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ECHOLOGGER mini Sonar


(Todd Sparkes) #1

If anybody is interested in a good performance sonar head have a look at echologger.com


(undersearobotics.com) #2

We gave Echologger a look. Prices seemed pretty high and we weren’t able to find anyone with any hands on experience with them. Nice to see another competitor in the market though. Do you have one, and if so, could you share your experiences with it?


(Todd Sparkes) #3

Hey Paul. No I don’t have one personally. $5600 for the 1000 meter version is cheaper than a lot of brands such as Tritech.


(undersearobotics.com) #4

$5,600 USD right (not CAD)? About the same as the Imagenex 852 price wise. Looks interesting but like everyone else I’d really like to see a scanning sonar for half (or less) that price.


(Todd Sparkes) #5

I hear ya Paul.Hopefully a product with a decent scan image.


(undersearobotics.com) #6

I had hoped to adapt the Garmin Panoptix for use on ROV but kept running into “road blocks” and gave up. I later got a call from an engineer at Garmin who wanted to revise the firmware so the transducer could work with a laptop. Although that sounded like good news at first I haven’t heard from them since.


(Todd Sparkes) #7

ThinkSensor seems to be trying to put out a unit around the $2000 range but I am not sure what they will offer or what success they will have building a quality unit.


(Pavel) #8

Hi Paul

We are currently working on getting out our sonar block asap. The initial 300 kHz version should have a range of around 150 meters and be priced close to $1000USD. We are also planning a 450 kHz version and make a version go up to 1 MHz. Our main experience is in 3D interferometric sonars on a rotator designed for industrial marine engineering applications. The sonar block will be our first entry into this low cost market. The main challenges in making a high quality affordable sector scan sonar are the transducers and the rotator. In discussions with Rusty, the BlueROV2 should be capable of executing a very slow turn in one location, allowing us to do a sector scan by rotating the ROV. If this works, it would be a very affordable way to do a sector scan The sonar block would be mainly mounted in a side scan configuration on the ROV. We plan on looking at a rotator mount for the sonar block after we have released the initial product.

What frequency are you looking at for your application?
What beam width would work for your application? Currently our 300 kHz will have an expected beam 2.5 deg x 120 deg

Thanks,
Pavel Haintz
Think Sensor Research Inc.


(undersearobotics.com) #9

Although this might be possible (in ideal environmental conditions) it certainly wouldn’t be practical on an ROV. Keep in mind, a sector scanning sonar on a ROV is used primarily for navigation in poor visibility. It’s hard enough to navigate a straight line using a conventional sonar much less having to stop and alter course to refresh the sonar display. Plus it completely defeats one of the BlueROV2’s biggest benefits over other, mini-ROV’s: that it is much more stable (in all directions) than other mini-ROV’s.

From my perspective, I’d much rather see something like the Garmin Panoptix adapted for use on an ROV. It’s a much more sophisticated technology yet still less than $2,000USD.


(Todd Sparkes) #10

I agree with Paul. If you are lost especially in bad visibility and if there are hazards or tangle points in the area stopping the ROV to rotate for a scan could be very bad. Transiting in bad vis requires real time updates to ensure you are heading in the right direction and also ensures obstacle avoidance.Also stopping to rotate for a scan in any type of current will most likely cause lose of position. A scanning unit is a necessity for a sonar unit.


(Pavel) #11

Hi Todd, Hi Paul

Thank you for helping us understand your application and requirements.

For the sector scan what range are you looking for?
Is it important to scan 360 deg, or can you just scan 120 deg in front of the ROV?

For shorter range, higher frequencies can be used and also the scan rate can be increased for mechanical sector scans, the main limit in sector scan rotation speed is the time of flight of the acoustic signal through the water, around 1484 m/s.

I took a closer look at the Garmin Panoptix, it is a multibeam. It looks like it is technology that Garmin bought from another company Interphase. The specifications sheet does not give the number of beams or the beam resolution, the display looks very blocky. The Ps60 down transducer is priced at $4k USD and the forward looking transducer at $1.5k USD. It looks like they use 8 receive channels at a frequency of 417 kHz, if they are using standard ceramic element spacing for multibeam, this would result in a beam width of 12.5 deg, this would explain the blocky display.

The main challenge for multibeam sonars is that to get a display with good resolution (i.e. high number of beams) requires a high number of receive elements (Channels). The Delta-T is 32 channels if I remember correctly. The R2 Sonic and Resons are 128 or 256 channels. The cost of production tends to go up exponentially with the number of channels.

We are looking into an under $10k USD multibeam.
What range are you looking for?
How important is the resolution of the display?
Are you looking mainly to avoid obstacles or being able to identify objects and terrain in front of the ROV?

Thanks,
Pavel


(Todd Sparkes) #12

Pavel,
In my opinion sector range of approx 120 degrees is sufficient. 360 degree is rarely used due to either the mounting location on the ROV blocks signals and usually you already know what is behind you.
Again in my opinion the 10 to 30 meter range is the most important, under 10 meters you can probably see and over 30 meters not required, the sonar will update as you head in the proper direction.
Resolution isn’t a big issue considering the sonar is meant to be used for obstacle avoidance and/or object location.
Detail on images comes with more expensive systems. I believe the goal for most people with a Blue ROV is just identify and avoidance.
Humminbird has an impressive looking system with Mega Imaging.
Some guys here will probably say 100 meter range is required. As a professional ROV operator even with very expensive systems this range is never used unless you are looking for massive objects. Also if working in shallow water you get mostly garbage feedback from the surface of the water.
For me if I am asked to do a survey it will be visual. The sonar is only used to identify obstacles as I go down a cable or pipeline.

Regards
Todd


(undersearobotics.com) #13

Yes, Garmin did buy the technology from Interphase but I think you’re mistaken on the pricing. The transducer that comes closest to our needs is the PS-31 and when paired with a topside unit like the GPSMap 741 brings the total system cost to just under $2300USD. A bargain compared to what we normally might expect to pay for an ROV sonar.

The resolution of the image can be changed in the settings, but higher resolution means slower scanning / refresh speeds. I had a unit last year and posted my experience in our company’s blog: http://marinesimulation.com/blog/

If Garmin were to offer a version that could be controlled / displayed on a computer it would be worth serious consideration. Especially if it were to be used with the Blue Robotics Fathom-X boards.


(Pavel) #14

It looks like the PS-31 is the forward looking transducer and the PS60 ($4k USD) is the down looking transducer https://buy.garmin.com/en-US/US/p/503834#

The PS60 may have more receive elements than the PS-31, the Interphase sonar originally had an option for 3 x 8 RX channels.

The display looks very low resolution, probably do to using a standard multibeam algorithm on 8 RX channels.

I would be very surprised if Garmin released their communications protocol. Their commercial products tend to be closed systems. Their target market is pleasure crafts and fishing sonars which is probably much bigger than the ROV market, at least for now.

All of our sonars will have the communications protocol released so they can be used with any software.

On the ROV sector scan it sounds like something like a 675 kHz high speed scanning head would be more useful than a 300 kHz head.

Lets assume that for the ROV you would like to scan a 120 deg sector, with a range of 30 meters in front of the ROV. Taking speed of sound at 1500 m/s, this would give a maximum of 1500/(230 meters) = 25 pings /second.
Assuming a step size of 2 deg, it would take you 120/(2
25)=2.4 seconds for a sweep through 120 deg.

Would this update rate be fast enough?

You could decrease the step size for more resolution and/or decrease the ping rate for greater range. At 675 kHz maximum range should be around 50 meters. The beam width would be 1.1 deg for our 675 kHz transducer, giving the option for very high resolution sector scans.


(undersearobotics.com) #15

No, the PS30 (same price as the PS31) is the down scanning equivalent: https://buy.garmin.com/en-US/US/p/149188 The PS60 is intended to be permanently mounted to the boat hull. My guess as to why it is more expensive is that it is probably much more rugged as it is designed to be permanently installed and subject to grounding, marine growth, etc. The PS31 / PS30 include stainless steel brackets that can either be mounted to the boat’s transom or to a trolling motor.

I’m told the only difference between the PS31 and PS30 is in firmware. Besides the multibeam transducer, the PS31 / PS30 also have a built in AHRS so it can automatically sense pitch / roll and compensate for it in the display. During my testing, the AHRS did a nice job of stabilizing the image.

I thought the resolution and refresh rate were “good enough” for our purposes. The only things that were disappointing were the size and weight of the transducer and that the only way to display the sonar image was through a Garmin topside controller/display. At one point it seemed that Garmin might consider changing this, but I’ve not heard anything further in over a year.

One thing I didn’t have a chance to test (and I think would have been worthwhile) is to see if the ethernet from the Panoptix transducer was compatible with the BlueROV2 Fathom-X boards.


(undersearobotics.com) #16

Leave it to Humminbird to come up with even better side scan imaging! By adding a higher frequency they’ve improved the resolution of the side scan image exponentially.

But side scanning sonar on a ROV isn’t intended for navigation, its data is historical (ie. tells you what the bottom behind you was like). Instead, it could be very useful for creating high resolution sonar mosaics. The issue you’ll run into is that side scan requires real time location (usually provided by a GPS). In theory at least, you might be able to get that from something like the new “underwater GPS” system. I’m sure @kevink might have an idea or two on how to accomplish this…


(Todd Sparkes) #17

Pavel, Yes 2.5 secs is fast enough for a scan.


(Kevin) #18

I concur with @paul-unterweiser that side scan on an ROV isn’t very useful. You need consistent speed and direction to get good imaging results. It’s better on a towfish, but best on a UUV because you can also get consistent altitude.

I have a design in my head for a thrust-based UUV (instead of one with fins) but I will need a detached receiver from the Water Linked system. For the side scan system I was thinking of using a DeepVision HM680D (http://deepvision.se/products/side-scan-sonars/) all it would need is GPS injects from the Pixhawk or companion computer. And I’m not great at programming, so Jacob would need to come up with a way to have a NMEA GPS output somewhere that we could plug into.

It’s doable in the future, but not right now. Once we have that receiver, we should be able to program missions on the surface via WiFi, and send it down. I don’t think we’ll need acoustic telemetry starting out. Most micro-UUVs don’t have that anyway. So if you can live with the “hope” that your vehicle is doing its job and not entangled, we should be good :slight_smile:


(Pavel) #19

What would be the maximum size and weight of a sonar for the BlueROV2?


(Todd Sparkes) #20

Obviously smaller is better but weight isn’t really a factor, Ballast can be adjusted to compensate for the weight of the unit.
Below is the specs from a model currently available on the market.

Pulse CHIRP & CW
Driving Freq. 900 kHz
Beam Angles H0.8°, V30.0°
Max. Range 60m
Range Resolution 15 mm @50kHz , 7.5 mm @100kHz sampling
Rotational Contact Noncontact Transformer
Angle Resolution 0.1125°, 0.225°, 0.45°, 0.9°, 1.8°
Max. Scanning Speed 4sec @ 5 m, 0.9°
Transmitting Pulse Length 512 us (CHIRP), 10 - 100us (CW)
TVG 60 dB
Gain Control -30 dB ~ + 30 dB
Interface MRS RS232 / RS485 up to 3Mbaud
Motion Compensation Enabled using Compass & Gyro.
Power Supply 12 - 72 VDC, 6W Max
Data Transmission 2 Mbaud@300m, 115200 baud @1 km
Connector SUBCONN MCBH4M (MCBH8M)
Depth Rate 1000 m
Material Al (Hard Anodised)
Dimensions Dia.140 mm, Height 120 mm
Weight 2.6 kg(air) / 0.9 kg(water)