Weird altitude issue

SparkyNate · Mar 3, 2019

Hello all,
I was flying my spark today in 9 degree weather here in Wisconsin,I was at 150-200 feet the whole time and I noticed that every 10 -15 seconds my altitude would flash from 200 feet too 10 or so feet and it would show the icon indicating it was measuring using the downward sensors? Flight was flawless otherwise,sensors are all clean and nothing is blocking them,it was very sunny and I was flying over snow,I thought maybe a reflection was causing this? I don’t really know how the downward sensors operate. I searched extensively and could not find the same issue. Thanks in advance for any input and have a great weekend!!

Andre Levite · Mar 3, 2019

The Spark:s altitude is primarily calculated by an on-board barometer. There are two types of downward facing sensors: a camera to record the precise takeoff spot for RTH and ultrasonic sensors to detect the ground at low altitudes.

I suspect your issue is related to reflections from the snow hitting the US sensors. We don't have snow here in Florida but I get often get aberant sensor readings due to reflections when flying over completely still water.

It would certainly be easy to test this theory by flying over ground that is free of snow. I hope you can find some!

nilanjan118 · Mar 3, 2019

I had the same experience once and as mentioned in comment #2, it is certainly due to reflection from snow or fog/mist.
Earlier in the month of February, I was flying over a vast open field completely covered with snow and suddenly started getting aberrant altitude information. Later when I checked my flight log, I found that the bottom sensors were continuously going crazy at about 150 feet. I have done several flights thereafter and never found such error again. So nothing to be alarmed about.
Here is a screenshot from my flight log. I am sure your's will have a similar pattern.

Stever68 · Mar 18, 2019

I am in Florida as well and I continually get the altitude error. Once I am above 10-15 feet the altitude readout will continuously bounce between actually altitude and somewhere in the single digits. It doesn't matter if I am flying over land or water. It's annoying, but doesn't seem to effect the fly ability of the spark. But I always have that thought in the back of my head, if it can't even read altitude correctly what else is going to go wrong?

Paul215 · Mar 19, 2019

Do you have a skin attached? I had this problem after installing a decal. The three holes a the bottom were free but the foil was too shinny for the sensor. The spark VPS sensors work with infrared not ultrasonic (mavics, phantoms) what makes them really sensitive.

In an other case I read from someone who had moist INSIDE the sensors.

Stever68 · Mar 19, 2019

No I have no decals on the drone. I always hear about people leaving the stickers on the sensors when they first get the drone, but mine did not have any protective stickers when I unboxed it.

Marcel Campos · Apr 8, 2019

Stever68 said:
No I have no decals on the drone. I always hear about people leaving the stickers on the sensors when they first get the drone, but mine did not have any protective stickers when I unboxed it.

Hey Stever68, did you solved the VPS issue? My Spark has the same problem... and now it's in a drone repair center, probably the VPS sensor came defective... here in Brazil there's some cases with brand new out the box Spark drones with the same problem

Stever68 · Apr 9, 2019

Marcel Campos said:
Hey Stever68, did you solved the VPS issue? My Spark has the same problem... and now it's in a drone repair center, probably the VPS sensor came defective... here in Brazil there's some cases with brand new out the box Spark drones with the same problem

No my Spark still does this on occasion. I started to send it back in but decided not to, I just didn't want to be without my drone for that long. Please let me know how long it takes to get yours back and if they successfully repair it. I may still send mine back

flickinfritz · Apr 9, 2019

Stever68 said:
Once I am above 10-15 feet the altitude readout will continuously bounce between actually altitude and somewhere in the single digits.

Rebar in cement can cause this.

Andre Levite · Apr 9, 2019

flickinfritz said:
Rebar in cement can cause this.

Are you positive about that?

While it is well-known that ferrous metals such as re-bar can wreak havoc with a compass I have heard no such effect on the Spark's on-board barometer (or altitude reading).

The Spark calculates altitude based on changes in atmospheric air pressure -- exactly how is a piece of metal going to effect the barometer or alter atmospheric pressure?!?

Marcel Campos · Apr 10, 2019

Stever68 said:
No my Spark still does this on occasion. I started to send it back in but decided not to, I just didn't want to be without my drone for that long. Please let me know how long it takes to get yours back and if they successfully repair it. I may still send mine back

Probably 'till friday the people from the repair center will give me an solution for the issue - but they told me that another Spark has a similar issue, but he also was bouncing when close to the floor nad in this case the IMU replacement solved the problem.
As my Spark it's already out of warranty (I bought it on february 2018), it's not with DJI, but an authorized repair center.
As soon as I get an position about it, I'll let you know.

Putz · Apr 10, 2019

When I had my spark, it would occasionally do this. When ever it happened I returned to my location, powered down, cleaned the downward sensors, resumed my flight with no issues. This would happen once or twice a month. My theory is that I hand caught a lot and I would smudge the sensors with my hands and it would give false readings while flying. If I remembered to wipe the sensors prior to flight, I never had the issue come up. Hope this helps.

nilanjan118 · Apr 11, 2019

Putz said:
My theory is that I hand caught a lot and I would smudge the sensors with my hands and it would give false readings while flying. If I remembered to wipe the sensors prior to flight, I never had the issue come up.

Interesting theory. I recently watched a YouTube video regarding hand catching the Spark and flipping it over to shut the motors. The guy in the video suggests the best way is to make the drone facing you sideways. That way you precisely know where the bottom sensors are and don't trigger them making the drone move up and away from you. Also, the length (body) of the drone facing you laterally makes the grip more natural. I think everyone who like to hand catch the drone should follow this.

Paul215 · Apr 11, 2019

The spark is using infrared vps sensors. They are much more sensitive then the ultrasonic sensors from the mavics and phantoms. I attached a skin on my spark and the 3 holes on the bottom were defently free but I got a altitude problem. I think the problem was that the foil was to shiny. After removing the foil in this area the problem was gone. In this forum and also on some Facebook sides I read a lot about VPS problems. Always due to different reasons. (landing gear, decals, fingerprints, water drops, moist inside the sensor, stuff attached under drone, fog, high air moisture,.....)

Marcel Campos · Apr 11, 2019

Stever68 said:
No my Spark still does this on occasion. I started to send it back in but decided not to, I just didn't want to be without my drone for that long. Please let me know how long it takes to get yours back and if they successfully repair it. I may still send mine back

Hey Steve, the repair center have found the problem: the VPS sensor is fault.
One year ago, when I start using the Spark, I select the auto landing and due to low light / magnetic interference, the Spark descend too fast and bounced the floor, and land... and was after this day the VPS sometimes has the error, but after one year this issue became intermitent...

They have replaced the VPS sensor and it's perfect again.... I'll pick it up tomorrow probably...