JolyDroneSP
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Raspberry Pi 3D mapping with radar

Thu Jun 11, 2015 4:53 am

Hi,

I just started playing around with a Raspberry Pi not too long ago and me and a friend wish to use it to 3D map an area, using a drone as a platform. After some research, I thought radar would work. However, I am not too certain and instead, have a few questions i want opinions on:

1.Is 3D mapping with radar on a raspberry pi feasible?

2.What antenna should I use? (Assuming, (1) is all green, I was thinking of using this one: http://www.adafruit.com/product/1030)

3. How many antennas should I use?

4. How do I fit multiple antennas on a Raspberry Pi? (Assuming I use the one I thought of using in (2) with the USB connector)

5. Any hardware suggestions? (e.g. I am pretty sure I need a wireless module for the Raspberry Pi as well, yes? Anything else?)

Thanks.

hamilc
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Re: Raspberry Pi 3D mapping with radar

Thu Jun 11, 2015 8:44 pm

First, what do you mean by 3D mapping using radar? Are you wanting to get a topographical map of the surface,i.e. determine the height of the drone above the ground as it flies along a track?

In any event, radar signal processing is not easy. You wouldn't use a wi-fi antenna and wi-fi for radar. Radar systems use a very directive antenna and/or very high frequency to get good beam resolution.

JolyDroneSP
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Re: Raspberry Pi 3D mapping with radar

Thu Jun 11, 2015 10:06 pm

hamilc wrote:First, what do you mean by 3D mapping using radar? Are you wanting to get a topographical map of the surface,i.e. determine the height of the drone above the ground as it flies along a track?

In any event, radar signal processing is not easy. You wouldn't use a wi-fi antenna and wi-fi for radar. Radar systems use a very directive antenna and/or very high frequency to get good beam resolution.
By "3D mapping" I was thinking of something like this: https://www.youtube.com/watch?v=KdOyviOuoUw.
(except with Raspberry Pi and radar signals)

The graphical image would be produced on an android tablet.

As for the type of antenna, I can't seem to a high frequency/directive antenna with a small enough form factor to fit the bottom of a drone. (Assuming the drone is about 400mm in diameter and can only take 500g of weight max)

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aTao
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 12:50 am

You would most likely buy a radar module with transmitter, receiver and wave guide antenna built in.

You might find that there is a laser range finder that will suit better.
>)))'><'(((<

JolyDroneSP
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 6:35 am

aTao wrote:You would most likely buy a radar module with transmitter, receiver and wave guide antenna built in.

You might find that there is a laser range finder that will suit better.
For the radar module, I found something like this: http://www.rfbeam.ch/products/k-mc1-transceiver/
However, I have no idea how it looks like physically and cannot find a picture of one either...

Hmm... I see what you mean about the laser range finder.
Would it be necessary to rotate it with motors should I want to detect 360 degrees surroundings?
Or would it be better to arrange an array of laser range finders?
If I use motors, I think it'll introduce new issues, seeing as to the sensor being mounted on a drone. (Afraid that the vibrations may cause inaccurate readings)

toxibunny
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 8:52 am

They can do 3d mapping with just camera photographs nowadays. I don't know if there are any libraries available though.. I bet the maths is terrifying.
note: I may or may not know what I'm talking about...

gordon77
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 9:00 am

JolyDroneSP wrote:
aTao wrote:You would most likely buy a radar module with transmitter, receiver and wave guide antenna built in.

You might find that there is a laser range finder that will suit better.
For the radar module, I found something like this: http://www.rfbeam.ch/products/k-mc1-transceiver/
However, I have no idea how it looks like physically and cannot find a picture of one either...

Hmm... I see what you mean about the laser range finder.
Would it be necessary to rotate it with motors should I want to detect 360 degrees surroundings?
Or would it be better to arrange an array of laser range finders?
If I use motors, I think it'll introduce new issues, seeing as to the sensor being mounted on a drone. (Afraid that the vibrations may cause inaccurate readings)
It's shown on the link you posted, that square thing with the dots on it. If you download the datasheet it appears to have a 9 way connector on the back.

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topguy
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 9:01 am

> Would it be necessary to rotate it with motors should I want to detect 360 degrees surroundings?

That is the same for Sonar, Radar or Laser, they all just detect distance in a narrow beam, you will have to move the beam to sample the sectors/areas you are interested in.

I'm curious about which scale you are planning to do 3D maping on, room ? field ? valley ?

Measuring using radar I believe is only good for objects with high density, sound and light will bounce off most walls but radio waves will go straight through plaster and wood.

JolyDroneSP
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 6:03 pm

topguy wrote:> Would it be necessary to rotate it with motors should I want to detect 360 degrees surroundings?

That is the same for Sonar, Radar or Laser, they all just detect distance in a narrow beam, you will have to move the beam to sample the sectors/areas you are interested in.

I'm curious about which scale you are planning to do 3D maping on, room ? field ? valley ?

Measuring using radar I believe is only good for objects with high density, sound and light will bounce off most walls but radio waves will go straight through plaster and wood.
Ahh... I see... I forgot to consider the structure types we would be sensing...

In general, probably sensing anything from concrete to plastic, plaster, wood and even metal.
As for the environment, we would be mapping places along the lines of a corridor or room to a hall (at max)? Indoor usage essentially.

So I believe I would be using something like this: http://www.lightware.co.za/shop/en/lase ... rf-01.html
which is a laser rangefinder. (As aTao recommended)

However...
I can't seem to find anyone who has used it with a raspberry pi (without an additional Arduino circuit)....
Seeing as to how narrow the beam is for laser rangefinders, I am also worried about the level of intensity the servo motors have to move at and whether that would affect readings.

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jbeale
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Re: Raspberry Pi 3D mapping with radar

Fri Jun 12, 2015 7:12 pm

I am using a laser rangefinder with Raspberry Pi (LIDAR-Lite) and it works OK for typical indoor distances (< 10 m). Well, I am going through a Teensy 3.1 (like Arduino) first to convert to serial output, because I don't trust the R-Pi I2C link to be 100% reliable (eg. search for "linux hard real time")

The beam width is small, less than 1 degree. The peak sample rate is approximately 100 Hz but it is not constant (seems to depend on signal strength). It *might* be possible to expand the beam somewhat with an external single-axis diffuser but I expect that will cut down range, if it works at all, and it will likely report range to the strongest signal and not necessarily the nearest target. Might be interesting to try anyway, the Lidar-Lite is under $100. https://www.sparkfun.com/products/13167

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aTao
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Re: Raspberry Pi 3D mapping with radar

Tue Jun 23, 2015 7:12 am

If you want to scan a laser beam fast then use mirrors on motors, just like a laser printer/fax/copier. The motor/mirror can be minuscule, same size as the zoom or auto focus motor in a digital camera.
>)))'><'(((<

andrewjawitz
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Re: Raspberry Pi 3D mapping with radar

Wed Jul 22, 2015 5:49 pm

Hello,
I am looking to use the Lidar-Lite for 3D Mapping as well. Specifically, I am looking to incorporate the LL data into a new suite of tools called OpenDroneMap (http://opendronemap.github.io/odm/). Its true that the sensor poses somewhat of a challenge in that its real-time sensitivity seems to make it a better candidate for Arduino while at the same time its heavy RAM usage would make it better for the RPi... I'm thinking it will be worth testing it out on the RPi A+, possibly in conjunction with the camera module, first... But if the GPIO proves insufficient then I suppose this is the kind of thing the Beaglebone Black was supposed to be good for... I'll be documenting my results at the following wiki if others are interested- http://publiclab.org/notes/code4maine/0 ... cost-lidar

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jbeale
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Re: Raspberry Pi 3D mapping with radar

Wed Jul 22, 2015 6:28 pm

By the way there is a new "blue label" version of Lidar-Lite (slightly more expensive) that does 500 Hz readings, instead of 100 Hz. I don't have one myself. http://pulsedlight3d.com/

neelesh1121
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Re: Raspberry Pi 3D mapping with radar

Tue Dec 12, 2017 6:16 pm

Hlw, I am using lidar lite v2 sensor with raspberry pi 3 model B for distance measurement. I have used the python code of github https://github.com/Sanderi44/Lidar-Lite, but i am getting 0 output.
I have checked my connection properly.
I have also used C(WiringPi) library given in the sparkfun site, by using this i am getting 0 output.
Lidar lite v2 is working properly with arduino. Please anyone can explain, what can be problem.

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jbeale
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Re: Raspberry Pi 3D mapping with radar

Tue Dec 12, 2017 9:50 pm

the V1 version of the Lidar Lite had a buggy I2C implementation that would hang up at random times, and that was using Arduino-style microcontrollers that have repeatable timing at the microsecond level. See for example https://forum.pjrc.com/threads/28036-Tr ... #post70215

Are you are connecting the lidar-lite I2C lines directly to the RPi? As far as I know the RPi has variable and significant latencies on the GPIO that all general-purpose Linux systems do (unless you disable all interrupts) so I would expect getting reliable results might be harder.

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