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Messages - stihl

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61
General / Re: "Warped" vegetation in Orthomosaic
« on: September 04, 2017, 01:06:43 PM »
Keep in mind that the resolution you build the ortho from will factor into things. If your client only wants an ortho with a GSD of 1/2 ft (0.15m) pixels, building it at scale will automatically smooth out some of the inconsistencies as there is less precise image matching needed than if it were a full resolution (more like 1cm pixels) render.

I too use this technique. If my client specifically needs a True Orthomosaic, I'll offer it at 5 cm and collect the data at 1.5 cm GSD. This will ensure an aesthetically pleasing True Ortho.

62
General / Re: CUDA Error 999 at line 112
« on: August 23, 2017, 05:35:05 PM »
I too have tried Pix4D. I sometimes use it to cross check the quality of the dataset and although it is faster in some parts of the process it's definitely more cumbersome or slower than Photoscan in other situations. It entirely depends on what you need to get done.

For instance, creating artefact-free Orthomosaics in Pix4D of datasets larger than 100-200 images is extremely slow and cumbersome. And it's practically impossible when the dataset is any larger than that. Photoscan does not have such issues.
Photoscan also offers much more flexibility when it comes to minumum amount of overlap or the use of different cameras in the same chunk.

By the way, go and ask Pix4D and they'll acknowledge this: your 2 Pix4D usable licenses are not meant to be used on 2 workstation computers. It's meant to be used on 1 workstation and 1 laptop in the field. Using a single license on two workstations is not what Pix4D is offering and they will not condone it.

What you should have done is create several project versions. Version 1 for the inital alignment, Version 2 for the referenced chunk and a Version 3 before you start building your products. That way you can always go back to V2 and use that one on a different computer when issues arise. This comes down to proper planning.


63
General / Re: Making Sense of Errors.
« on: August 22, 2017, 10:54:53 AM »
That is correct. The error shown is a shift that Photoscan had to implement in order to achieve a good set of tie-points according to the results of the image matching. These should then be further refined by the use of survey grade ground control points.

The GPS of your DJI  drone should not be considered as accurate. Furthermore, the altitude is usually wrong because its zero value is usually the place where it took off. I.E. it's a 'height above ground level' (AGL) value and not one that's referenced to the WGS84 ellipsoid which is the case for the X and Y coordinates.

Information about this subject can be learned by taking photogrammetry and or surveying courses or studies.

64
General / Re: Orthomosaic Artefacts How-Too
« on: August 07, 2017, 11:40:07 AM »
The artefacts are due to incomplete geometry on the edges of your building rooves. Because the default build Orthomosaic relies on using the all of the points of the dense point clouds, any missing geometry there will result in artefacts in the Ortho.

To overcome this you will need to rebuild a new DEM that's only using the Ground points. The first step is to run the automatic ground classification tool and then only choose Ground in the Build DEM window.

Then rebuild your Orthomosaic based on the DEM (instead of the Mesh). When it's finished go to the Orthomosaic Viewer and you will notice that the artefacts are gone but now you will have to deal with building lean. You will have to manually edit the Orthomosaic by placing polygons around objects (such as buildings) and manually choosing an aesthetically pleasing photo by right clicking the polygon and choosing Assign images.

When you're finished, use the button on the toolbar to Update the Orthomosaic and export it as a new TIFF file.

65
General / Re: Showing a model, how to export
« on: August 03, 2017, 12:37:59 PM »
I'd advice to export it to Sketchfab for online model viewing. There's an automated method to upload it directly  from Photoscan to Sketchfab in the File > Upload Model menu.

66
General / Re: Please Help. Selecting lens and Shot arraignment
« on: July 23, 2017, 03:54:32 PM »
Photoscan has absolutely no problems aligning wide angle lenses.
I've processed thermal images in the past that were shot with a 5.5mm lens.

With sufficient overlap and good quality photos (well lit, no motion blur) Photoscan is able to calibrate the camera automatically during the alignment step.

Therefor before the alignment it is important that all the values in the camera calibration are set to 0, except for;

-Pixel size: this value is the physical size of one pixel on the sensors of your camera. The term is called the pixel size or pixel pitch. This value is a static value that has to do with the camera being used. This value can be looked up or calculated by following these steps.

-Focal Length: for your configuration this has to be set to a value of 24, which you did.

-f value: this value will be determined by Photoscan after correctly filling in the two values above.

Set type to Auto which enables Photoscan to change the camera calibration values.

Once your project is aligned using the correct pixel size and focal length you will notice that Photoscan has calculated all or most all of the calibration parameters. These new values can be found under the Adjusted tab in the camera calibration window.

67
General / Re: Interpolation DEM
« on: June 28, 2017, 09:16:42 PM »
Build DEM creates a DEM using IDW interpolation, Build Mesh creates a model using TIN.

68
General / Re: Change Detection using Photoscan?
« on: June 19, 2017, 04:02:02 PM »
The comparison was most likely done in software like CloudCompare.
You are correct that Photoscan does not have this option.

69
General / Re: Skatchfab model pixelated
« on: June 02, 2017, 11:13:06 PM »
It entirely depends on the texture settings you've used to generate your textured mesh model.

What's the texture resolution? The default value is 4096 x1. But as far as I know Sketchfab only allows up to 8192 texture resolutions which isn't very high. Perhaps there are ways to overcome this issue.

70
General / Re: Help with Chunk Alignment
« on: May 29, 2017, 05:32:32 PM »
The manual found here for the Pro version has a lot to say about markers: http://www.agisoft.com/pdf/photoscan-pro_1_3_en.pdf

Are you using Photoscan Pro? It's needed to use markers.

71
General / Re: Importing a .xyz pointcloud back into PS
« on: May 29, 2017, 12:51:51 PM »
Hi Riko,

Simply open your first project and then go to File -> Append and select your second project.
Repeat this process until all the projects are imported into one project and in individual chunks.

Then merge the chunks. Either with corresponding markers or use the image based alignment to merge the chunks together, one at a time.

72
General / Re: resolutions of Orthomosaic
« on: May 29, 2017, 12:48:52 PM »
The default value is the average photo resolution found across all the images. This corresponds directly with the project GSD value.

Upsampling (entering a lower value) will result in a higher resolution photo but the pixels that it's lacking are being interpolated by the neighboring pixels. So in essence the Ortho will have a higher resolution but the level of detail will remain in the same. So there isn't really any point unless you need an Ortho on a specific resolution.

73
The result you want to achieve is to maintain a relatively constant point density throughout your project location.
The way to do that is to make sure you have sufficient overlap whilest the UAV is flying over mountainous terrain.

As the height AGL gets decreased because of the terrain raising in elevation this will result in a decrease in overlap if this is not taken into account with the flightplan. This will result that the top of the mountains will have a lower amount of overlap than the rest of the area which can result in not being able to properly reconstructed the topside of the mountains.

74
General / Re: Problem with overlapping images !
« on: May 16, 2017, 04:26:55 PM »
Hi Ramadnio,

What you'd like to do is create a Mesh based on the *ground* points of the Dense cloud.

This will ensure that you can create an artifact free Orthomosaic.

After generating the Dense Point Cloud, run the automated classify ground points alghoritm with the default parameters.

Then generate a new Mesh with only these ground points. This can be done in the Build Mesh window.

Once that's done simply doubleclick on the Orthomosaic in the workspace pane and create polygons around objects and buildings to manually select an appropriate image for that particular polygon.

75
General / Re: DSM Generation
« on: May 10, 2017, 01:09:52 AM »
DSM = DEM = height model of everything

DTM = height model of merely the terrain

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