Introduction: Laser Quadrat for Coral Reef Mapping

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What is a "laser quadrat"?

It is an upgrade of a conventional quadrat.
The goal is to make coral mapping:

  • more accurate
  • affordable
  • faster
  • safer

The Issue
We are interested in mapping coral reefs. We are specifically concerned with any changes to the coral formation (size & shape) and health (color). Most structures that we call "coral" are, in fact, made up of hundreds of thousands of tiny coral creatures called polyps that live on the seafloor. They usually live in shallow water, where conditions are right for most corals to grow.

Coral is very important because many marine organisms live and breed around corals, and if corals dies, the fish that lives around in them are left homeless and the fish may die. Then, their predators die, and so on, we call this a "Trophic Cascade". This is why corals matter.

Corals are extremely sensitive; to coral reefs, a little goes a long way. Even a very tiny change in temperature is enough to stress out the corals and cause the coral to bleach. Corals can recover from bleaching if temperatures go back to normal, but prolonged bleaching might eventually kill the corals. Global warming and El-Nino in particular, anchor-dragging (must watch video), cyanide and dynamite fishing, other forms of water pollution, poaching, are causing unprecedented stress on coral, but it takes hundreds of years for corals to fully regenerate.

Current monitoring only allow for small areas to be studied at the time. We hope to upgrade coral reef mapping with laser technology.

[Text by Thomas]

We have entered 3 competitions, please vote for us, thank you!


Step 1: The Issues and the State of the Art

How do we measure coral reefs right now?

Coral reef scientists currently use a cumbersome, intrusive quadrat. To measure coral, they need to and drop the quadrat on the coral, potentially damaging coral while trying to study and protect it. Coral take years to regenerate, yet they can be damaged in seconds. What is the use of measuring corals’ health when you are damaging it yourself?

A laser quadrat is meant to be non-invasive, lighter, and harmless to corals. We do not expect the laser to be more intrusive than a camera flash. Damage to fish eyes is unlikely as the laser may come into contact with their retina for a negligible amount of time.

This is still at the prototypical stage, we intend to replace red lasers which don’t shine very well in blue/green water with green lasers.

[Text by Thomas]

Step 2: Draw the Ideas on Paper

An early step in the process is to "let the kids imagination run wild". And individual drawing allows each student to express their ideas to the group and learn from each others. Many interesting ideas came out and we tried to eventually combine all these ideas into a functional design.

Step 3: Take a Laser Equipped Device Apart

We started by taking a construction site laser. We choose to hack this laser because we wanted

  • to make sure the laser is not too powerful and harmful to human / animal eyes
  • to understand how a laser is powered
  • to understand how lasers can be aligned
  • because hacking electronic is real fun

We found out later that "cross hair laser" are a more accurate and efficient way of producing a "square"

Step 4: Cut Viewfinder and the Waterproof Joint

For the viewfinder, we cut a plastic sheet 2 cm wider and longer than the aquarium lid. It would have been better to laser cut it. The waterproof joints were the same size of the viewfinder, with a hole 2cm narrower and shorter than the perimeter of the lid, to allow a clear view of the screen of the device that is recording. Cut out two of them, then attach them to either side of the viewfinder.

[Text by Brandon]

Step 5: Build the Handles

When we found the right sized board then we measured 25 inch

We cut the board into 2 equal sized pieces 12 and a half inches each then we drew out a line of where the handles are supposed to be. We sanded the inside of the handles and the sides of the board with sand paper and made sure that it was comfortable. We carved out the handles with the milling machine.

[Text by Eitan, Kai, Ntando]

Step 6: Cut the Rods

  1. After getting all the materials ready, measure the height of your apparatus.
  2. Keep in mind that the rods should be cut with enough overhang for a washer and a bolt to be applied (22cm)
  3. Cut four metal rods to the desired length using a drill press.
  4. Once cut, round of the tips of any excess metal to avoid causing injury.
  5. Place rods into pre-drilled holes in top and base of apparatus.
  6. Apply a washer and bolt to each end of the four rods to apply pressure and make water tight

[Text by Brendan]

Step 7: Laser Jig

Cut the acrylic
Assembling the laser was complicated, considering we had to hack the laser and place the four lasers into an 8 cm by 8 cm square for the quadrat size. We used red lasers (but green or blue would work better in the water because red light doesn’t penetrate deeper water well). You have to align two lasers vertically and two horizontally so that the square shape would be consistent. We put our lasers diagonally, but you can place them differently as long as they still align to make the desired shape. The lasers will help measure the objects and with mapping.

Step 1: Assemble materials

  • 4 working lasers (that project lines, not points)
  • Acrylic rectangle (or chosen shape) of transparent material that fits the small aquarium
  • Blu-tac for positioning and Hot glue to stick the lasers with 8 cm by 8 cm
  • Square piece of paper 8 cm by 8 cm for close and distant calibration

Step 2: Aligning the lasers

  • Position the lasers on the piece of transparent material so that the projected lines point down
  • Try to align the lasers into a square, helped by the 8 cm by 8 cm square piece of paper
  • Make sure measurements are precise

Step 3: Test lasers

  • Does the shape stay the same size, even from a distance?
  • Does it fit the template?
  • Are all the lasers are working properly

Step 4: Attach lasers

  • Attach lasers to accurate point to create the desired shape
  • Make sure to test if the lasers are sturdy
  • Make sure the adhesive doesn’t interact with the light

Step 5: Final testing

  • Make sure the lasers don’t move
  • Make sure everything is stable
  • Make sure the battery can be switched on and off
  • Make sure the materials can fit into the rest of the machine. If not, reposition.
  • And you’re done!

[Text by Varia, Kristen, Maya]

Step 8: Assemble

Put all the parts together.

  1. Take the lower wooden frame and position the metal rods with a nut and a washer at the bottom
  2. position the aquarium so it fits on the window
  3. switch on the laser jig
  4. Insert phone and start recording video sequence
  5. Insert the laser jig inside the aquarium
  6. Insert the acrylic viewfinder, make sure the joint overlaps with the edge of the aquarium
  7. Take the upper wooden frame and slide the metal rods through the holes
  8. Insert the 4 washers and tighten the 4 bolts
  9. You are ready to go film underwater with your laser quadrat!

3D file (sketchup) attached with all the parts specs

Step 9: Test at MakerBay

After assembling the machine, we first tested it at Makerbay. We made sure that the lasers were forming a perfect 8x8 cm square, and we made sure that the square that was formed stayed exactly the same no matter how far the device was from the target. The test at Makerbay went smoothly, and thus we proceeded to test at the Swire lab. We did not know if the device was watertight lab.

[Text by Brandon]

Step 10: Test at Swire Institute of Marine Science (SWIMS)

When we came to SWIMS we introduced the issue of solid quadrants which are used to measure coral at the moment. We told them about our concern that these solid metal quadrants might damage the coral when they are used for measuring. After explaining the issue we introduced the laser quadrat which -we hope- will not damage the coral but will still perform the same task as the current one. Before assembling the little machine we showed the parts to build this invention.

After we finished explaining our project the scientists from Swire had some presentations explaining what they do. We got told about Infared photography and how this could be used to identify different types of species on sea shores. Biological Engineering was our next topic that was brought up, he was talking about how Hong Kong was building breakwaters that protects the land from dangerous waves.

At Swire we had the extraordinary opportunity to test our invention in their water tanks with coral. After re-assembling the laser quadrant we put it in the tanks, with the recording we could later put the video into a coral map.

[Text by Ntando, Gustaf]


[Awaiting Scientists feedback by Kirsten]

Step 11: Test at Sai Kung Country Park

After we kayaked for about 15 minutes, we tied our kayaks to the buoys. That’s where we were going to map the corals using the laser quadrat. We swam around for about 10 minutes looking for a place to map then we decided. We first assembled it and then picked 3 volunteers (Kai, Eitan, Brandon) that were going to map the corals using the laser quadrat with Cesar. The laser worked pretty well and we managed to get enough footage so we could make a map later.

If you want to go to map in " target="_blank"> Hoi Ha Wan please

ask permission to access the area to

  • do not touch or step on coral
  • do not anchor
  • do not pollute the water with your sunscreen, insect repellant, sodas, urine etc
  • do not litter
  • do not disturb marine life

Location map: 22.463522, 114.330659

In the pictures you will see the details of the local companies that rent kayaks, life jackets, snorkel gear and more.

[Text by Eitan, Kai]

Step 12: Create a Map

There are many ways to assemble a map. We used photoshop but there are tons of other tools there.
We love Mapknitter, we're looking for something similar for coral reefs.
Map making will be another instructables.

We hope you enjoyed these instructions and we would love to have your feedbacks and suggestions to make our laser quadrat even better.

The Laser Quadrat is Licensed under the CERN Open Hardware License. For the environment!

2013-04-10 open hardware logo


Great thanks to

  • Director Gray A Williams, SWIMS
  • Assistant Professor Dr David M Baker, SWIMS
  • Mr. Brendan Fielding, THS
  • Mr. Ahmet Arduc, THS
  • Carmen Kwok


  • "Low Rider"- War
  • “Aquarium” - Camille Saint Saens
  • Cameo : Shawn Frayne
  • Deep voiceover : Alex Hornstein


Animals in the Wild Challenge

Runner Up in the
Animals in the Wild Challenge

Outside Contest 2016

Participated in the
Outside Contest 2016

DIY Summer Camp Challenge

Participated in the
DIY Summer Camp Challenge