Messages

31

General / Re: Difference between volume and area from DEM and MEsh

« on: May 30, 2019, 09:46:11 PM »

Hello wizprod,

Yes, mesh based calculations are providing the area value as a sum of areas for each polygon of the model. DEM-based area measurement gives you 2D area estimation.

Thanks! So the trick to only have it show the correct surface area is to not close the holes, and hence not closing the "ground"?

the based plane cannot be confirmed, like it can be done for DEM based measurements.

So for the volume, the correct/most trustworthy way to do it is through the DEM ?


Is there a way I can re-use the polygon shape from the DEM on the Mesh, so the outlines are exactly the same ?
I use the surface-area for error-estimation calculations.

32

General / Difference between volume and area from DEM and MEsh

« on: May 30, 2019, 07:04:59 PM »

Hi!

I have an issue where a stockpile will have different volumes and areas depending on its processing-origin.

From Mesh:
- Area: 5158 m2
- Volume: 7139.9 m3

From DEM:
- Area: 2307.9 m2
- Volume: 7271.9

I suspect that the area reported by the Mesh is a total surface area, also on the buttom side ?
But given that the outline is more or less the same, why is there a 132 m3 difference between the 2 methods ?

33

General / Re: Auto detect not recognising coded targets

« on: May 30, 2019, 05:37:47 PM »

The surrounding area is quite sensitive, and needs to be somewhat larger than the outer black circle. Is also seems that detection is done in a rectangle. so have that in mind when designing the targets.

Also take care that no shadows are cast onto the targets.

I have attached one of my targets. Plate is 60x40 cm, "active" area for the target is 40x40 cm, and outer black circle is around 30 cm in diameter.

34

General / Re: Aerial Mapping - CPL Filter

« on: March 16, 2019, 11:24:21 PM »

It will depend a lot on the subjects that are reflecting. In many cases, you might not have an effect at all.
Optically, I don't think you'll have an issue what so ever, as long as the filter remains on and at the same position throughout the flight.

35

General / Re: Dense Cloud Quality

« on: February 28, 2019, 11:21:17 AM »

On High, the images are used at original size. On Ultra, they are interpolated to 2x size.

36

General / Re: Normal Spec 2 computers VS High Spec 1 computers

« on: February 26, 2019, 10:34:15 AM »

In the configurations you present, then the 1 computer-option will be better.

37

General / Re: Volume measurement accuracy

« on: February 26, 2019, 10:27:11 AM »

Hi, I met the similar problem like you. The volume measured by Agisoft is two-fold over the real volume. Did you find a way to optimize? Thanks.

If you are 2 fold over, I think you have other issues than just poor alignment. The coordinate system must be wrong?

38

General / Re: Volume not measured in Ortho view

« on: February 21, 2019, 06:21:30 PM »

Hi,

I want so use Agisoft for Volume measurement. I use the Ortho view but after drawing a polyline in the measure shape 'Volume' is not enabled. I don't understand why the volume can't be calculated.

Thanks
Lena

You have to create the DEM for the volume measurement to work.

39

General / Re: Calculating volume error from GSD or GCP ?

« on: February 21, 2019, 06:19:35 PM »

Trying one more bump!

40

General / Re: image alignment of forested areas

« on: November 27, 2018, 12:19:52 PM »

You probably won't have enough overlap with those high trees. Try and increase the overlap. Dronedeploy has some good tools for calculating this.

41

General / Re: GCP Error Explanation

« on: November 23, 2018, 08:39:22 AM »

If the base station has 2 m accuracy than you can not expect the GCP error to be low I do RTK measurements with 2-5cm accuracy and my GCP errors are (after point cloud optimalization) abour 5cm.
Packy

The absolute coordinates of the base will not affect the relative accuracy of the rover. So you could have a base offset by many meters, and still have a relative accaracy of a very few millimeters. They are as such unrelated.

42

General / Re: GCP Error Explanation

« on: November 23, 2018, 08:37:02 AM »

They were collected with an Emlid Reach RTK GPS. However, I believe the way I set up my base station the global accuracy of the base position is only about 2 meters.

Best,
Chelsea

Hm, it should be down to 2-5 mm’s... I own a couple of Reach units (RS+) as well, and they are extremely precise.
Maybe your GCP’s were disturbed? Your rover pole not leveled completely?
Do you have some pictures of the environments your captured the points in?

43

General / Re: GCP Error Explanation

« on: November 18, 2018, 10:16:30 AM »

How were they collected?

44

General / Re: Calculating volume error from GSD or GCP ?

« on: November 15, 2018, 01:58:48 PM »

Bumping this one. Anyone?

45

General / Re: DEM from same raw DATA problem

« on: November 01, 2018, 10:17:32 AM »

I assume you use a drone for this?
Do you disable the location of the camera (GPS exif) from the calculation?