Jacko92

Mapping a roof with Olympus 45mm (Inspire 1 Pro) HELP!

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Hi,

Need some help/advise with using 45mm for mapping a roof for inspection - NOT 3D model.

We have been testing DroneDeploy for automated full roof inspections - basically to save us time taking manual pictures which can be difficult when doing sizes such as 10,000 sq ft. We are using the Olympus 45mm, X5 on Inspire Pro.

The picture quality isn't great - they almost look unfocused? We need them really detailed for post analysis for conditions. 

We have had issues previously when flying below 30ft above the structure but on this particular flight we were at 60ft AGL aprox 40ft above the roof and they are still poor quality.

I have no idea why? below are the settings for both DD & the camera.

DD Settings:

Overlap: 90%
Speed: 4 MPH 
Height: 60ft 
Camera: Manual

Camera Settings:

Focus: Infinity (Manual) 
ISO: 100
AP: f/6.3
Shutter: 1/250

Has anyone got any experience doing this or what could be wrong? Or is it simply impossible with this lens for this particular task? Could it be the focus or are we missing something? Surely its not the speed as 1/250 at 4mph is fine. We did fly faster before and had the same issue hence slowed it down.

Thanks in advance!
Jack

Optimized-DJI_0035.JPG

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Thanks very much Kara - I did post this on the Facebook page and on the DroneDeploy forum as well. There hasn't been any responses so I presume this is a tough one? 

Just need it narrowing down - is it calibration or DD settings! 

Really appreciate your help!

Jack 

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Kara also, after just checking DroneDeploy hasn't even processed the Map. I submitted it to see how it would come out for testing and nothing has been stitched together its just the normal google maps type view. 

I will re: submit the images... but not sure if this is a sign that it won't work correctly with DD?

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It's next to impossible to troubleshoot images online on a cell phone but I don't really need to see the image.

Given your altitude, focul length of the lens and the speed of the drone, your shutter speed is way too slow.  For aerial surveys your shutter speed should rarely be below 1/800.  Plus the lower you are the faster your shutter speed needs to be.  

Again I can't tell by looking at this on my phone but I'd be willing to bet that it appears to be in focus, your dragging your shutter and this is motion blur.

I don't know the crop factor of the X5, but it's probably at least 1.6 which makes that at least a 72mm lens.  At 1/250 shutter you'd get motion blur taking the shot hand held on the ground.  

Edited by Av8Chuck

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Hi Av8chuck - thanks very much for the response. 

Would this explain why the images of the roof aren't that great yet the ground shots (over the edge of the roof) look pretty clear? Is it just because we are closer to the roof that you can tell the most? This is why I was thinking its a calibration issue because the ground shots look clearer?

I'll be honest - I had no idea the shutter would need to be that high for a 4mph flight. As mentioned above we flew the same mission with higher shutter and the result was the same however it was nowhere near 1/800. 

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How far is the roof from the ground?  There's is the possibility that this could be a DOF issue, but it's more likely a motion blur issue.

A couple of things you can test.  

Try auto focus.  That's usually only an issue if your taking shots faster than every 2 seconds.

fly higher.  Not sure the resolution of the X5, I'm guessing 16-20MP which should be fine for 100-159ft.

If your restricted to 60ft try a wider angle lens

Obviously faster shutter

Also didn't you mentioned that your not interested in a 3D model?  If not you don't need such high overlaps.  The high overlap is to more accurately determine the z-axis.  

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Thanks for the info.

The roof is roughly 20ft high. DOF issue would be resolved increasing ap?

We can't fly any higher than 60ft as the detail won't be there.. And the same goes for using the 12mm.. It just isn't the right sensor for the inspection level we need. 

I will try high shutter and then auto focus as well If need be. 

Dronedeploy kept missing edges of the roof and not flying straight lines (not sure if this was because there was a breeze) this is why we are going for such high overlap. I guess this again is the difficultly with flying so low over a relatively small object in comparison to normal mapping techniques. My only thought of counteracting this without increasing height is to have really high overlap?

Just to mention as well - I looked backed at some pictures we took the other day manually at 50ft all settings pretty much same as listed above however the shutter was 1/400 and they are much higher quality images especially when zooming which is very important. Okay we weren't flying at 4mph (probably more like 1mph) but this could be the main indicator it's the shutter? 

Thanks again mate. 

 

 

Edited by Jacko92

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Not sure how much you want to debate this and how often you do this type of work but there are alternatives that might be better suited for your application.  

The challenge of using DroneDeploy is partly the accuracy that the drone can fly the path.  In order to have much finer precision you have to be able to tune the flight controller to fly missions well which is very different then tuning a drone to fly well by hand.  Our drones are not fun to fly but in a mission its on a rail so we can shoot with 30% overlap and know we got the level of detail needed.  That's not to say that we do, just that we can if required.

Also, Using only GPS location and IMU data from consumer drones, aerial data derived from the photogrammetric process is not accurate enough. An uncorrected GPS is only accurate down to a meter, the IMU needs to be perfectly aligned with the camera, and for a drone traveling at 15m/s even a 500ms time delay from when the camera is triggered and the image is recorded means it has already traveled 7.5m. The implication for the accuracy of orthographic surveys is sever. 

If you were doing three or four of these jobs a week then exploring alternatives is probably something you should consider.

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This is the type of work we are beginning to get and are aiming to get more of. However we imagine most would not require the entire roof such as this. We normally fly manually which is obviously much more skillful - in many cases we will have to fly manually anyway as we wouldn't fly auto in more built up areas. 

Completely get GPS accuracy etc. Yes we could upgrade; something we would consider in the future but I don't think we would be auto mapping that many entire roofs for it to be a sole decision. I know people who do similar work and they seem to do it mainly manually with such tasks, however we're not a team to shy away from trying different things.. especially if it will save us hours of work & batteries! The automation side is just something we wanted to test as you can appreciate at such a low altitude, needing so much detail it can be around 500-600 images for a 10,000 sq ft roof. 

This is the only 'mapping' as such we would normally need to do - we don't actively seek work in this area.

Cheers for the help - at least I have something to go out and test... if not, just stick with manual. 

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With drone deploy the drone takes a picture while the drone moves along - hence the lack of clarity due to a low shutter speed as well as lack of accuracy on the location due to time it takes to take and store a pic. One solution would be to move the drone to a spot, stop and ensure the drone is still, take a pic, then move to the next spot, stop, take a pic - repeat through the 600 pics needed for the survey. There is a hard limit of 99 waypoints with DJI missions. However 6 - 7 missions could be created and then uploaded as needed to complete the survey.

Of course this method will take more batteries - that would be expected. However 10,000 sq feet is only a quarter acre which is not too large. 

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Yes we are going to be testing GS Pro now instead of DD - that seems more suited to our requirements!

We can test both the map/ start stop options to see what works best. I'm confident it will still work moving (just with a higher shutter) or if not we can go for the start stop method. If either work its still better than having to complete manually. 

As mentioned above - I didn't know the height impacts the shutter so much! 

What is your experience using GS Pro?

 

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I haven't used GS Pro so I've no advice there. I thought GS Pro is only iOS and I use android. 

On a slightly different note: I'm thinking there needs to be a skills test for folks that want to do inspections. The test would be to fly long inspections manually, over a building with no visual cues, keeping a heading, snapping a pic every 10 feet, avoiding objects, and completing a lawnmower pattern.

It is surprising difficult to complete what seems like a basic task.

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Yes it's currently just IOS. 

And that's exactly what we do for inspections currently.  Forward taking images... Backwards taking images. Addional shots for even further detail on gutterings, fixings etc. It's very difficult and takes a long time. And when with a 45mm lens? Twice as hard... Very close up shots, lack of positional awareness meaning even more difficulty.

The most difficult is checking through the imagery afterwards to ensure you haven't missed any spots...

Edited by Jacko92

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Let me offer a different perspective as I am co-owner of a large commercial roofing contracting firm in the Mid-west as well as operating a UAS commercial service provider specializing in building and structure and inspections.  I have personally performed hundreds of such roof inspections over the past two years.  

My suggestion to you is you are overthinking all of this.  There is little need to be zooming in and out with your lenses on these flights.  I have  both a Inspire 2 with a X4S lens and an Inspire 1 with a standard issue lens as well as a Zenmuse Z3 with zoom and a Zenmuse XT FLIR scanner.   I use the zoom only when there is a defect area I need close up images on.  The resolution on all these cameras are outstanding (up to 20 MP) and if you just do a good flyover and watch your exposures etc the images you take are very detailed.  You can quickly blow them up on the computer screen and the resolution allows the detail of the roof surface to hold up.  I even use a Phantom 4 Pro and at times rather than set up a ladder to check out a project I just send up the P4P and take a bunch of pics then check it out back at the office and share with others for their opinion and discussion.  Also Drone Deploy is great but I almost always shoot manual and the roof sizes are as big as 300,000 - 500,000 sq. ft.  It's more important and I strongly believe you get better results by flying your drone manually to get as close as you can and let the wonderful cameras on these units do the work.  

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Appreciate your perspective on this and thanks but our clients request as close as possible! When I say zooming I'm talking about the quality not the fact that zooming will be necessary. If we do our job probably there shouldn't be a need to zoom... But at least the option is there. 45mm is the best lens on the X5 for this task! 

Would love to know how you do 300,000Sq ft manually!  That must be a HUGE amount of batteries and easily 2,000+ images????

I'm not sure I agree that the same result cannot be achieved automated if planned correctly. 

Edited by Jacko92

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Hi Jacko92,

To solve your issues regardless of platform or who processes you would best to:

  1.  Increase your shutter to at least 1/1000...this will eliminate your blur
  2. Work out what your complete cycle time is on the camera fitted. This affects your flight speed and how quickly you move between photo stations. as an example one high end mirror-less camera we use have a complete cycle time including write to card of just under 2 sec. We therefore make sure our flight speed between photo stations is around 2.5 secs. This way you never loose an image or get one that is out of focus. This is particularly important if the automated flight controller/flight plan is going to fly straight through and not stop/slow down at the photo station.
  3. A overlap of 70-80 for both frontal/side is more than sufficient to enable even the most basic photogrammetry product to process either an ortho or pointcloud. Remember even if your main deliverable is an ortho photo and you are using photogrammetry software it will still need to complete the "point cloud reconstruction" so that the software can complete the ortho-rectification process.
  4. Unless your are after correct spatial accuracy don't worry about the GPS, its just being used so the software can work out how many of the photos its needs to realistic compare to pixel match. You can after all with desktop photogrammetry programs process without GPS coordinates and the relative accuracy of the reconstruction is the same.
  5. Ensure that at the boundaries of the mapping area you either fly past the object of interest by 2-3 flight rows. Or we just plan a flight loop around the perimeter of the whole flight plan both clockwise and counter clockwise. Both these techniques ensure that you have at least 3 images covering the end of your target of interest. This way your edges can be reconstructed well.

Remember that no matter how good the processing platform says they are they can't break the rules or scientific principles used for photogrammetry, particularly SFM.

We complete all sorts of aerial mapping and close in inspection missions using a variety of cameras from the most basic cameras fitted to consumer drones like DJI, 42mp high end prosumer cameras and dedicated 100mp aerial cameras to achieve mission deliverables of GSDs of any where from 4cm down to 0.09cm. The above basic pointers enables all our missions to be successful.

Happy mapping and flying,

Dutchy

Edited by Dutchy

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Not sure if anybody already mentioned this but with a 45mm even set to infinity you will have a shallow depth of field. Since there are slight variations in both the roof elevations and probably a slight bit of up and down movement of the quad during the flight. Your depth of field may be shallower than the object you are trying to capture. That being said if you use a lower mm lens like the 15mm that comes with the x5 you may find that more if your image is in focus. I routinely use the Olympus 14-42mm zoom during roof inspections. On the 42mm end of the zoom the depth of field gets very shallow to the point that the object in the foreground may be in focus but an object just a few inches behind it will be out of focus.  Also if your 45mm is not an ASPH lens you will get pincushion distortion in your images making them not line up completely when they are spliced together in the app. I would try it with the 15mm and see if you get better results. I hope this is helpful.

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