Topics

1

Feature Requests / Ground control and markers

« on: March 25, 2012, 01:00:21 AM »

Hi,

In our last projects, using v0.8.4 we did some experimenting with the ground control settings. While certainly already functional, I think there are some improvements that can make this feature much more useful. Here are some comments and recommendations.

- placing GCP's (markers) in itself works well, zooming in and out is fast and it helps a lot that markers can be seen on the model as well as on the photo's
- as I understand now, when adding a marker before the model geometry is constructed, this markeris only on one photo. When adding it after model construction, it is also added on every photo where it is visible. This is a nice feature, but it can cause a lot of work to place every point right. e.g. in our last UAV project, overlap was between 65 and 85% so every marker was on between 10 and 15 photo's. We typically have between 10 and 20 markers per flight... My suggestion is to slightly modify the behavior as follows: when one adds a marker on a photo, it is automatically added on every other photo, but as a 'preliminary' or 'temporary' point, e.g. with a grey flag instead of a blue flag. When one opens a photo with a temporary point and moves the point, it becomes a 'definitive' point. Photoscan would then only use the 'definitive' markers for calculations, while the temporary points are used to assist the user.
- the use of markers as tie points to optimize the point cloud/camera calibration seems a very strong feature to me. Calibration parameters supplied by UAV manufacturers may not be that reliable and/or not entirely compatible with Photoscan. As I understand this feature now, there may however be an issue with the processing chain: 1. align photos, 2. build geometry as it is much easier to place markers, 3. optimize point cloud which detroys the model (am I right?).
To avoid building the model twice, it could help if PhotoScan could place preliminary markers on photo's directly after camera alignment. If a user enters or imports reference X,Y and Z coordinates, an initial estimate of the position on the photo could be made assuming a flat terrain. Now users can position the markers right (not necessarily all of them), optimize the point cloud and then build the geometry.

Best regards,

Jan

2

Camera Calibration / skew coefficient

« on: September 25, 2011, 08:09:20 PM »

Hi,

In the Agisoft Lens manual and website, there is a good description of all the parameters except for the skew that is not mentioned but is part of the xml. Is this parameter actually used and if so, is it possible to update/post the equations (see appendix in the manual)?

Many thanks,

Jan

3

Bug Reports / export orthophoto, bounding box and pixel size

« on: August 27, 2011, 11:45:53 PM »

Dear forum,

Export orthophoto seems to have some issues resulting in slightly smaller pixel sizes than entered in the textbox.

e.g. when I enter 1 m as pixel size and take care the bounding box min/max limits are also rounded to 1 meter, the resulting pixel size is 0.999899 m. Bounding box margins are also slightly off.

When instead I use the max. image size textbox instead of pixel size textbox, I can avoid the issue. e.g. I want a 1 m pixel size and have an area from 536200 to 537200 (1000m) in X and 25600 to 26000 in Y (400 m), I enter 1000 m as max image size and the resulting image has exactly 1 m pixel size. In this case however, the resulting image goes from 25600 to 25999 in Y (399 instead of 400 pixels).

Note: in my case, both the model and the export coordinates were in UTM 31 N.

Best regards,

Jan

4

Bug Reports / model export to obj, coordinates truncated

« on: August 14, 2011, 11:29:21 PM »

Hi,

When I export my model in UTM coordinates to .obj, all X and Y coordinates (not Z) are truncated to integer values (rounded off at the meter). This does not occur when exporting to .ply (so I have a work around using Meshlab). It also doesn't occur when exporting the points to .obj.

Best regards,

Jan

5

General / Matching a large number of photos in PScan pro

« on: July 29, 2011, 05:16:10 PM »

Hi,

We are trying to match 14 UAV flights, totalling 8000+ photos into a limited number of chunks. The photos have a decreased resolution so that we don't run out of RAM memory.

The processing time of the first steps in the photo matching process seems to linearly increase with the number of photo's. The last step, "estimating scene structure" however seems to exponentially increase with the number of photos. We first tried with all 8000 photos but progress got stuck at 0%. A chunk of 2800 photo's is currently running and may eventually finish after 20 hours or so. Chunks of 600-800 work in less than one hour.

Does anyone have an experience with the maximum feasible limit of number of photos?

Note: RAM memory did not seem to be an issue in this step, we didn't get above 85% commit.

Many thanks,

Jan