Topics

1

General / Filter Photos by Markers

« on: January 08, 2017, 02:23:27 AM »

My workflow previously has been upon aligning photos and creating a sparse point cloud, I would thereafter identify each GCP on one image. Then I would right click on the marker and selected "Filter Photos by Markers". Thereafter it was very quick to simply go through the photos in the photo window and fine tune the positioning of the marker on all the photos.

However, now when I select Filter Photos by Markers, it only shows me the one image that I have specifically identified as the GCP. In addition, there are a number of red and white dashed lines crossing through each defined GCP.

I am wondering if I have mistakenly changed a setting somewhere but can't seem to locate anything here.

Anyone have similar issues or any suggestions on how to resolve?

Thanks in advance.

2

General / Data management and file delivery - large files

« on: April 19, 2016, 06:33:19 AM »

Hello. I surveyed a gravel pit approximately 40 acres in size. The final project worked out very well. Now I would like to send the data to my contact at the gravel pit so that he can import it into Auto CAD. He would also like the orthophoto file.

I have created a DEM and exported a DEM as well as orthophoto. However, the resulting file sizes are over 100 MB not so easily sent electronically.

I am relatively new to photogrammetry and PS and as such, the questions may seem quite elementary but I appreciate any help anyone may be able to provide.

1) What file types generated from PS do you find work well for users of Auto CAD and in general, any settings that should be applied in the generation or exportation steps to ensure that accuracy is retained?

2) Are there any tips and tricks to generating high quality DEM and orthophoto files that retain a reasonable level of accuracy and detail but are much smaller in size?

Thanks in advance.

3

General / Decimation and "fixed length per point"

« on: January 29, 2016, 03:20:35 AM »

If I understand correctly, there is an algorithm in place whereby Agisoft upon decimating the project will look at neighboring vertices to determine how many points should be retained - ie - more points in areas where large changes on the axis. For the purposes of aerial surveying, this would generally be with respect to large changes in elevation.

I have a contact who has requested a point cloud with one point per 20 cm (whether he is implying squared or cubed I am unsure - lets assume it is cubed). This is generally how he determines the level of accuracy that he would like to have for the given area.

In Agisoft I dictate the number of faces to retain when decimating the mesh, however, this is difficult to convert into a measured distance between pixels that may be requested. Is there some other way to communicate the level of accuracy of the point cloud? The number of faces will provide very different accuracy dependent upon the area included.

I do believe that the algorithm that Agisoft uses would produce a much better result with an average of every 20cm than a point every fixed 20cm. I am not arguing the method - just the communication of the results.

Any ideas or tips here would be appreciated.

Thanks.

4

General / Filling in gap from aerial survey

« on: January 21, 2016, 02:00:32 AM »

During an aerial survey the camera slipped on the gimbal and instead of shooting straight down, the shot was slightly to the right. As a result, when doing the UAV survey, there is a small gap in the model due to no photography captured of the area.

The gap is relatively small and it would be ok to assume that it will follow the contours beside it.

I can't seem to figure out how to do this effectively. I have tried to select the "gap" and the points in the dense cloud adjacent to the gap and then select Close Holes from the mesh tool but this closes holes all over the place.

Anyone know how to do this. Also - if there are some good videos or manuals demonstrating instances like this in english I would greatly appreciate someone pointing me the right way so I don't have to bother everyone on here so much.

Thanks for your help.

5

General / Volumetric Calculations and Saving Data

« on: January 19, 2016, 02:53:03 AM »

Case - surveying gravel pits. The crusher gets paid $/cubic meter.  We survey with a UAV with GCP's and utilize Agisoft solution to calculate volumes.

In one survey/stitched total there will be multiple stockpiles.

We do the volumetric calculations within Agisoft. However, the volume can vary from time to time based upon where the outline of the stockpile is determined when defining the pile. As such, we would like to have a file that records the results of each volumetric calculation as documentation of the measurement.

Is there a way to do this easily so that if there are any questions regarding how the amounts were measured it can be shown and demonstrated easily? And can be provided to the customer in an easy to read format?

6

General / Mixing reference systems between camera and GPS

« on: January 19, 2016, 02:44:53 AM »

Surveying with UAV. Camera utilizes WGS84 system coordinates. The GPS coordinates utilized in camera allow more efficient initial alignment.

GCP's then may be on a local coordinate system. If this is the case, is there a problem?

I have a project whereby the photos were input, alignment done initially, GCP's registered and thereafter uploaded the local coordinate GPS points of the GCPs. Result is a mess. Not sure why.

Any experience with similar issues?

Thanks in advance.

7

General / Aerial imagery without GPS = upside down model

« on: January 06, 2016, 06:37:30 PM »

We flew a site with the UAV to obtain aerial imagery. Unfortunately the GPS tagging did not work on all photos. We do have GCPs.

We tried to align photos with GPS tagging on some photos but not on others. The result was a model that looked blurred or "doubled".

Thereafter, decided to remove the GPS tags from all photos prior to importing into Agisoft. Align photos with generic and thereafter add GCPs and correct alignment.

However, after the generic alignment, the model appears upside down. When I press shortcut 7 to see from above, the points are actually on top of the camera markers.

We are hoping to generate a 3D model to compare to the prior survey to see how much the landfill has filled since the previous survey.

Questions:
1) What causes the model to be "upside down"?
2) Will this have a significant impact on the accuracy of the final model?

Thanks for your help.