CSRS Coordinate Systems

[gingerbreadman]

Hello,

I have recently applied the version 2 of the Canadian National Transformation (https://knowledge.autodesk.com/support/autocad-map-3d/troubleshooting/caas/sfdcarticles/sfdcarticles...) to Civil 3D 2020.  When applying the free Bing Image from the Geolocation tab, I noticed that there's an approximate 20 m difference between UTM83-17 (UTM NAD83 Original) and CSRS.UTM-17N (UTM NAD83 CSRS).  I'm not a coordinate system expert, but my understanding is the difference between UTM NAD83 Original and UTM NAD83 CSRS in anywhere between a couple of cm to 2 m max.  Would anybody happen to know if this imagery is being displayed correctly or confirm that the difference between these two coordinate systems is truly around 20 m (any documentation supplied with this confirmation would be appreciated)?

Thanks,

Jay

[Pointdump]

Jay,
"...approximate 20 m difference between UTM83-17 (UTM NAD83 Original) and CSRS.UTM-17N (UTM NAD83 CSRS)."
Not surprising. I've seen as much as 70M shift between NAD83 and CSRS.
And each Province even has its own local version of the National Grid Shift File. >>>Link<<<
Not much you can do about Bing Live Maps. You're better off searching for some fresh Imagery from Government Sources. (They fly aerial panels every year to catch building permit scofflaws.)
Dave

[gingerbreadman]

Thanks for the info, Dave -this is very interesting.  I'll see if I can find something surveyed in CSRS.UTM-17N (UTM NAD83 CSRS) to compare against or may have to resort to purchased imagery to perform the comparison.

Thanks again,
Jay

[jae.kwon]

I thought geomap doesn't provide elevations?

[ChicagoLooper]

If you have  installed the Canadian NTv2 and want to compare UTM83-17 vs CSRS.UTM-17N then you can do it but you must compare apples-to-apples and not apples-to-bananas.

Experiment:

(1) While in Google Earth Pro place a pushpin at the intersection of Queensway E and Hurontario St. in the city of Mississauga, Ontario. The Lat/Long coordinates will be at, or near 43.574068, -79.607606. 

(2) Next, open two separate metric drawings: A and B.

Assign to A: UTM83-17 (EPSG 26917)

Assign to B: CSRS.UTM-17n (EPSG 2958)

(3) Place a Geomarker using Lat/Long coordinates into drawings A and B. (Go to Geolocation Tab=>Tools Panel=>Mark Position Dropdown=>Select Lat-Long option from dropdown). When placing the geomarker in drawings A and B, use the Lat/Long coordinates shown in step 1. The GEOMARKLATLONG command is shown below.

Place a geomarker using GEOMARKLATLONG.

(4) Turn on Bing Hybrid in both A and B. Next, select the geomarker in drawing A and write down or take screenshot of Properties Palette. Select the geomarker in drawing B, again, write down or take a screenshot of Properties Palette.

(A) UTM83-17 (EPSG 26917)(B) CSRS.UTM83-17N (EPSG 2958)

If you insert a point using Lat/Long degrees, then the result will be correctly positioned at the intersection of Queensway and Hurontario regardless of the assigned coordinate system. (See both Bing Hybrid images above.)

If you insert a point using X,Y meters, then you better know whether the X,Y coordinates are referenced against UTM83-17 or CSRS.UTM-17N, because if you don't then you will have issues with the position of the geomarker. These X,Y coordinates are not interchangeable, i.e. you cannot simply substitute one for the other. You must be cognizant when determining which one to use.

Whether Lat/Long degrees, UTM83-17 meters or CSRS.UTM-17N meters, ignoring the reference source is a no-no. It must be considered during input.

[Pointdump]

Jay,
Another good way to comparison check is to grab your Province's Survey Control Points. They will usually have not only good Coordinates and Metadata about the Projection and Datum, but also a sketch of the Control Point and nearby Features.
Dave

[lynn_zhang]

Hello @gingerbreadman ,

Just checking to see if your problem has been solved. Have you tried the suggestions from our experts above and did any of them work? Let us know if you still need help!

[Pointdump]

Jay,
Not sure why, but Bing now suffers from both position and resolution problems. More >>>Here<<<. You can shift the Bing Imagery using Matt Kolberg's way in >>>This Video<<<.
Dave

[jae.kwon]

Bing's never had good resolution compared to Google except for occasional pockets of rural spaces...

[gingerbreadman]

Hi Dave,

Thanks for looking into that -this is very good to know!  I've never fully trusted Bing Imagery as I'm aware it's free imagery and "we get what we pay for" but the odd thing is the imagery projects fine when applying other coordinate systems in the exact same area (ex. UTM NAD83, MTM NAD27, etc.) -it's only off with the CSRS coordinate systems I'm trying to apply (CSRS.MTM-10 and CSRS.UTM-17N).  I spoke with a surveyor regarding these CSRS coordinate systems and for where he's located (which is approx. 140km from the site I'm working on) the difference between UTM NAD83 and UTM NAD83 CSRS is about 0.4 m in the x, y plane.  Very different value from the near 20 m difference I'm getting.  I also asked a colleague of mine to perform the same translation in ESRI ArcMap and the difference between the the original dataset and the transformed dataset is approx. 0.15 m . 😞

[ChicagoLooper]

If you know how, input your coordinates in Lat/Long DEGREES, not in x,y meters. If you can't then you will be subjected  to your 20m difference and without a workable solution. 

[Pointdump]

Jay,
Thanks for posting about this. I'm questioning my assumptions about what is shifting. Using the suggestion from @ChicagoLooper , I exported Control Point #775019(Nipawin, Saskatchewan) as Decimal Lats and Longs(to the maximum 17 decimal places). In QGIS I saved that point in 2 Projections:

EPSG:2957
NAD83(CSRS) / UTM zone 13N

EPSG:26913
NAD83 / UTM zone 13N

Open 2 empty Metric Drawings, assigning one of the above Coordinate Systems to each drawing. Drag-n-Drop both of the attached shapefiles into each drawing. In the CSRS drawing you get two points 31 Meters apart. In the NAD83 drawing both points land in the same spot.
What to make of this? I dunno.

[ChicagoLooper]

Hi @Pointdump ,

Thanks for following along. We are both cynical skeptics.

What are the Lat/Longs of the red and yellow points the the C3D drawing using CSRS.UTM-13N?

In the C3D drawing using UTM83-13, both the red and yellow points have the same Lat/Long AND the same x,y coordinates (cartesian). This is how it should be, correct?

Just curious, if you created a third C3D drawing using the coordinate system WGS84.Pseudo Mercator (EPSG 3857) with spherical geoid, then drag-n-drop the QGIS shapefiles, would the results be like image 1 (red & yellow apart) or image 2 (on top of one another)?

[Pointdump]

@ChicagoLooper,
"... using UTM83-13, both the red and yellow points have the same Lat/Long AND the same x,y coordinates (cartesian)."
That is EXACTLY the right question to ask, since Lats and Longs of same point on earth will be different for every Datum. Here is the workflow:
1. In C3D create a COGO Point in a UTM83-13 drawing:
N: 5906906.268
E: 566463.689
Z: 370.1993
2. Export Lat and Long to a text file and use that to create an LL84 Point in QGIS.
3. From QGIS, Export that point in 2 different Coordinate Systems:

EPSG:2957
NAD83(CSRS) / UTM zone 13N

EPSG:26913
NAD83 / UTM zone 13N

4. Drag-n-Drop those 2 shapefiles into drawings each assigned one of those CS's.

OK, so it gets weirder. When I Drag-n-Drop those 2 shapefiles into a drawing assign EPSG:3857, one of 'em lands in Europe.

Dave

[Pointdump]

Jay,
I thought I'd continue this topic over in the >>>Map 3D Forum<<<.
Dave

[ChicagoLooper]

Assign WGS84.PseudoMercator (EPSG 3857) to a brand new, clean metric template. Place a Lat-Long geomarker into modelspace. Use Lat=53.30717720625818856 and Long=-104.00252803403915891. Turn on Bing imagery. You will get this:

  

[ChicagoLooper]

---

@Pointdump wrote:

......... Drag-n-Drop those 2 shapefiles into drawings each assigned one of those CS's.

OK, so it gets weirder. When I Drag-n-Drop those 2 shapefiles into a drawing assign EPSG:3857, one of 'em lands in Europe.........

---

When you drag-n-drop the shapefile what is displayed under the Coordinate System column in the Data Connect Palette? Does it match the shapefile's prj file?

When you drag-n-drop are you given the opportunity to verify the correct CS is being used and whether an inappropriate CS was substituted against your wish?

[Pointdump]

@ChicagoLooper,
Thanks. I forgot to check after the Drag-n-Drop. But it's back to 2 points 31 Meters apart.

Dave