Messages

406

General / Re: Importing georeferenced .obj model to Meshlab

« on: March 17, 2014, 10:22:48 PM »

Yep he looks dead, nice model!

Could you tell me what's keeping you from using local coordinates, as this model appears to be quite small so I personally see little use for a coordinate system.

407

General / Re: GCP error low - high errors on DEM

« on: March 17, 2014, 08:02:52 PM »

I've checked the GCP heights on the DEM that I made. Even though I told Photoscan that the marker accuracy is 0 the height at those exact GCP locations is way off.
Photoscan was talking about an error of 3.6 centimeter however the GCP's that should match 1:1 in height do not match at all, and in some cases the error is up to 40cm!

How is this explained? Photoscan says the error is low, I've told it that the marker accuracy is 0 and thus absolute but it doesn't use those absolute heights for DEM creation.

408

General / Re: GCP error low - high errors on DEM

« on: March 17, 2014, 03:20:54 PM »

Do you think it's worth starting over from scratch in case something went wrong?

I've unchecked a few GCP's and reoptimized again. Some of the unchecked GCP's stay on the same error(m) except a single pair that went haywire and suddenly gave an error of over half a meter even though the position in the photo hasn't changed. Corrupt project perhaps?


On a second optimization things went completely Fubar.. Unchecked three more GCP's only to see that their respective errors went from a few cm's to nearly a meter, 30cm and 25cm...I've decided to start all over again.

I assume using a camera accuracy of 10m is the best setting for aligning the photo's by just the camera GPS position?

409

General / Re: GCP error low - high errors on DEM

« on: March 17, 2014, 02:34:39 PM »

Hi Alexey,

Yes I've optimized the alignment, first by just the GPS camera position (from a Cessna 172) and then after I accurately placed all 67GCP's I've reoptimized it again with all the camera positions unchecked and just the GCP's. In the ground control settings I've set the marker accuracy at 0 since they're measured with RTK GPS.
Photoscan gives an error of 0.036m and 0.768 pixel error, does this sound correct to you?

PS, I'm on the latest version and build.

410

General / GCP error low - high errors on DEM

« on: March 17, 2014, 01:48:04 PM »

Hi,

I've finalized generating a 400 hectare land DEM using 67 GCP, all measured with RTK GPS.
Photoscan says the GCP error is 0.036m however when I evaluate the DEM with RTK GPS checkpoints made in the field, far larger errors are found in excess of over 20cm in the Z value.

Is there any explanation as to why? Even exact locations of GCP in the DEM give out false readings when compared to the absolute values of the GPS measurement even though those points should match 1:1?