I am being tasked to provide control for a SfM project. Area is remote, hard to reach and we have enough survey grade receivers to allow 2 hour OPUS solutions in the project area. I'm looking for guidance, to achieve 10-20 cm vertical and the spacing for Ground Control to achieve this. We will have some opportunity to premark with panels and some RTK will be available for a short time (via skiffs) for check shots. But due to distances, I'm looking for the spacing I can rely on when the plane is flying overhead, and since were not getting back to this area until the next summer at best, what is the distance between points to tie this down to earth. Our CORS network is very good in this area with typical 20- 70 miles - excellent for Alaska.
Guidance, documents that include tables specific for SfM postprocessing including ground control is what i'm seeking. This is a coastal fringe product, where there is plenty of open sky, but tight time constraints, so planning this effort is falling a bit on my back.
Thanks.
Joel if this is the SFM project in Denali NP be very careful using GPS for heights! You are next to the largest local attraction mass in North America and even though the NGS gelid models are improving, the mountain that goes from sea level to 20,000 feet in a few miles is way hard to model the deflection from vertical. The airborne gravity grid density is too coarse to model the local effects. You may want to do a GPS control network with post processed vectors put in a properly weighted Least Squares adjustment constrained vertically to the leveled benchmarks, not OPUS. Part of the issues you are seeing with ground truthing the previous SFM data was the airborne sensor processing likely only used a GPS derived orthometric elevations with applied geoid model corrections. Believe me, I learned this in the 80s when we were trying to use gravity models for INS processing. Later in the 90s I spent a whole lot of time and hair pulling trying to do the computations for the first GPS height determination of the summit. We couldn't have the climbing team pack a gravitomiter to the summit. We did do gravity measurements bracketing the summit for our other control stations. It's really a challenge to get 10cm ortho heights around Denali, may be not even possible with GPS only. Certainly RTK is out of the question.
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What is a SFM project?
leegreen, post: 425453, member: 2332 wrote: What is a SFM project?
Apparently....
Serious
F&*%ing
Mass
I don't know if "Structure from Motion" and "Structure for Motion" are the same thing or not, but this paper and the references in it may help.
http://www.sciencedirect.com/science/article/pii/S0169555X12004217
From the ground view: https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/41413.pdf
leegreen, post: 425453, member: 2332 wrote: What is a SFM project?
Structure From Motion. Its a photogrammetric procedure where control is passed from pixel to pixel. Most commonally used with small to medium format cameras. Amazing stuff.
https://en.wikipedia.org/wiki/Structure_from_motion
Agisoft Photoscan software is a leader in the processing of SFM data: agisoft.com
Still pretty general, but this may provide a contact for you as well as some information:
Thanks all.
Michael, the job is west side Cook Inlet. Mark Laker, and Seth(BLM) are both the reason we're going this route. They held two seminars out of Kenai. I'm leaning to have as much redundancy as possible. We're exploring use of bio degradable chalk for pre-marks for GCP's eliminating panel hassle and curious brown bears. Attempting this at low tide too, so wet mud will be very common. Looking for more details on ground control guidance. Thanks for input.
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From my experience, if your trying to adhere to USGS National Map Accuracy standards for 1-foot contours, you'll need to place GCP's no
more than 1/2 a mile apart with even distribute at the corners and points on the interior of your project boundary. With proper photogrammetric adjustments you should be able to obtain less than 0.25' vertical accuracy.
The Alaskans with a preponderance of aircraft, pilots and the McGuyvers who are willing to cut a hole in the bottom of aircraft are really pushing the limits of Structure from Motion. Manned and Unmanned.
Take a look at the arctic science using SfM on ice/snow.?ÿ?ÿ https://www.researchgate.net/publication/273310002_Mapping_snow-depth_from_manned-aircraft_on_landscape_scales_at_centimeter_resolution_using_Structure-from-Motion_photogrammetry
NPS has done some amazing projects this year.?ÿ Fairbanks Fodar had a busy summer too including the massive 1002 area.?ÿ http://fairbanksfodar.com/how-i-spent-my-summer-vacations and?ÿ http://fairbanksfodar.com/1002-mapping-nearly-complete
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The Alaskans with a preponderance of aircraft, pilots and the McGuyvers who are willing to cut a hole in the bottom of aircraft are really pushing the limits of Structure from Motion. Manned and Unmanned.
Take a look at the arctic science using SfM on ice/snow.?ÿ?ÿ https://www.researchgate.net/publication/273310002_Mapping_snow-depth_from_manned-aircraft_on_landscape_scales_at_centimeter_resolution_using_Structure-from-Motion_photogrammetry
NPS has done some amazing projects this year.?ÿ Fairbanks Fodar had a busy summer too including the massive 1002 area.?ÿ http://fairbanksfodar.com/how-i-spent-my-summer-vacations and?ÿ http://fairbanksfodar.com/1002-mapping-nearly-complete
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The Alaskans with a preponderance of aircraft, pilots and the McGuyvers who are willing to cut a hole in the bottom of aircraft are really pushing the limits of Structure from Motion. Manned and Unmanned.
Take a look at the arctic science using SfM on ice/snow.?ÿ?ÿ https://www.researchgate.net/publication/273310002_Mapping_snow-depth_from_manned-aircraft_on_landscape_scales_at_centimeter_resolution_using_Structure-from-Motion_photogrammetry
NPS has done some amazing projects this year.?ÿ Fairbanks Fodar had a busy summer too including the massive 1002 area.?ÿ http://fairbanksfodar.com/how-i-spent-my-summer-vacations and?ÿ http://fairbanksfodar.com/1002-mapping-nearly-complete
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Joel
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