https://github.com/chasmack/arcgis-coord-transform
Local coordinate transforms for ArcGIS Pro
https://github.com/chasmack/arcgis-coord-transform
arcgis-pro coordinate-transformations local-coordinates python-toolbox similarity-transformations
Last synced: 3 months ago
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Local coordinate transforms for ArcGIS Pro
- Host: GitHub
- URL: https://github.com/chasmack/arcgis-coord-transform
- Owner: chasmack
- Created: 2018-12-12T21:13:13.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2020-01-20T23:20:04.000Z (over 5 years ago)
- Last Synced: 2025-01-12T13:14:43.352Z (4 months ago)
- Topics: arcgis-pro, coordinate-transformations, local-coordinates, python-toolbox, similarity-transformations
- Language: Python
- Size: 313 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
### ArcGIS Coordinate Transform
Projected geographic coordinates have several advantages for the land surveyor.
Geographic points and linework drop directly onto aerial imagery and inexpensive handheld
GPS receivers can be used for search.
However many small and medium size projects use local coordinates, ground distances
and true or record bearings. Local coordinates are familiar, and mapping is often
recorded with a true or record basis of bearings.
The ArcGIS Pro tools in this project provide a link between the local project coordinates
and projected geographic data in a GIS project.
The tools use the geoprocessing environment variables `workspace` and `outputCoordinateSystem`.
The tools also assume points are saved in a Feature Dataset called Points and use a
Feature Class template called Points\PointsTemplate. Initialize the points templare
from the ArcGIS Pro Python window -
sys.path.insert(0, r'D:\Projects\Python\ArcGIS_Coord_Transform')
from tools.utils import create_points_template
create_points_template()
Start by creating project boundaries and other features using traditional CAD tools.
Create points and export a PNEZD points file. Import these local points into an ArcGIS
geodatabase with the Import PNEZD tool using no transform.
Next, set up an ArcGIS Pro project using an appropriate projected coordinate system.
Create a feature class with one or more projected geographic points in the ArcGIS project.
These points represent the target positions for corresponding local points. Initially this
might be a rough location picked from an aerial image or geographic coordinates from a map
or GPS shot. A single point and rotation will be enough to get started.
Now use the Calculate Transform tool to generate the four-parameter transform file used to
import points and linework into the ArcGIS project. Input for the Calculate Transform tool
can be entered manually or placed into a Transform.xml parameter file. In many cases transform
parameters will be recalculated as more accurate geographic positions become available.
Finally, use the Import CAD and Import PNEZD tools with the transform parameters to create
feature classes and transform coordinates to the projected coordinate system. If in the future
the transform in updated features can either be reimported using the new transform parameters
or run through the Transform Features tool, once using the old transform parameters in the
Inverse direction and again using the new parameters in the Forward direction.
The parameter file has the four parameters for a similarity transform: x/y translation,
rotation and scale. They are expressed as a0, b0, a1, b1 where -
a1 = scale * cos(rotate)
b1 = scale * sin(rotate)
a0 = x1 - a1 * x0 + b1 * y0
b0 = y1 - b1 * x0 - a1 * y0