As to SUV .... given that some vehicles now have heated front screens with embedded wiring ... also are usually laminated along with mesh in upper centre area ... that fact alone can create reduced signal reception of the cars GPS. Depending on where mounted / antenna etc. and funny enough how dirty / wet that already reducing screen can be ...

But TBH ... the average car GPS and the DJI may use same systems but are mounted and working in different environments.

Quite often when I start up my car at front of the house - it can take a while for Satnav to sort out ... but if I move a few feet back - it sorts quick. Even though there is very little difference in skyview.

Second ... a car GPS is like many other consumer sets - if you move from its switched off position and then switch on .. it goes into Cold Start mode ... meaning it takes a lot longer. It does not need to be a big distance moved sometimes.  It is interesting that the general GPS module used in Multi Rotors such as DJI have a very short Cold Start mode time .. in fact its as if they don't have it all !!

Nigel

Labroides Posted at 2018-10-4 21:09
Forget overcast.
It really, really, really has nothing to do with your observations.
Your map doesn't come from GPS, it comes from the internet.

Those few dB of attenuation from water vapor can make a difference if reception was marginal. It would be quite the coincidence if "other factors" were at play EVERY time the GPS in our SUV has a long delay on a cloudy day and a short delay on a sunny day.

I can get home point updated on a sunny day and even without internet. I just don't get a map, but I get the flight path and the "H" in the blue circle. I've flown like that a number of times. But this is different--I am not seeing a flight path, so it is only possible to tell where the drone is by visual.

Mark Weiss Posted at 2018-10-5 07:01
Those few dB of attenuation from water vapor can make a difference if reception was marginal. It would be quite the coincidence if "other factors" were at play EVERY time the GPS in our SUV has a long delay on a cloudy day and a short delay on a sunny day.

I can get home point updated on a sunny day and even without internet. I just don't get a map, but I get the flight path and the "H" in the blue circle. I've flown like that a number of times. But this is different--I am not seeing a flight path, so it is only possible to tell where the drone is by visual.

Really, forget the whole cloudy day idea.
Despite your theory, users all over the world have no problem with GPS in any weather.
if it was a factor, you would find thousands of people complaining about it.
You'd find planes and ships having to stop and wait when it's overcast.
It makes no difference.
Really.

Labroides Posted at 2018-10-5 13:11
Really, forget the whole cloudy day idea.
Despite your theory, users all over the world have no problem with GPS in any weather.
if it was a factor, you would find thousands of people complaining about it.

It makes no difference as long as the AGC in the receiver is able to compensate enough to keep a level signal. I'm telling you a scientific fact: water attenuates high frequency RF signals. In most cases, not enough to affect most GPS receivers. There may be other factors, however I see a consistent correlation with the nav system in our SUV and weather conditions, as well as the appearance or lack of a home point and flight path with DJI Go 4 software. Clear days, I get a flight path when I fly. Cloudy days, I get nothing and can only tell where the AC is by visual.

It looks like facts just aren't your thing.
GPS works in ANY WEATHER for everyone else in the world but drops out on cloudy days for just you.
GPS must be the problem.

Lack of a home point ???
You've seen from your flight data that you had a home point eeven though you thought you didn't.
Your comment about flight path makes no sense.

Labroides Posted at 2018-10-5 14:57
Lack of a home point ???
You've seen from your flight data that you had a home point eeven though you thought you didn't.
Your comment about flight path makes no sense.

I think he's talking about the lines on the map that show the flight path the drone has flew. Sounds like he is saying he doesn't get that either so he can't follow the path back to the homepoint.

If he wants that feature, all he has to do is enable it in his app settings.

fansb1fe1104 Posted at 2018-10-5 15:23
I think he's talking about the lines on the map that show the flight path the drone has flew. Sounds like he is saying he doesn't get that either so he can't follow the path back to the homepoint.

OP is obviously coloring his experience to fit his argument.  No mention has been made about the LOS issue (relative to the horizon) with the GPS satellites and other surface-fix satellites, which is constantly changing.

Radio waves don't move like a laser beam.  Radio waves bend, and depending on the frequency, can move around, through, and even deflect off rain droplets, water vapor droplets, etc.  And depending on the transmitter's position and the receiver antenna's position, a little rain and fog can actually be advantageous to radio reception.  This is especially true of radio waves in the 1.55 - 1.6  ghz bandwidth, which is obviously why that bandwidth was specifically chosen for GPS.  

I still say this falls under the "operator confusion" category, as mentioned earlier.  

Case in point below (rainy winter morning flight, no rain gear, battery pre-warmed, stock max range 2500', no mods to 4-years-old archaic P2, see # of GPS sats upper right of screen which does not include glonass, note that as the rain became heavier, the satellite # increased):

Labroides Posted at 2018-10-5 14:57
Lack of a home point ???
You've seen from your flight data that you had a home point eeven though you thought you didn't.
Your comment about flight path makes no sense.

Do you have a reading comprehension problem? I said no flight path appears and no home point appears on the map in DJI Go 4. This has happened consistently on overcast days. I can't tell, using the app, where the drone is relative to me when that happens. The last few clear days I flew, I had a flight path and a home point on the map screen and could tell where the drone was, even if the trees obscured my view.

As for GPS, any HAM radio General Class or better knows that the higher the frequency, the more line of sight RF propagation becomes. You look like a complete fool telling a retired broadcast engineer with an ASEE degree that "GPS never has trouble with weather". UHF RF experiences attenuation when it passes through moisture vapor, leaves, or any other materials in its path.

Mark Weiss Posted at 2018-10-6 06:26
Do you have a reading comprehension problem? I said no flight path appears and no home point appears on the map in DJI Go 4. This has happened consistently on overcast days. I can't tell, using the app, where the drone is relative to me when that happens. The last few clear days I flew, I had a flight path and a home point on the map screen and could tell where the drone was, even if the trees obscured my view.

As for GPS, any HAM radio General Class or better knows that the higher the frequency, the more line of sight RF propagation becomes. You look like a complete fool telling a retired broadcast engineer with an ASEE degree that "GPS never has trouble with weather". UHF RF experiences attenuation when it passes through moisture vapor, leaves, or any other materials in its path.

Mark ... I've been trying to avoid saying it but you really are the one that is a complete fool.
Depite your previous career experience and education, you really are getting simple things very wrong.
At least I can fly my Phantom on overcast days or navigate a yacht in a tropical downpour.
But then so can everyone else (except you).


Think about it.
Why would it be that you are the only person in the world for whom, GPS doesn't work on cloudy days?

Making any effort to explain anything to you is totally wasted.

Although some atmospheric conditions like rain or snow can weaken the GPS signal, they generally do not affect GPS reception..

As for weather fronts (warm or cold), this would be an interesting read

And ... because GPS does not just take each iteration and pump out data ... it actually averages data to try and even out anomalies.

On my Yachting GPS / Plotters ... I have a number of them, I can even have option to alter the averaging rate ...

Generally GPS data that is out of accepted range or incomplete ..... is ignored by the controller receiving it.

And again I agree with others - as a professional navigator and user of not only commercial, hobby and military grade GPS units. The GPS signal is 'all weather' capability. The only items I know that can affect it and cause service errors (over fractions of time I might) is : Severe electrical storms and or severe sun spot activity. We will ignore operational suspension by the ground controllers ...

Nigel

solentlife Posted at 2018-10-6 22:02
And ... because GPS does not just take each iteration and pump out data ... it actually averages data to try and even out anomalies.

On my Yachting GPS / Plotters ... I have a number of them, I can even have option to alter the averaging rate ...

Not to mention the inadvisability of comparing experiences between an automobile GPS device and the one fitted to the Phantom. A car GPS is usually a box that is fitted by a mount inside a tin box, being the car. Having been built to a low price, it will have a very average GPS receiver in it compared to the Phantom. The GPS module in the Phantom is a relatively high spec unit with ceramic antenna system and upper level processing, fitted in the top of the aircraft under a thin plastic cover. And for that reason it performs a lot better than most car GPS units.

Geebax Posted at 2018-10-6 22:42
Not to mention the inadvisability of comparing experiences between an automobile GPS device and the one fitted to the Phantom. A car GPS is usually a box that is fitted by a mount inside a tin box, being the car. Having been built to a low price, it will have a very average GPS receiver in it compared to the Phantom. The GPS module in the Phantom is a relatively high spec unit with ceramic antenna system and upper level processing, fitted in the top of the aircraft under a thin plastic cover. And for that reason it performs a lot better than most car GPS units.

Dont many car gps's have the aerial on the roof? My laguna has, as did my older 2002 laguna

Bashy Posted at 2018-10-6 22:48
Dont many car gps's have the aerial on the roof? My laguna has, as did my older 2002 laguna

They can have a roof mounted antenna if it is a factory fitted option, but many people still use a separate device that has the antenna in the device itself. And the portable ones do not have any ability to attach an external antenna.

Mark Weiss Posted at 2018-10-4 18:44
The GPS system is supposed to be transparent, but that doesn't mean signals are not attenuated by water vapor. 1575MHz is conveniently between the GSM cellular and PCS cellular bands. There is nothing magical about that frequency.

There is no user confusion about using the GPS. Either it locks on or it doesn't. I can only state that our SUV's GPS takes a lot longer to lock on in cloudy weather than it does on clear days.

"I do see that the log shows home point recorded 3.3 seconds after motor start. The question is why it didn't show up on the tablet screen as it normally does."

Can you try a different tablet or reinstall DJI Go 4 App' on your display device ?

Given the flight record you've provided, the GPS looks good and home point recorded. The problems seems to be how that information is being displayed.

Geebax Posted at 2018-10-6 22:54
They can have a roof mounted antenna if it is a factory fitted option, but many people still use a separate device that has the antenna in the device itself. And the portable ones do not have any ability to attach an external antenna.

AND that some cars that people think haved GPS antenna on the roof are actually mistaking the GSM relay antenna .....

But it still does not change fact that GPS is basically all weather with very little restriction.

Nigel

Apparently one person here has never used an in-dash automobile GPS, because in reality, there is no "operator error" because it is a turnkey system. The time to acquire satellites is dependent on the quality of the receiver, antenna and weather conditions. The operator simply puts the key in the ignition switch and drives the car. The GPS satellite acquisition is automatic and not subject to "user error".

That was a very interesting read and backs up what I have already said about atmospheric conditions. A quality receiver will make weather conditions transparent, as it's AGC on the analog side of receiving the RF signals, as well as the algorithms that compensate for the various delay factors, handle all the heavy lifting and in the end, you have GPS information. That may not be the case for the one in our SUV. As I have observed, it acquires in about a minute on a clear day, in my driveway, with trees around, but on heavy overcast and rainy days, I have driven as long as 45 minutes on the open highway before the vehicle's position finally updated and enough satellites were acquired. Someday, we need to buy a newer vehicle, though our impending move to Japan is holding off vehicle purchases.

Aardvark correctly points out that this is really a display problem. What needs to be discovered is why the Crystal Sky Ultra has been consistently failing to provide a flight path in the map window and a home point after takeoff. The times I have flown on clear days, this always happened just after motor start, before takeoff. My last three flights have been under overcast conditions with light precipitation starting and none of those flights displayed a flight path nor a home point on the map window. I'm waiting for another clear day to see if the flight path displays, but so far with have been stuck in a perpetual rain cloud since August.

I have a hunch it's a timing issue. The tablet might not update it's flight map if GPS isn't acquired within a certain window of time and if the acquisition happens just outside that limited window, it never updates the display. That's my postulate for what may be causing this behavior. Unfortunately, nothing in the logs reports on how the tablet device behaves with regard to displaying or not the flight path.

If I had a 45 min no show .... I'd be really p'd off ....

Something must be wrong with the gear or setup ...

Nigel

solentlife Posted at 2018-10-7 09:10
If I had a 45 min no show .... I'd be really p'd off ....

Something must be wrong with the gear or setup ...

Yeah, it's annoying, especially when we need it for a long trip to New York.. we get almost halfway there sometimes before the thing acquires enough satellites and the navigation instructions start. It's bad enough driving on an interstate with heavy rain and accidents every ten miles or so mucking up the works, but flaky GPS adds to the tension.

Mark Weiss Posted at 2018-10-7 10:01
Yeah, it's annoying, especially when we need it for a long trip to New York.. we get almost halfway there sometimes before the thing acquires enough satellites and the navigation instructions start. It's bad enough driving on an interstate with heavy rain and accidents every ten miles or so mucking up the works, but flaky GPS adds to the tension.

I'd replace with a good set ... there's no way a GPS should take that long ...

The only time I have a long acquisition time is when I power up and drive away before its completed sat locks. But it never takes more than a minute or so ..
Bit like trying to hit a golf ball while its moving ...  

Nigel

Mark Weiss Posted at 2018-10-7 08:51
Apparently one person here has never used an in-dash automobile GPS, because in reality, there is no "operator error" because it is a turnkey system. The time to acquire satellites is dependent on the quality of the receiver, antenna and weather conditions. The operator simply puts the key in the ignition switch and drives the car. The GPS satellite acquisition is automatic and not subject to "user error".

That was a very interesting read and backs up what I have already said about atmospheric conditions. A quality receiver will make weather conditions transparent, as it's AGC on the analog side of receiving the RF signals, as well as the algorithms that compensate for the various delay factors, handle all the heavy lifting and in the end, you have GPS information. That may not be the case for the one in our SUV. As I have observed, it acquires in about a minute on a clear day, in my driveway, with trees around, but on heavy overcast and rainy days, I have driven as long as 45 minutes on the open highway before the vehicle's position finally updated and enough satellites were acquired. Someday, we need to buy a newer vehicle, though our impending move to Japan is holding off vehicle purchases.

If I was sitting in the car beside you with a Garmin handheld GPS, it would have full GPS reception within a minute if you were driving out in the open.
You have a faulty GPS unit or a faulty installation.
Weather doesn't have any detectable effect of GPS.
While you stick with the false theory of weather being involved, you'll never solve the issue.

Geebax Posted at 2018-10-6 22:54
They can have a roof mounted antenna if it is a factory fitted option, but many people still use a separate device that has the antenna in the device itself. And the portable ones do not have any ability to attach an external antenna.

Sorry, i read you say "automobile gps" and took that as you meaning factory fitted,

My Laguna does not like removable sat navs, such as my Nnote 5 using Waze, it can sometimes take an age to get a lock and sometimes its at the end of the journey, it doe snot have electric scren but i think it does have a purple tint to the screen screen, never realised the screen could be the issue

solentlife Posted at 2018-10-7 05:02
AND that some cars that people think haved GPS antenna on the roof are actually mistaking the GSM relay antenna .....

But it still does not change fact that GPS is basically all weather with very little restriction.

My lagunas deffo have the aerial on the roof, it even says gps on the aerial, unless of course, Renault spelt GSM wrong, its French after all I also think that you may find that if the manufacturer puts a GSM  antenna on the roof, it will also include the GPS as well, kill 2 birds an all that

Mark, It only takes a seconds to ask Mr Google and you will find that whilst weather (water vapour) can have some affect, the affect its so small its plays no part, the GPS still locks on.

As to why mine takes much longer, 2 maybe 3 times longer to acquire a lock for the home point (normally 8 upwards i think it is)  compared to my mates mavic is beyond me,  Luck of the draw i suppose,  perhaps there is some issue with your cars GPS antenna, be it internal or external?

Bashy Posted at 2018-10-7 19:32
My lagunas deffo have the aerial on the roof, it even says gps on the aerial, unless of course, Renault spelt GSM wrong, its French after all  I also think that you may find that if the manufacturer puts a GSM  antenna on the roof, it will also include the GPS as well, kill 2 birds an all that

I said SOME ...... and I was not implying YOU were wrong with the Laguna.

Back to screens - most cars today have laminated screens ... and some have a different layer in the sandwich to not only strengthen the screen, but also to reduce heat transfer. You may not see any difference - but that material may and does on some vehicles have an affect.

My Volvo ... if I place my TomTom in the upper centre section of my screen - I have poor reception, not because of the roof line - but because of the sunstrip that runs along the top ... only in certain angled light can you see it.
My Volvo is not only vehicle with this.
Imagine a vehicle with its screen much larger heat stripped !

Nigel

solentlife Posted at 2018-10-7 21:06
I said SOME ...... and I was not implying YOU were wrong with the Laguna.

Back to screens - most cars today have laminated screens ... and some have a different layer in the sandwich to not only strengthen the screen, but also to reduce heat transfer. You may not see any difference - but that material may and does on some vehicles have an affect.

It was the implication considering you mentioned that after my reply ;)

I beleive my laguna has some sort of layer that is causing reception issues for my phone, you can see a purple colour to the screen when looking at it from the outside, i am going to assume this is the very reason from the roof mounted antenna and why my phone struggles...

Bashy Posted at 2018-10-7 21:17
It was the implication considering you mentioned that after my reply ;)

I beleive my laguna has some sort of layer that is causing reception issues for my phone, you can see a purple colour to the screen when looking at it from the outside, i am going to assume this is the very reason from the roof mounted antenna and why my phone struggles...

And is why some cars have the GSM blob ... which can look similar to GPS blob.

The Heat/ Sun strips in screens are usually of metallic compound.
Don't forget also that many cars today have their radio antenna embedded into that screen ...

Nigel

solentlife Posted at 2018-10-7 22:12
And is why some cars have the GSM blob ... which can look similar to GPS blob.

The Heat/ Sun strips in screens are usually of metallic compound.

I know the older lagunas mk2 < had aerial in the rear heated window so it would only make sense for people like ford that have the heated front screen to use that for the aerial, saves on coax if not else... FOr my laguna, i dare say its the tint in the screen thats causing the issue, i do know that when you replace the back window you can choose the tinit on non tint, might be an option for me to unluckily accure a giant bullseye right in my line of vision ;)

Bashy Posted at 2018-10-7 19:48
Mark, It only takes a seconds to ask Mr Google and you will find that whilst weather (water vapour) can have some affect, the affect its so small its plays no part, the GPS still locks on.

As to why mine takes much longer, 2 maybe 3 times longer to acquire a lock for the home point (normally 8 upwards i think it is)  compared to my mates mavic is beyond me,  Luck of the draw i suppose,  perhaps there is some issue with your cars GPS antenna, be it internal or external?

It's a Kenwood system complete with radio, DVD/CD player and Garmin GPS. The antenna is on the dash at the base of the windshield.

Mark Weiss Posted at 2018-10-10 13:01
It's a Kenwood system complete with radio, DVD/CD player and Garmin GPS. The antenna is on the dash at the base of the windshield.

'The antenna is on the dash at the base of the windshield.'

That is not a good place for reception, as the roof would shadow the antenna for nearly 180 degrees.

Geebax Posted at 2018-10-10 15:44
'The antenna is on the dash at the base of the windshield.'

That is not a good place for reception, as the roof would shadow the antenna for nearly 180 degrees.

I wouldnt say that was the issue Geebax, prob going back to something  in the glass being the issue, The base of the windSCREEN ;) should be more than ample, my Note 5 works in other vehicles just fine and it sits half way up the windscreen, being halfway up would see a bit less of the sky than Mark's, not only that Most aftermarket GPS are stuck halfway up the windscreen ;)  and thats with a tiny inbuilt antenna, Marks is laid along the dash at the base thus having a larger antenna area and seeing more of the sky, thats my thoughts anyway, ive only got experience in using them, no expert knowledge

I flew today, the first sunny day we've had in about a month, and guess what? The home point updated within seconds of the drone acquiring GPS. I was on a picnic bench under a tree, too. Go figure..

Mark Weiss Posted at 2018-10-20 13:48
I flew today, the first sunny day we've had in about a month, and guess what? The home point updated within seconds of the drone acquiring GPS. I was on a picnic bench under a tree, too. Go figure..

The home point updated within seconds of the drone acquiring GPS.
Just like it does on any other day in any other weather.
That's how it works.

Labroides Posted at 2018-10-20 14:33
The home point updated within seconds of the drone acquiring GPS.
Just like it does on any other day in any other weather.
That's how it works.

"Supposed to work." I know correlation does not imply causation, but I am seeing a pretty consistent track record here.

Mark Weiss Posted at 2018-10-20 15:55
"Supposed to work." I know correlation does not imply causation, but I am seeing a pretty consistent track record here.

But no-on else does.
GPS works for everyone else in any weather, just as it is designed to.

And you've shown flight data that proved your Phantom records the home point quickly even in overcast weather.

Labroides Posted at 2018-10-20 22:16
But no-on else does.
GPS works for everyone else in any weather, just as it is designed to.

The unexplained part is still why the Go4 software doesn't display a home point only on cloudy days, but does so quickly on clear days. Sounds like a timing window issue in software (if home point not recorded in X time period, ignore, etc).

Today was the first time under predominantly clear skies that I started up my P4P and didn't get a home point or a map display. I made sure I had a wi-fi signal too, as confirmed by the change of status "firmware up to date" changed to "firmware update required". But still no map, no path and no home point. So since my "mission" was to fly about 1800' to observe some construction up the road, I wasn't too comfortable flying over the tree boundary, as a disconnect would be problematic. Fortunately, the system didn't experience any glitches (the Crystal Sky has been reliable since the temperatures dropped) and I was able to fly home by FPV, following the road below as a guide.

But I really want to know why the heck I'm not getting a path showing where the drone is and where Home is much anymore. In the spring, I would see these navigation guides without fail. Now they rarely appear on my screen.

Mark Weiss Posted at 2018-10-23 14:04
Today was the first time under predominantly clear skies that I started up my P4P and didn't get a home point or a map display. I made sure I had a wi-fi signal too, as confirmed by the change of status "firmware up to date" changed to "firmware update required". But still no map, no path and no home point. So since my "mission" was to fly about 1800' to observe some construction up the road, I wasn't too comfortable flying over the tree boundary, as a disconnect would be problematic. Fortunately, the system didn't experience any glitches (the Crystal Sky has been reliable since the temperatures dropped) and I was able to fly home by FPV, following the road below as a guide.

But I really want to know why the heck I'm not getting a path showing where the drone is and where Home is much anymore. In the spring, I would see these navigation guides without fail. Now they rarely appear on my screen.

I'm not sure if this has been covered already, but you do have 'Show flight route' enabled in 'General Settings' menu ?
Also 'Cache Map in the Background' might help.

(I'm assuming that CS version of 'Go 4' has these function switches)