fiscar Panda 5000i silent marine Generator. With no noise it is a great system. Hope the same had been true with the Out board motors, Boat surveys would be a peaceful job. However the generator being unused for 8 weeks… won’t start!

Point to note…

Diesel engines should be run at least 60% to 75% of their maximum rated load. Short periods of low load running are permissible providing the set is brought up to full load, or close to full load on a regular basis. 

It's not really good for it to be run without load; it's like accelerating your car in neutral.

 

Diesel engines can suffer damage as a result of internal glazing and carbon buildup.

Internal glazing ( bore glazing or piling) and carbon buildup is due to prolonged periods of running at low speeds or low loads or when an engine is left idling as a 'standby' generating unit, ready to run up when needed. However eight weeks of idling is not a long time, for a new generator, to develop fault.

 

Trouble ( the narration…)

On start, the actuator moves to its position to let the fuel supply flow, after few seconds of preheating the pulley rotates, followed by some cranking noise, blows out grey (sometimes black) sooty exhaust and after a couple of jerks it stops. The starter is turning the motor, but fails to start.

Troubleshooting steps…

Step 1: Check the actuator moves to its position to let the fuel supply flow. Check the fuel actuator solenoid. If it gets built up with rust it may not want to release when the voltage is cut to it. This should have a rubber boot accompanied with spring center shaft that attaches to a governor control/fuel rail. If no actuation, check the connector for voltage, (directly off the harness).

Step 2: Check the battery … diesel engines require high power to start. A 12V starter battery is expected to dispense at least 12.6 V to kick it to start… While starting check the Voltage, it may drop up to 11V, if it goes lesser… recharge or replace the battery.

Step 3: Make sure that your fuel tank is not dirty with trash and if not....second go to the fuel pump the way to know is that when you turn it to run (not start) and vibrates.

Step 4: fuel filter and its line. Filter must be in good neat if those give dirty looks, remember that of the two filters one is the water separator. 

Step 5: Take out the nut from the fuel intake solenoid and bleed the air. You will have to shut the engine off with the throttle lever or remove the +ve connection on the starter solenoid, The ECU (Electronic Control Unit) will shut off the pump after some time… repeat the procedure a few times till air is fully bled out; or best don’t start the generator, start the fuel pump by a direct battery +ve connection to it.

Step 6: Next take out the fuel cut-off solenoid and remove the plunger and spring and then re-install the solenoid. Then bleed all the air out and start the engine. If that works check for loose connections and low voltage to the fuel cut-off solenoid. You may have flow but do you have pressure, is your fuel pump blocked slightly (this may have to be timed if you have more than one cylinder).

Step 7: Loosen injector line from the combustion chamber… while cranking see if fuel coming from injectors. At the injector pipe where it connects to the injector the fuel should shoot out with force. Maybe you have a clogged injector, this would cause a sputtering or spitting sound as it misfires accompanied with black smoke (unburned diesel). If you have good flow all the way to the injector, well.

  

Step 8: Glow plugs are there to heat the air or the block in some cases before compression of said air to raise the temp. before the diesel is injected. Diesel fuel doesn't require heating before use unless it’s severely cold and the fuel has solidified (and that doesn't happen much especially with the additives they put in it now).

To initiate the combustion (if it’s not happening by the standard system) ...squirt a small amount of starting fluid into the air inlet (take the air filter off first). while cranking these diesels for extended periods, trying to start them, don't use starting fluid, use silicone spray lube, or wd 40 to give the upper end some lubrication, it also helps spin faster.

Step 9: Again on the checklist is electricity, but it won't govern itself. Often a generator has a governor control unit which may be electrical or mechanical.

If electrical check your wiring diagram first to ensure it’s connected properly and your connections are good you know corrosion or looseness. If yet not fixed, just save time and replace that component.

 If Mechanical, they usually run on oil pressure. If the oil is contaminated it may have clogged up the journals on this component. Removal is easy and an overnight stay in parts washing fluid should be enough. Installation is also easy don't worry it doesn't have to be timed.

The oil is getting blackish means fuel is mixing in the engine oil through the combustion chamber, in case the oil is getting whitish, it’s a water mixing in…

Under-loaded running inevitably causes white smoke from unburnt fuel and over time will be joined by blue smoke of burnt lubricating oil leaking past the damaged piston rings, and also black smoke caused by damaged injectors.

 Always check:

The water inlet liver has to be turned on before start & off after switch off. The water inlet is connected through a water filter and it has an adjacent water outlet.

Placing a primer in the fuel line for priming oil… is a good idea.

Usually portable generator is connected to Inverter for AC power; In case, you are getting AC… it may be the inverter. The inverter also supplies power input to the battery charger.

Some more Information:

 

Electronic Diesel Control is a diesel engine fuel injection control system for the precise metering and delivery of fuel into the combustion chamber of modern diesel engines.


An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. It can be electrical, mechanical or software based. Actuators or solenoids convert the control unit's electrical output signal into mechanical control movement.

 

These topics are broad enough to merit new discussion…. so the next time. Hope you got some tips …& it was interesting too. Do comment!