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Author Topic: Most effective way to create survey site plans using photogrammetry?  (Read 6743 times)

Shovelhead

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I currently work with a smaller surveying firm that mostly does legal work. As such, a large portion of what we do is topographic site plans as a first step for a client to get a demo permit, building permit, ECT ECT from the city. We display roads, utility's, buildings and other permanent features, contours and trees (including trunk diameter, drip line diameter), fences ECT.

I would like to use my phantom 4 pro to map out larger lots and multi-lot projects to save time and gather a more complete data set. I was thinking as for field work besides flying and capturing the images I would set up GCPs, find and tie property pins and a elevation monument and note the tree specifications. The rest I would hope to be able to take care of by digitizing the photos or point cloud but at that point I'm lost.

Is anyone else out there doing this? What is the best approach? Datumsurvey does exactly what I want by being able to digitize on oblique photos, which is handy obviously because if I were to digitize on an orthophoto I would miss a lot of features due to overhead obstructions (trees, eaves, ECT) the only issue is Datumsurvey's 15,000 price plus maintenance fees.

Any tips or advice would be very much appreciated.

Shovelhead

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No surveyors in here? I'm sure there must be more uses for photoscan for surveyors besides just volume measurements and bare land topos.

Jeremiah_ROWE

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I have some basic surveying experience and have been providing Agisoft developed point clouds to push into AutoCAD Civil3D. The ability to draw shapes and lines in PhotoScan is very useful. However, keep in mind that surfaces such as water and taller vegetation can prove to be problematic and give bad elevations.

If you keep in mind the restrictions and build that into your workflow you should find it very useful.

We have our field crews focus on getting shots in areas that we "cannot see" such as the bottoms of ditches or under canopy.

Shovelhead

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I have some basic surveying experience and have been providing Agisoft developed point clouds to push into AutoCAD Civil3D. The ability to draw shapes and lines in PhotoScan is very useful. However, keep in mind that surfaces such as water and taller vegetation can prove to be problematic and give bad elevations.

If you keep in mind the restrictions and build that into your workflow you should find it very useful.

We have our field crews focus on getting shots in areas that we "cannot see" such as the bottoms of ditches or under canopy.

So at what point does it make more sense to add photogrammetry to your workflow vs doing everything the conventional way (total station/rtk)

Thibaud Capra

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As a surveyor (hopefully in september I'll have my diploma!), I'd use photogrammetry to do surveys in very specific cases.
For facade surveys, a great way is obviously using orthophotos to have a quick plan of it.
As for sites, you already mentionned the masking issue and Jeremiah is right saying that vegetation and water may cause problems.

For facade surveys, I'd go for a mix of terrestrial and aerial photogrammetry, bearing in mind the rules.

TL;DR: Surveying site plans using photogrammetry is case dependant.
Best regards.
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Thibaud CAPRA
Master Student in Geodetic Engineering, Cartography & Surveying
Master Thesis in Automated Processing of UAV-based Photogrammetric Data (ResearchGate Link)
INSA de Strasbourg, FRANCE
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Shovelhead

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Back on the original topic, I found pix4d has a very handy tool to digitize on the point cloud called pix4dmapper. Does agisoft have anything that is comparable to that? Basically it allows you to draw a polyline on the point cloud and then fine tune it on the photos that contain it.

Darko

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Hi Shovelhead,

I am a professional surveyor doing my work for 33 years and for restitution of the drone surveyed models I am using Virtual Surveyor. Try it, it is free for the first month and later you can take the licence on monthly basis. The model it use is actually 2.5D, not real 3D and you are not able to see under the roof projection or under the three canopy.

But, as always, an idea came on my mind.
1. Make a nice HIGH quality dense point cloud
2. Classify Ground points from the cloud.
3. Make an arbitrary mesh out of the GROUND points only.
3. Make a DEM based on Mesh
4. Export the DEM into the TIFF format
5. Make an Orthophoto.
6. Create Terrain in Virtual Surveyor using DEM and Ortho

And, the result should be model with cut off parts higher than what was specified in Ground Points Filter.. We have the walls not the roofs of our houses..

That's just an idea, I'll test it right away.

Anyway, try Virtual Surveyor, it works fine beside that 2.5D and is free for the tryout period.

Regards,
Darko

Shovelhead

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Heres the link of how Pix4d handles digitization...https://youtu.be/AUSFDKncmJw
After a bit of digging it seems agisoft is not capable of doing this. Which leads me to believe that agisoft is not a viable option for survey mapping. If a client wanted a topographic plan and there was anything on the land I don't see how you would accurately display that to them.

Alexey Pasumansky

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Hello Shovelhead,

I still don't get what you are trying to achieve, can you describe it in some other way?

In PhotoScan you can draw polyline/polygon shapes in model view on point cloud or mesh model and later, if necessary, you can adjust the vertices of the drawn shapes on the original photos. Shapes can be exported in KML/DXF/SHP formats, but there's no automatic vectorization instruments at the moment, except the elevation contours generation.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Shovelhead

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Hello Shovelhead,

I still don't get what you are trying to achieve, can you describe it in some other way?

In PhotoScan you can draw polyline/polygon shapes in model view on point cloud or mesh model and later, if necessary, you can adjust the vertices of the drawn shapes on the original photos. Shapes can be exported in KML/DXF/SHP formats, but there's no automatic vectorization instruments at the moment, except the elevation contours generation.

That is exactly what I want to do. How do I do it?

Shovelhead

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Re: Most effective way to create survey site plans using photogrammetry?
« Reply #10 on: May 07, 2017, 06:05:41 AM »
If you skip to the 10:00 mark in this video https://www.youtube.com/watch?v=eWjll2ffdeY
That is exactly what I want to do.

stihl

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Re: Most effective way to create survey site plans using photogrammetry?
« Reply #11 on: May 07, 2017, 11:23:27 AM »
Hi Shovelhead,

Surveyor here for 7 years and using photoscan for 5 years.

From experience I can tell you that the absolute accuracy you can achieve with photoscan is higher than pix4D.
This is because photoscan allows more user input such as filtering of tie-poinrs and more extensive model build parameters.

The things you've seen in the link you posted can also be done in Photoscan by simply using the polyline or polygon tool on the toolbar in the photoscan interface. You can directly draw lines in the point cloud or in the mesh model and export these directly to a shapefile or kml/kmz.

Shovelhead

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Re: Most effective way to create survey site plans using photogrammetry?
« Reply #12 on: May 07, 2017, 11:18:20 PM »
Thanks for all the help. I have figured it out with your tips. Any suggestions in navigating the model and digitizing? There is a lot of switching back and forth between views and the polyline tool and the pick tool. Is there a better 3d mouse I should be using?

stihl

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Re: Most effective way to create survey site plans using photogrammetry?
« Reply #13 on: May 08, 2017, 12:04:50 AM »
The spacebar on your keyboard acts as a hotkey, letting you toggle between navigation mode and polygon/polyline/single point mode. Any of the three will switch back to navigation mode once the spacebar is pressed.

karad

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Re: Most effective way to create survey site plans using photogrammetry?
« Reply #14 on: May 09, 2017, 09:01:27 AM »
Usefull :
1.  Nasrullah, A.R. (2016) Systematic analysis of unmanned aerial vehicle (UAV) derived product quality. Enschede, University of Twente Faculty of Geo-Information and Earth Observation (ITC)
2. Photogrammetric Computer Vision: Statistics, Geometry, Orientation and Reconstruction  2016,  Wolfgang Förstner (Author), Bernhard P. Wrobel (Author)
« Last Edit: May 09, 2017, 09:05:24 AM by karad »