Messages

1

General / Re: Geometry Accuracy Calculations/Validation

« on: November 23, 2011, 01:34:11 PM »

I don't know if other people have requested this for future versions, but I think that including the RMSE values in both pixel and distance (m) would be beneficial for users. Maybe some kind of toggle option or setting where a user could change units px, m, ft, etc.

2

Feature Requests / Visual DTM Alignment for DEM Export

« on: November 23, 2011, 10:48:49 AM »

I have two models of the same area (riverbank) that were created at two different time periods. I want to try and measure the difference between these two models, however, my surveyed coordinates were a few feet off, which causes models to be really of when exporting them as DEMs. Would there be a way so that you could view two DTMs in the same visual space, move them both around, and export them as DEMs? There are enough similarities in the models that a visual overlap would be sufficient, but I cannot figure out a good way to do this.

Thanks,

Tyler

3

General / Re: Geometry Accuracy Calculations/Validation

« on: November 23, 2011, 10:44:55 AM »

Thanks for the clarification Alexey. I really appreciate it.

4

General / Re: Geometry Accuracy Calculations/Validation

« on: November 21, 2011, 02:03:05 PM »

Howdy again,

I am still looking for answers on these previous two posts...anyone know anything regarding these questions?

Also, regarding checking and unchecking GCPs in the GCP dialogue. What does unchecking a previously checked GCP actually do to an already created DTM? Usually I've been unchecking the GCP's that have really high RMSE values, which lowers the other RMSE values, but I would like a clear explanation as to what this actually does.

Thanks,

Tyler

5

General / Re: Geometry Accuracy Calculations/Validation

« on: November 19, 2011, 09:33:19 AM »

I just saw that in the GCP dialogue there is a TOTAL at the bottom that includes a Total RMSE. How is this value calculated? I exported all my RMSE values to Excel and did an average of RMSE values and although it was close, it was not the same as the TOTAL value.

Thanks,

Tyler

6

General / Geometry Accuracy Calculations/Validation

« on: November 19, 2011, 05:52:07 AM »

Howdy all,

Does anyone know if there is a "best" method for calculating or estimating the overall accuracy of a model that is generated? From all that I have read the only way to do that is with comparing actual elevation values that are surveyed independently or determined from a different method. Lets say I only have 15 GCPs that each have their own RSME value, is there anyway to estimate the accuracy across the model into a single value from the 15 RMSE values that I have? I haven't found anything in the literature and I just wanted to see if anyone knew.

Thanks,

Tyler

7

General / Re: Question about exported data (cameras)

« on: November 18, 2011, 09:45:48 AM »

Since I am just another user, my answer is probably not going to be the most trustworthy source. So I would wait for Alexey on the official status.

I personally have not exported any camera position data, other than just .txt files. In there you have: # PhotoID, X, Y, Z, Omega, Phi, Kappa, r11, r12, r13, r21, r22, r23, r31, r32, r33.

8

General / Importing Photos w/ masks and GCP's from another project file

« on: November 18, 2011, 04:48:34 AM »

Howdy,

I have two separate files that are of the same scene, but were created with two different cameras. Is there a way to import all of those picture files into the same chunk while keeping all of the GCP's and masks of the images? I couldn't figure out how to if there is and this would save a lot of time having to redo the GCPs manually.

Thanks,

Tyler

9

General / Re: Question about exported data (cameras)

« on: November 17, 2011, 05:22:31 AM »

When you say textured plane are you refering to the plane representing a camera position or a textured plane of the object you are making models of?

10

General / Re: DEM Exporting Validity

« on: November 16, 2011, 04:43:39 PM »

Thanks Alexey. That is really good to know for my particular application. I have a question regarding the angle at which one can export a DEM. I see that you can export it along all the different XYZ axes (with a bunch of different combinations). You can also export the current view and specify a marker. Would it be possible in the future to specify an angle between different axes? For instance, you could put in 45 degrees, and for this particular problem that I was having, that way the large boulder would not block the potential erosion behind it. That being said, there might be other parts of the image that would have two values, but I just think it could be something to think about for future versions.

Thanks again,

Tyler

11

General / Re: Accuracy of Point Cloud Changed?

« on: November 16, 2011, 03:55:53 PM »

Yes, that would make sense Alexey. I think I didn't explain myself correctly. What I am saying here is that I was doing the exact same "align photos" step for the exact same photos in the exact same project, but I ended up getting different results. I saved a project on two different hard drives, one of the files was on a network drive, and another was on a local drive and when I performed this analysis on each file, the accuracies were slightly different.

Could it be the way that the .jpg files are stored on an HD or something like that?

12

General / Re: Problems Building Geometry

« on: November 16, 2011, 02:58:43 PM »

I redid the right chunk in this project with more accurate GCPs, so it could have been that the GCPs were off, but the RMSEs were not that high. Here is what I am getting now though. You can see that there is primarily a single plane (which is a riverbank) and almost completely perpendicular there are at least two planar features that are just way off...Do you know how/why this happened?

Here is a screenshot:
http://www.tylerdepke.com/wp/wp-content/uploads/2011/11/Polygon-Build-Linear-Error.jpg

13

General / Accuracy of Point Cloud Changed?

« on: November 16, 2011, 02:42:19 PM »

I am running on a computer that has little local space on the hard drive so I've been going back and forth from a network drive to the local drive. I ran the same exact chunk in the same exact file with one file location on the local drive and another on the network drive because I just wanted to test performance for Aligning photos (I also ran a Build Geometry yesterday that took 20+ hrs on the network drive when it used to take about 12 on the local). The RMSE for my GCPs was significantly different between the two files...this seems super weird.

Screen shots of the two GCP windows are attached.

14

General / Re: crop of invalid DEM

« on: November 16, 2011, 02:25:07 PM »

I'm just posting this from The ArcGIS help, but I was struggling trying to figure out exactly how this works, but here is what I found.


Similarly, in Map Algebra, SetNull is used to change all values that meet a specified condition to NoData. SetNull can be used for processing the remaining selected cells, to eliminate certain cells for future consideration within a model, or to create a mask. The syntax is as follows:

outraster = setnull(inraster1 > 5, inraster1)

In the above expression, any cell with a value greater than 5 will be set to NoData, and the remaining cells will retain their original value. Any location on either input containing NoData will output NoData for the location.


So potentially you could just set that really negative value to be null within Arc, if that is what you are doing.

15

General / DEM Exporting Validity

« on: November 15, 2011, 01:51:56 AM »

Howdy again,

This question involves how that elevation value of a DEM is calculated if there are multiple polygons that exist for that particular projection. This could happen in real life if there was a cliff and an overhang. So, the DEM's that I am producing are not from aerial photos, but photos taken about 10m away from a stream bank where there is a nearly vertical outcrop of soil with a lot of boulders and cobbles at the bottom.

If there is a large rock in the foreground of the projection, will a DEM export the elevations of that rock, or the elvations of the bank behind the rock?

Here is some visual help. It is most helpful to look at the bottom right XYZ Axis to make sure you know what angle you are looking at, but the first picture is looking directly along the X axis so the Z-axis is completely Vertical, and the y-axis is completely to the right. In the second picture, the axes have been rotated so we can see behind this boulder, and that yellow "X" mark would not be visible if the DEM was produced looking along the X axis (like the first picture).


http://www.tylerdepke.com/wp/wp-content/uploads/2011/11/DEM-Q1.jpg


http://www.tylerdepke.com/wp/wp-content/uploads/2011/11/DEM-Q2.jpg

This would be very important for analyzing changes in volume of sediment and rocks from one time frame to another.

Thanks again,

Tyler