Has anyone tested the VL53L1X to measure pastures? (pointing down, outdoors, with sunlight from 14 to 93.6 klux)

[Eugênio PIerazzoli]

I´m using multiple sensors for distance ( 3 VL53L1X, 1 HC-SR04, 1 TFMini Plus). 

I think I need a lot of coverage to shade the measurement point and thus reduce the light to 140 lux (stable in the lab).

I tried to switch to short mode and time budget to 200ms but that didn't solve my problem.

In the laboratory, the TF mini Plus (850nm) did not generate interference on the VL53L1X (940 nm VCSEL).

I ran the experiments for 3 days over several hours, collecting 8622 + 5450 + 1540 measurements, with only 33% useful data from the VLs, 89% from TF and 95 from HC-SR04.

Does anyone have a better idea?

Looks like the VL53L1X is from "Wayne Enterprises, Inc." It's made for Batman... high tech, exclusive use in the dark. :> I like the features of the VL53L1X. Low cost, low consumption, small size and high sensitivity.

[John E KVAM]

It really is an indoor sensor - or at least a shade sensor.

Is there anyway you can take these measurements at night?

Or supply your own shade?

The sensor would work very well from the underside of a truck.

(Not sure if your wheels are a mock-up of your final vehicle or just part of your test setup.)

There is one New Zealand company building a pasture monitor. But it only ranges at night.

• john

[Julien NGUYEN]

Hello Eugenio,

I love your illustrated pictures. It makes me traveling for few seconds in another place.

Actually, it is not fair to compare the VL53L1X with the HC-SR04 in outdoor condition, because the L1X is light based sensor (sensitive to the sunlight) while the HC-SR04 is based on the ultra-sound which doesn't care the ambient light. What is the TF mini Plus (850nm) ?

Thanks,

Julien

[Eugênio PIerazzoli]

Hello John!

1 - It is desirable that the equipment operate autonomously 24 hours a day, except when it rains or there is dew on the plants.

2 - This week I'm going to run experiments restricting side light that can cause an error on the VL53L1X. A future idea is to use the solar panel shadow over the sensor bar and measurement site.

3 - Here at the Federal University of Pampa (Brazil), in my graduate program I am creating an automated system for weed removal based on equipment from my advisor (Campo Limpo Grazmec), which uses wet ropes applying the herbicide (non-selective) by contact only in the weeds. It is efficient, but still highly dependent on the operator's herbicide dosage adjustments, in fields that can have a wide range of infestation level and travel speed limitation.

Another line of research is to provide telemetry to estimate plant biomass through neural networks, where georeferenced pasture height data provide one of the variables to feed systems (also uses satellite photos, rainfall history, relative humidity, wind and solar radiation) to predict pasture growth and indicate the number of animals per hectare.

4 - I follow companies in New Zealand that do weed control in a very similar way. They have the same problem as here in southern Brazil, the popular name is "Capim Annoni / African Love Grass" for "Eragrostis Plana Nees".

Thanks for listening!

[Eugênio PIerazzoli]

Hello Julien!

The idea is to have multiple sensors that use different physics and different operating frequencies.

In the laboratory, the HC-SR04 did not do well because of the structure of the weed "Eragrostis Plana Nees" and the low sensitivity or ability to measure this type of object.

I tested the L0X, and it didn't get a good read rate, except at some angles. The L1X, on the other hand, proved to be very promising due to its sensitivity. I also studied articles with the spectrometry of "Eragrostis Plana Nees" and it presents a high reflectance for these two bands.

The last one was the ToF sensor tfmini plus by Benewake, but it is comparatively expensive and the consumption is high (140 to 200 mA ), serving more as a comparison in the experiments.

Thanks,

Eugênio Pierazzoli

These photos are in southern Brazil, on the border with Uruguay.

(Google Street View 2011)

https://www.google.com/maps/@-31.3059447,-54.065404,3a,90y,151.25h,102.11t/data=!3m7!1e1!3m5!1sSdUYc2LkDTjTah3E8LNDfg!2e0!6selshttps:%2F%2-Fstreetviewpixs .googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DSdUYc2LkDTjTah3E8LNDfg%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D2.2080903%D266316pitch!3ditch!

[John E KVAM]

if you need a solar panel, then just put the sensor under the panel. Unless you get really far above the field I'll bet the panel will shade the sensor enough to make it work. The problem is ambient light. Sunlight has a large component of 940nm and that saturates the sensors photon detector. But pointing the sensor down at surface that is neither very reflective or very mirror-like (non-specular) is good and shading the surrounding area is even better. I'm betting it will work just fine.