Georeferencing (Sorry)

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landmeterbeuckx
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Re: Georeferencing (Sorry)

Post by landmeterbeuckx »

@martin : i myself thought it was poorly done. It is horrible to hear yourself speaking.

Concerning Gps : when trying to use control points with gps the best method is to measure your control points when you start with an average of 50 cycles, then when you finish your work do them again and take averages. Constellation, sun flares, communications,... have an influence on the results.

Because the z-value can difference within one or two centimeters it is best to choose a control point and take this height as the reference, then with a digital level or a total station calculate your other heights accoording to this one.

If i do a project where i know i'll have to come back later on, i also measure some control points attached to a wall or nails in the ground with a total station attached to the original gps points, this is the safest way.

Gps is a means of measuring but has to be controlled carefully and only used accordingly.
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Re: Georeferencing (Sorry)

Post by jmonell »

Great discussion. I’d like to know if anyone has any experience with large facilities and bringing them into a state plane coordinate system. My project is a large building, about 500 scans, comprised of 15 clusters. I’ve combined the clusters into a master project. I have multiple ground control points across 3 of the exterior clusters.

I’ve brought in the control for one of the clusters, and based on the updated coordinates I see in planar view, the scans in that cluster did move. But none of the other clusters moved, and the overall registration goes red when I update.

Does anybody have experience with multiple clusters? Should I bring in the coordinates at the workspace level? I’m running Scene 7.1 on scans generated by an S120 and X330.

Once again, thanks for thread. Great reading.

John
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Re: Georeferencing (Sorry)

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jmonell wrote: Sat Sep 22, 2018 2:42 am Great discussion. I’d like to know if anyone has any experience with large facilities and bringing them into a state plane coordinate system.
We just completed the field work of approximately 350 acres of topographic survey, with dense Hawaiian vegetation and trees, where the client wanted 1inch=20foot data collected on the ground, with 1foot contours. We used our Reigl VZ400i mounted on our Riegl VMZ base with a Trimble R10 GNSS on the VZ400i as our positioning sensor running in RTK mode with 6 other Trimble R10 to pick up detailed objects and trees greater than 12 inches trunk diameter.

From the approximately 320 scan positions, we collected 2.5Billion points, converted the point clouds into Hawaii State Plane, Zone 3, geoid12B using Riegl RiScan Pro version 2.6.2 and checked the objects determined by the other 6 Trimble R10 sensors.
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Re: Georeferencing (Sorry)

Post by landmeterbeuckx »

jmonell wrote: Sat Sep 22, 2018 2:42 am Great discussion. I’d like to know if anyone has any experience with large facilities and bringing them into a state plane coordinate system. My project is a large building, about 500 scans, comprised of 15 clusters. I’ve combined the clusters into a master project. I have multiple ground control points across 3 of the exterior clusters.

I’ve brought in the control for one of the clusters, and based on the updated coordinates I see in planar view, the scans in that cluster did move. But none of the other clusters moved, and the overall registration goes red when I update.

Does anybody have experience with multiple clusters? Should I bring in the coordinates at the workspace level? I’m running Scene 7.1 on scans generated by an S120 and X330.

Once again, thanks for thread. Great reading.

John
John,
Look at this thread. https://laserscanningforum.com/forum/vi ... 495#p71495

You have to make a master cluster above your clusters and insert the reference there. Do a place scans with targets and it should work.
dhirota wrote: Sat Sep 22, 2018 3:32 am
jmonell wrote: Sat Sep 22, 2018 2:42 am Great discussion. I’d like to know if anyone has any experience with large facilities and bringing them into a state plane coordinate system.
We just completed the field work of approximately 350 acres of topographic survey, with dense Hawaiian vegetation and trees, where the client wanted 1inch=20foot data collected on the ground, with 1foot contours. We used our Reigl VZ400i mounted on our Riegl VMZ base with a Trimble R10 GNSS on the VZ400i as our positioning sensor running in RTK mode with 6 other Trimble R10 to pick up detailed objects and trees greater than 12 inches trunk diameter.

From the approximately 320 scan positions, we collected 2.5Billion points, converted the point clouds into Hawaii State Plane, Zone 3, geoid12B using Riegl RiScan Pro version 2.6.2 and checked the objects determined by the other 6 Trimble R10 sensors.
Dennis : did you do a semi mobile mapping measurement with the use of the vmz base?
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Re: Georeferencing (Sorry)

Post by dhirota »

landmeterbeuckx wrote: Sat Sep 22, 2018 10:07 am
Dennis : did you do a semi mobile mapping measurement with the use of the vmz base?
We used the Riegl VMZ base/rack/power distribution to achieve what we decided was more efficient data collection using TLS versus MLS
to locate scan positions between the vegetation and trees. I believe that field data collection is always better in an air conditioned car with the outside temperature at 90degreesF. We controlled the VZ400i using an iPad Pro in Wifi mode, setting a scan position every 20 to 30 meters. This was much better than moving a tripod over a dusty dirt road or waist high grass.

We used software to merge 8 Reigl scan projects into a single 90GB LAS format file, which was then batched processed to remove the vegetation and trees to produce a ground file (36GB) and a 3meter grid of ground points (3MB) in 2.5 hours of processing from the 2.5Billion points.

The time between scan positions was dependent on the range. At 250 meter range, the scan time was 45 seconds, including color imaging, with the total time between scan positions including travel time of approximately two minutes. At 350 meters, the comparable times are 90 seconds and 3 minutes. The significant recent Riegl VZ400i firmware upgrade allows the capture of color images during the scanning. The fastest scan + imaging time we have tried on the VZ400i is 30 seconds.
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Re: Georeferencing (Sorry)

Post by gsisman »

jmonell wrote: Sat Sep 22, 2018 2:42 am Great discussion. I’d like to know if anyone has any experience with large facilities and bringing them into a state plane coordinate system. My project is a large building, about 500 scans, comprised of 15 clusters. I’ve combined the clusters into a master project. I have multiple ground control points across 3 of the exterior clusters.

I’ve brought in the control for one of the clusters, and based on the updated coordinates I see in planar view, the scans in that cluster did move. But none of the other clusters moved, and the overall registration goes red when I update.

Does anybody have experience with multiple clusters? Should I bring in the coordinates at the workspace level? I’m running Scene 7.1 on scans generated by an S120 and X330.

Once again, thanks for thread. Great reading.

John
John,

State Plane Grid coordinates are calculated at Sea Level. Therefore if your site is above or below sea level your scan coordinates and thus the building scan would have to be scaled using a combined scale factor. At our D.O.T. we want all our projects to be tied into SPC but we would use and require a State Plane Control coordinate established at a general centroid position of the project and held as the scaling point where the SPC coordinate and the actual Ground coordinate (Project coordinate were the same). Then all GPS /SPC derived control points would be scaled from that point using the combined scale factor. Using this method your residuals from your scan cloud points to the Control tieing down the building should be at a minimum.

That being said. There is some issues in modeling programs like Revit That use scan clouds or structures derive from scan clouds- that cannot handle the many digits usually of the State Plane Coordinate systems- as the RAW data from the scanner is usually registered to a master scan which has 0,0,0 as its origin.

One of the questions I have is for anyone out there- How do the exports from a Registered mutli-station scan cloud bundle (ie PTX, E57, LAS, etc) carry that transformation/Registration to Grid information? Is there a header with information telling the XYZ shift and rotation and allowing the receiving software to make the shift applying this information to the actual coordinate points that are in Scan-cloud format? Or are the hundreds of millions of points stored with their 12-16 digit coordinate values? It seems the latter would force the file size to be exponentially bigger because of the extra bytes required to store those extra characters on each scan point.
I'm thinking perhaps the former (at least for E57) because we had an earlier registered point cloud (to SPC cordinates successfully applied in Register 360) exported in E57 and it not be recognized by recap software in State Plane Coordinates, so perhaps the header info was not recognized.
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