Some questions from a newbie

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JasonBSteele
Posts: 6
Joined: Sun Apr 28, 2019 6:31 pm

Some questions from a newbie

Post by JasonBSteele » Sun Apr 28, 2019 7:40 pm

Hi,

I've been taking a look at DH Basic today. I haven't even had a chance to use it with my Mavic Air yet but I do have a few questions.

I'm interested in doing a photogrammetry project the site is only 6m x 6m x 10m tall.

I drew the building and the surrounding obstacle trees and chose the Inspection->Site plan. It created 4 separate plans of 12, 30, 34, 34 images which seems a lot but then I guess this is driven by the overlaps selected when choosing the plan.

The first plan (of the roof) has an option to Simplify which reduces the number of images, but the other plans do not.
1. Presumably I cannot change my overlap parameters after generating the plans?
2. Why does the first plan have a simplify option but the others do not?
3. Why are 4 separate plans generated rather than a single one - surely it's not expecting to get through 4 batteries?
4. Can plans be joined to each other?

I saved my plans and then thought I would start a new one elsewhere, but it started adding more plans to the existing 4 rather than starting again with none.
5. How do I start a new plan?

My second site has an OSM plan so I accepted that, however the outline of this is way off what is shown on the map, as shown in the screen shot:
https://drive.google.com/open?id=18nPTv ... We-SGCh02j

6. This is concerning, which is "correct", the sat image or the outline?
7. Is there a way to calibrate the actual GPS reading when on site against the plan?

I then started to look at creating a complex manual plan for another plan (video rather than photogrammetry this time) and quickly started to find it a very fiddly process on my admittedly aged Nexus 7.
8. Are there plans to support creating plans using a Windows or Web UI? If so is there a rough ETA? (I want to know whether to be patient and wait a couple of months, or grit my teeth and wrestle with the Nexus 7).

Many thanks,
Jason

gil_dh
Posts: 11
Joined: Tue Apr 10, 2018 3:26 pm

Re: Some questions from a newbie

Post by gil_dh » Tue Apr 30, 2019 12:16 pm

Hi Jason,

To your questions:

>> I drew the building and the surrounding obstacle trees and chose the Inspection->Site plan. It created 4 separate plans of 12, 30, 34, 34 images which seems a lot but then I guess this is driven by the overlaps selected when choosing the plan.

Indeed. The number of waypoints is chosen based on the overlaps (vertical and horizontal) that you select, the resolution you want to achieve (determines the distance from the object) and the camera profile.

The first plan (of the roof) has an option to Simplify which reduces the number of images, but the other plans do not.

Indeed. The simplify function works as follows: a waypoint A that is between two other waypoints B and C is only removed if its position is on the line segment between B and C AND the camera angles are an appropriate interpolation of the camera angles of the B and C. Intuitively this means that if you smoothly transition between B and C (both the position and camera angle), ignoring the existence of A, you will at some point in the transition be at the exact position of A and with the exact camera angle of A.

Mission simplification is useful for Top-Down type missions in which the user intends to use interval shooting mode, which means that camera triggering works by shooting a picture every x (user defined) seconds. If you want to guarantee exact overlaps and have better control of where pictures are taken it is a good idea to keep the other waypoint and use fly-by or stop and shoot.

>> 1. Presumably I cannot change my overlap parameters after generating the plans?

Correct. Once a mission is generated, it is possible to manually change its properties (e.g. by selecting waypoints and moving them etc.). To get a plan with the updated overlaps you should go through the mission planning wizard again and plan a new flight.

>> 2. Why does the first plan have a simplify option but the others do not?

Probably because the app identifies that there is no waypoint that can be simplified (with the role stated above). You can still remove waypoints manually by selecting them and deleting them (garbage can icon).

>> 3. Why are 4 separate plans generated rather than a single one - surely it's not expecting to get through 4 batteries?

No. It is intended to give you the freedom to choose which "levels" of the site scan to perform. Once one mission is finished, you can immediately start executing the next one, without even landing. If you choose to do so, make sure to inspect in the 3D view in the launch dialogue the exact trajectory that the drone will take from its' current position to the first waypoint of the next plan you are launching.

In general, you can fly as many missions as you want with one battery.

>> 4. Can plans be joined to each other?

Not at the moment, but this is a feature we are working on. Perhaps you can make use of features in Drone Harmony Plus like Perimeter Verticals or Perimeter Horizontals (see out user guide for details) to achieve the type of mission you imagine.

>> I saved my plans and then thought I would start a new one elsewhere, but it started adding more plans to the existing 4 rather than starting again with none.
>> 5. How do I start a new plan?

The app works with the concept of states. A state can include multiple missions. If you would like to only see the mission you are currently working on, you could save the state, delete the missions from the scene and start planning new mission. Be sure to not overwrite the previous state when you save the next time.

We are working on better grouping options to make it easier to navigate through the generated missions in the right menu.


>> My second site has an OSM plan so I accepted that, however the outline of this is way off what is shown on the map, as shown in the screen shot:
https://drive.google.com/open?id=18nPTv ... We-SGCh02j
>> 6. This is concerning, which is "correct", the sat image or the outline?

From our experience, there can be significant deviations in the map imagery. We usually trust OSM more than the outline that "makes sense" from looking at the image. It is, however, not a rule, and when in doubt it is good to use the drone's GPS to inspect the actual position of some key point in the scene (for example, by placing the drone at a corner of the building and inspecting in the map view where this point is).

>> 7. Is there a way to calibrate the actual GPS reading when on site against the plan?

Yes (and this is also another option to solve issue 6. above) Use the "Calibrate Position" option in the "Manual" tab in the plan catalog. This options lets you manually fly a very short flight above a key corner point in the scene and approve the calibration run once straight above it. The entire scene with the missions will then be translated to the real position of the objects in space with respect to the drone's GPS. This approach also has the advantage of accounting for internal GPS shift in the drone. It might, however be an overkill if you are not flying very close to the structure.


>> I then started to look at creating a complex manual plan for another plan (video rather than photogrammetry this time) and quickly started to find it a very fiddly process on my admittedly aged Nexus 7.
>> 8. Are there plans to support creating plans using a Windows or Web UI? If so is there a rough ETA? (I want to know whether to be patient and wait a couple of months, or grit my teeth and wrestle with the Nexus 7).


You have excellent timing for this question. Please follow the Drone Harmony news in the next days ;)

Let us know if we can do anything else for you.

Best wishes

DH Team

JasonBSteele
Posts: 6
Joined: Sun Apr 28, 2019 6:31 pm

Re: Some questions from a newbie

Post by JasonBSteele » Tue Apr 30, 2019 12:42 pm

Thanks for taking the time with this great response!
>> 3. Why are 4 separate plans generated rather than a single one - surely it's not expecting to get through 4 batteries?

No. It is intended to give you the freedom to choose which "levels" of the site scan to perform. Once one mission is finished, you can immediately start executing the next one, without even landing. If you choose to do so, make sure to inspect in the 3D view in the launch dialogue the exact trajectory that the drone will take from its' current position to the first waypoint of the next plan you are launching.
Yes, it would be great to be able to join these together into one flight plan as having to fly 4 separate flights for a small 6mx 6m x 10m building does seem a little excessive.
>> 5. How do I start a new plan?

The app works with the concept of states. A state can include multiple missions. If you would like to only see the mission you are currently working on, you could save the state, delete the missions from the scene and start planning new mission. Be sure to not overwrite the previous state when you save the next time.

We are working on better grouping options to make it easier to navigate through the generated missions in the right menu.
Okay, good to hear that there are changes coming to deal with this. I found this to be the most confusing aspect of what was otherwise a very intuitive app.

Regarding the calibration: thanks for the suggestion to use the Calibrate Position plan. I will definitely take a look at this as the discrepancy between the sat image and OSM plan is actually many metres and would have put the UAV inside the building!

And finally... looking forward to the announcement in a few days! ;)

Many thanks

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