Georeferencing (Sorry)

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James Hall
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Re: Georeferencing (Sorry)

Post by James Hall »

Hello David.
I can’t speak to the use of Faro software. I’ve always used Leica, but I have worked with Military Grid Reference System a variant of UTM. UTM uses a similar coding for their points. UTM “10 N 706832.000 4344683.000” vs MGRS “10S GJ 06832 44683” vs Lat Long “39°13′36.5381″N, 120°36′13.9834″W”

With Leica Cyclone I recommend using meters as your units and setting up your coordinates based on the UTM grid your in. The 10S dose not matter to Cyclone and the coordinates are easting and northing with .000 to get you to millimeter accuracy.

When I write out my point files is when I would have added in the 10S zone for each point coordinate.

I don’t know if Faro is just reading the coordinates like Cyclone or is truly georeferencing the location like C3D.

https://en.wikipedia.org/wiki/Universal ... ate_system

https://www.movable-type.co.uk/scripts/ ... -mgrs.html

MGRS is a Meter only system and so is UTM. The zones are designate 100,000-meter square identification grids except for the north and south pole.
UTM is not supported as well as State Plane in some software packages. I would take the control points and convert them into Lat Long, UTM and state plane. Load them into Faro and compare the locations to make sure everything is coming in right.
Cad programs like AutoCAD Civil 3D allow you to write out KMZ files of your coordinates to check your work in Google Earth. Earth Point website can also help plot location and compare. http://www.earthpoint.us/

Is your Raw data in UTM?
James,
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Re: Georeferencing (Sorry)

Post by ddustin »

James Hall wrote: Thu May 31, 2018 3:14 pm Is your Raw data in UTM?
James,
James, thank you for your well thought out response.
I would say not it isn't by default (but can't say that with absolute certainty).

The military "10 Grid" looks interesting and I'm reading up on it now.

Thanks everyone!
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Re: Georeferencing (Sorry)

Post by Graham »

Oatfedgoat wrote: Thu May 31, 2018 12:29 pm
Graham wrote: Thu May 31, 2018 11:09 am

It is difficult as metadata on surveys seems to be the first thing that is lost, if we could embed this data into the scan it would be best but we are were we are.
It would be fantastic if software systems started to introduce a field of metadata for accuracy.
I would go as far as wanting it to be an attribute to the file, whether that file is a processed traverse in starnet, a processed survey in N4ce etc, A topo survey in AutoCAD or a full BIM in Revit.
Maybe e57 is the only likely option where it could happen for point clouds?

This would massively help ensure that the accuracy and therefore useability of a survey is never lost as well as help with audit and assurance trails/reports.
The LAS format already has metadata attributes for the projection yet I see National Mapping Agencies delivering data with this not populated. My pet annoyance is failing to define the linear unit, when the data is not geo-referenced.

I cannot comment on E57 header blocks, I a sure there are members of the forum that contribute to this format.
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Re: Georeferencing (Sorry)

Post by landmeterbeuckx »

I'll try to make a video with a few scans. Give me some time as i am not a video artist :D

I'm glad i can give some of my knowledge back to people who have taught me everything about faro scene when i started with it.

In a few days i'll post a small video.
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Re: Georeferencing (Sorry)

Post by James Hall »

Hello David,

I forgot to mention that UTM can measure distances down to .000 of a meter, But MGRS will only measure down to a meter. MGRS can be truncated to divided up the 100,000-meter square identification grids "zones" in to 1,10,100, and 1000 meter grids. This system is optimized for Radio broadcast of your position. I guess if they can drop a bomb within a meter that is close enough.

James
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Re: Georeferencing (Sorry)

Post by landmeterbeuckx »

I was fast for once. I made a basic video. If you have any questions just ask.

My apologies for the poor sound quality but you'll get it i think.

youtu.be/K8Wf9gwu0ZU
https://www.youtube.com/watch?reload=9&v=K8Wf9gwu0ZU

The image quality isn't that good. You can download the same through this link
https://we.tl/UtWjTwU0km
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Re: Georeferencing (Sorry)

Post by dhirota »

landmeterbeuckx wrote: Thu May 31, 2018 1:48 pm The height with gps is absolutely not reliable. Even with rtk one has to measure each control point with a total station or even better a digital level. You take one measurement as reference for z and refer the rest to this one. Differences with rtk of several cm's are not uncommon.

Gps has to be taken in open canopy and under different constellations to be sure to be used.

With a riegl it is easier, you just put the rtk on top and do not have to worry about anything else. I do take control points for control.

Surveying is control and control and control...
Having a Riegl VZ400i makes this much easier.

viewtopic.php?f=69&t=13018

VZ400i-TRIMBLE-R10_IMG_0250.jpg

VZ400i_IMG_0256.jpg

Riegl uses GeoSysManager utility software to convert LAT/LONG scan position to other world coordinate systems.

An example of Z (elevation) problems with GNSS information is the OPUS report for our Trimble R9 base station which deviates approximately 2 ft from the monument elevation, but less than 10mm in X, Y position.


OPUS solution _IGS000USA_R_20181261945_01D_15S_MO.rnx OP1525724177820_Page_1_1K_VERT.jpg
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Georeferencing (Sorry)

Post by Felix_the_Cat »

landmeterbeuckx wrote:
EDIT : if anyone is interested i want to make a small screen recording of how it's done in scene.
YES!

I am exceptionally interested please.

Edit: Whoops! You already did. I didn't make it that far when I posted this. Thanks!!!!


Sent from my iPhone using Tapatalk
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Re: Georeferencing (Sorry)

Post by landmeterbeuckx »

dhirota wrote: Thu May 31, 2018 7:00 pm

Riegl uses GeoSysManager utility software to convert LAT/LONG scan position to other world coordinate systems.

An example of Z (elevation) problems with GNSS information is the OPUS report for our Trimble R9 base station which deviates approximately 2 ft from the monument elevation, but less than 10mm in X, Y position.



OPUS solution _IGS000USA_R_20181261945_01D_15S_MO.rnx OP1525724177820_Page_1_1K_VERT.jpg
Dennis,

We don't have to work with base stations anymore. All ground is covered with permanent gps-stations (Flepos and Walcors systems) for RTK use.
Critical points are always being measured at the start and then at the end of the survey because of a complete different constellation. I use GPS in combination with Glonass.

One control point can be enough to detect vertical errors.

Geosysmanager works great indeed.

Lieven
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Re: Georeferencing (Sorry)

Post by VXGrid »

I'd like to add a thought to the accuracy mentioned by Scott Warren:
As I know it is possible to buy GPS improving data some days/weeks later due to the fact that the positions of the satellites can be determined more accurate some time later.
So with postprecessed GNSS data the accuracy should improve even further.

In addition: In Germany you don't need your own station for RTK, one could use SAPOS instead, I'm sure there is something similar in other countries.

@Lieven: Nice video!
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