Coverage gaps using Drone Deploy, Pix4D, GS PRO

[rdavis103]

I have 2 P4P v1's and have been doing mapping/inspections using DroneDeploy or Pix4D or GS Pro.
I've been getting gaps in the coverage when I plot the captured images over the top of the subject property.
For example if I take 300 photos at 100' altitude there will be up to 8 gaps where there is no image when plotted onto the subject property.
The images will be consecutive (183, 184, etc) but between 183 and 184 is open space.
I've tried slowing way down in DroneDeploy to 3mph which helps but doesn't eliminate the issue and takes forever to fly.
I've tried tweaking every setting I can see in Pix4D and GS Pro also.
Does anyone have experience with this or success resolving??

 

[Meta4]

if I take 300 photos at 100' altitude ...
I've tried slowing way down in DroneDeploy to 3mph

I used to get occasional missed single images, but never enough to cause a problem.
!00 feet is very low for mapping missions.
Is there any particular reason for that?
You should be able to map at 20+ mph

 

[Dave Pitman]

I've been getting gaps in the coverage when I plot the captured images over the top of the subject property.

The P4P is known for this. As far as I know, the cause has never been determined. Like @Meta4 suggested, typically, 100' agl would be considered at the low end of flight height for good coverage. That said, you should be able to increase your overlap to negate any negative effect caused by the image gaps.

Remember that your overlap settings are based upon the mission height to the take off point. If you have 70% selected, but have some objects that are 15' tall, the overlap on those objects will be less than 70%. This problem is more sensitive when flying at lower heights like you are doing.

 

[ArnoldLeVine]

When you say mapping/inspections, are these two different outcomes?
If you notice in Drone Deploy, the default height for orthomosaic mapping is 250 ft. Try it out, or at least 200 ft. You will need fewer photos, less time, you can fly faster as there will be less camera movement blur, and of course, I'm sure you have mechanical shutter turned on. The only gaps I find this way is under eaves overhangs, etc. which can be fixed with some low level 45 degree or even zero degree gimbal shots added in.

If it is for roof or other inspections, then the low height for super resolution is more appropriate. In which case you might want to do a cross pattern with even more shots. do you have an example of a problem you can share?

 

[Dave Pitman]

When you say mapping/inspections, are these two different outcomes?
If you notice in Drone Deploy, the default height for orthomosaic mapping is 250 ft. Try it out, or at least 200 ft. You will need fewer photos, less time, you can fly faster as there will be less camera movement blur, and of course, I'm sure you have mechanical shutter turned on. The only gaps I find this way is under eaves overhangs, etc. which can be fixed with some low level 45 degree or even zero degree gimbal shots added in.

If it is for roof or other inspections, then the low height for super resolution is more appropriate. In which case you might want to do a cross pattern with even more shots. do you have an example of a problem you can share?

The OP's question is in regard to missing images in grid pattern missions. If you do fly these types of missions using a P4P and don't have gaps, I'd love to see your image spacing report.

 

[rdavis103]

I used to get occasional missed single images, but never enough to cause a problem.
!00 feet is very low for mapping missions.
Is there any particular reason for that?
You should be able to map at 20+ mph

I've been near Class B airspace with 100' limit for most of these inspections so FAA limits. it seems to me that I was not having a lot of gaps in coverage until these

 

[rdavis103]

The P4P is known for this. As far as I know, the cause has never been determined. Like @Meta4 suggested, typically, 100' agl would be considered at the low end of flight height for good coverage. That said, you should be able to increase your overlap to negate any negative effect caused by the image gaps.

Remember that your overlap settings are based upon the mission height to the take off point. If you have 70% selected, but have some objects that are 15' tall, the overlap on those objects will be less than 70%. This problem is more sensitive when flying at lower heights like you are doing.

thank you, thats a good point. i will try higher overlap rate and see how it affects the outcome

 

[rdavis103]

When you say mapping/inspections, are these two different outcomes?
If you notice in Drone Deploy, the default height for orthomosaic mapping is 250 ft. Try it out, or at least 200 ft. You will need fewer photos, less time, you can fly faster as there will be less camera movement blur, and of course, I'm sure you have mechanical shutter turned on. The only gaps I find this way is under eaves overhangs, etc. which can be fixed with some low level 45 degree or even zero degree gimbal shots added in.

If it is for roof or other inspections, then the low height for super resolution is more appropriate. In which case you might want to do a cross pattern with even more shots. do you have an example of a problem you can share?

these are mostly inspections or roofs and pavement/ground, with some general overview mapping

 

[ArnoldLeVine]

How large an area are you mapping?

 

[dewens]

I have 2 P4P v1's and have been doing mapping/inspections using DroneDeploy or Pix4D or GS Pro.
I've been getting gaps in the coverage when I plot the captured images over the top of the subject property.
For example if I take 300 photos at 100' altitude there will be up to 8 gaps where there is no image when plotted onto the subject property.
The images will be consecutive (183, 184, etc) but between 183 and 184 is open space.
I've tried slowing way down in DroneDeploy to 3mph which helps but doesn't eliminate the issue and takes forever to fly.
I've tried tweaking every setting I can see in Pix4D and GS Pro also.
Does anyone have experience with this or success resolving??

Check camera settings you may need to adjust the F stop

 

[ArnoldLeVine]

Check camera settings you may need to adjust the F stop

please explain what the F-stop could have to do with his gaps.

 

[rdavis103]

How large an area are you mapping?

20-30 acres

 

[rdavis103]

I'm going to try a new micro SD card and see if that improves anything

 

[Dave Pitman]

I'm going to try a new micro SD card and see if that improves anything

By all means, give it a try. But it will not solve the problem. Many have tried before you. The strategy that works is to fly with enough overlap so that a few missed captures does not degrade the processor.

 

[rdavis103]

Update: I have been getting *better* but not great map coverage by restarting the device I'm using (iphone/ipad) for the mapping applications immediately prior to flight. previously I had been just closing one app like dji go and then opening a mapping app. there's been consistent improvement with coverage the last few days

 

[rdavis103]

seems much better over the last 6 flights, minimal gaps. I increased overlap a bit to (75-80front/75-80 side), slowed down to 4 or 5 mph depending on altitude, changed SD cards (probably no effect on results), reloaded the mapping software (DroneDeploy, Pix4D, GS Pro), and have been shutting down and rebooting iPhone 12/iPad mini then only loading the mapping program immediately prior to flight.
Thank you everyone for your help!

 

[Kentrol72]

seems much better over the last 6 flights, minimal gaps. I increased overlap a bit to (75-80front/75-80 side), slowed down to 4 or 5 mph depending on altitude, changed SD cards (probably no effect on results), reloaded the mapping software (DroneDeploy, Pix4D, GS Pro), and have been shutting down and rebooting iPhone 12/iPad mini then only loading the mapping program immediately prior to flight.
Thank you everyone for your help!

I was recently made aware that using the wrong SD card could cause gaps due to write speed limitations. Here's a quote on the matter: " One of the biggest causes for missing images, gaps, etc. is due to low-quality SD cards. More specifically, cards with low write speeds. If you're on a budget and just trying to get a card on the low, you may come across some cards that aren't performance centered. Imagine this, a normal drone can map at a max shutter speed of 2 seconds. If an SD card has a write speed of 5-10MB/sec it can cut it really close and sometimes it just bottlenecks and skips an image or two from time to time. To avoid this, you have two choices; fly slower on those cards or grab yourself a higher write-speed card. Personally, I use SanDisk Extreme U3/A2 256GB cards with write speeds up to 130 MB/sec - it's a bit overkill but you will be glad for the number of times you don't have to recapture missing data and speed on through your capture"

 

[ArnoldLeVine]

Micro SD cards have gotten so cheap it's a non starter to use one like the Sandisk Extreme U3/A2 listed mentioned above.
I use the

SanDisk 64GB Extreme PRO on Amazon for $14 each.​

or the

Lexar Professional 1066x 64GB microSDXC UHS-I Card w/ SD Adapter, C10, U3, V30, A2, for $13 each​

I can put 3000 20 megabyte jpgs on one, or an hour of 4k Video, so I have plenty of capacity, and I have several and change after each flight or mission.

 

[ArnoldLeVine]

The OP's question is in regard to missing images in grid pattern missions. If you do fly these types of missions using a P4P and don't have gaps, I'd love to see your image spacing report.

Dave, can you tell me where to find the image spacing report? I'm not familiar with the term. I don't get "holes'" in my mapping with my P4PV2, so I'd be glad to share.

 

[Dave Pitman]

Dave, can you tell me where to find the image spacing report? I'm not familiar with the term. I don't get "holes'" in my mapping with my P4PV2, so I'd be glad to share.

By "report", I just mean the visualization of the camera locations over the ground. (see a sample from a P4P mission in Metashape below).

I'm not saying you will have holes in your results. If you have suffient overlap, the missing images will not effect the results. But there are misses. I have not seen a single P4P mission that did not have these occasional missing images. Other craft do not suffer from this issue. What ever your processor, you should be able to view the camera positions like in my sample. See what you have. Maybe yours is the only one that doesn't miss captures!