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Deep Dive into TransformationsBojan Šavrič & Melita Kennedy
Demo in ArcGIS Pro
Where is my
transformation?
Why do we need to transform our data?
WGS 1984
ED 1950
WGS 1984
ED 1950
Why do we need to transform our data?
Geographic (datum) transformation
Vertical transformation
Two Kinds of Transformations
• Between two geographic
coordinate systems:
Geographic (Datum) Transformations
Source: GURS
D48 (old datum)
D96 (new datum)
Geographic (Datum) Transformations
Source: GURS
• Multiple transformations
D48 (old datum)
D96 (new datum)
Geographic (Datum) Transformations
Source: GURS
• Multiple transformations
- Various areas, extents
D48 (old datum)
D96 (new datum)
Geographic (Datum) Transformations
Source: GURS
• Multiple transformations
- Various areas, extents
- Different accuracies
D48 (old datum)
D96 (new datum)
Geographic (Datum) Transformations
Source: GURS
D48 (old datum)
• Multiple transformations
- Various areas, extents
- Different accuracies
D96 (new datum)
How do I find transformations?
Transformation List
• Envelope intersections
- Data
Source: GURS
Transformation List
• Envelope intersections
- Data
- Geographic CS
Source: GURS, EPSG
Transformation List
• Envelope intersections
- Data
- Geographic CS
- Transformations
Source: GURS, EPSG
Transformation List
• Envelope intersections
- Data
- Geographic CS
- Transformations
Source: GURS, EPSG
Transformation List
• Envelope intersections
- Data
- Geographic CS
- Transformations
Source: GURS, EPSG
• Envelope intersections
• Accuracy
Transformation List
Source: GURS, EPSG
• Envelope intersections
• Accuracy
• Resource:
- EPSG (epsg-registry.org)
- Government agencies
Transformation List
Source: GURS, EPSG
Demo in ArcGIS Pro
Geographic (Datum)
Transformations
Vertical Transformations
Ellipsoidal Heights (NAD83)
Orthometric Heights (NAVD 88)
NAD_1983_To_NAVD88_
CONUS_GEOID12B_Height
The Origin for Height or Depth
• Ellipsoidal height (h)
- Geometric datum
• Gravity-related height (H)
- Vertical datum, e.g. geoid
• Between ellipsoidal and gravity-related heights
• Used with GNSS
Types of Vertical Transformations
GCS A / VCS A
GCS A / VCS 2
Vertical transformation
using geoid model
• Between ellipsoidal and gravity-related heights
• Used with GNSS
Types of Vertical Transformations
NZGD2000_To_
NZVD2016_Height_1
NZGD 2000 / NZGD 2000
NZGD 2000 / NZVD 2016
• Between two geographic coordinate systems
• Heights are ellipsoidal
Types of Vertical Transformations
GCS B / VCS B3D Geog. Transformation
GCS A / VCS A
• Between two geographic coordinate systems
• Heights are ellipsoidal
Types of Vertical Transformations
GDA 2020 / GDA 2020GDA_1994_To_GDA2020_1
GDA 1994 / GDA 1994
• Between two gravity-related heights
Types of Vertical Transformations
Vertical
Transformation
GCS A / VCS 1
GCS A / VCS 2
• Between two gravity-related heights
Types of Vertical Transformations
Baltic_To_Caspian_1
Pulkovo 1942 / Baltic 1977
Pulkovo 1942 / Caspian Sea
• Between two gravity-related heights
• May require interpolation GCS
Types of Vertical Transformations
GCS A / VCS 1
GCS A / VCS 2
• Between two gravity-related heights
• May require interpolation GCS
Types of Vertical Transformations
GCS C / VCS 12D Geog. Transformation
GCS A / VCS 1
GCS A / VCS 2
• Between two gravity-related heights
• May require interpolation GCS
Types of Vertical Transformations
Vertical
Transformation
GCS C / VCS 1
GCS C / VCS 2
2D Geog. TransformationGCS A / VCS 1
GCS A / VCS 2
• Between two gravity-related heights
• May require interpolation GCS
Types of Vertical Transformations
Vertical
Transformation
GCS C / VCS 1
GCS C / VCS 2
2D Geog. TransformationGCS A / VCS 1
~2D Geog. TransformationGCS A / VCS 2
Demo in ArcGIS Pro
Vertical
Transformations
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD 83 (2011)
NAD 1927
NGVD 1929
NAD 83 (2011)
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD_1927_To_NAD_1983_NADCONNGVD 1929
NAD 1927
NGVD 1929
NAD 1983
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD_1927_To_NAD_1983_NADCON
NGVD29_To_NAVD88_NAD83_ECW
NAD 1927
NGVD 1929 NAVD 1988
NAD 1983
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD_1927_To_NAD_1983_NADCON
NGVD29_To_NAVD88_NAD83_ECW
~NAD_1983_To_NAVD88_CONUS_GEOID12B_Height
NAD 1927
NGVD 1929 NAD 1983
NAD 1983
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD_1927_To_NAD_1983_NADCON
NGVD29_To_NAVD88_NAD83_ECW
~NAD_1983_To_NAVD88_CONUS_GEOID12B_Height
~WGS_1984_(ITRF00)_To_NAD_1983
NAD 1927
NGVD 1929 WGS 1984
WGS 1984
Why couldn’t we transform a layer?
• Restricted to four (4) steps in a path
- 2 geographic
- 2 vertical
NAD_1927_To_NAD_1983_NADCON
NGVD29_To_NAVD88_NAD83_ECW
~NAD_1983_To_NAVD88_CONUS_GEOID12B_Height
~WGS_1984_(ITRF00)_To_NAD_1983
WGS_1984_(ITRF08)_To_NAD_1983_2011
NAD 1927
NGVD 1929 NAD 83 (2011)
NAD 83 (2011)
ArcGIS
Coordinate
Systems
Data
ArcGIS Coordinate Systems Data
• 1.6 GB additional data install
• GEOCON v1.0 (USA)
• NTv2 (AU, BE, CA, ES, CH, UK)
• NADCON (SK)
• VERTCON / GEOID12B (USA)
• Geoids (JP, NZ, CH)
• EGM2008 (world)
Geographic
Transformations
Vertical
Transformations
Resources
• Esri Projection Engine Database Documentation
- https://github.com/Esri/projection-engine-db-doc/
Resources
• Don't forget the Knowledge Base / Technical Articles!
- http://esriurl.com/11518
• Esri forums for user-to-user help
- http://geonet.esri.com
• EPSG (epsg-registry.org)
- Database of coordinate systems & datums
- Guidance Note 7-2
• Lining Up Data in ArcGIS, Margaret Maher
Hands-on Learning Lab, Exhibit Hall A
Today, 9:00 am – 4:00 pm
Spatial Reference and
Data Alignment Lesson
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