2. Using CAD Parcel data with the Local Government Solution
July 25, 2012
Using CAD Parcel data with the Local Government Solution
Chris Buscaglia & Amir Bar-Maor

3. CAD Parcel Data Characteristics
Computer Assisted DRAFTING
File based and static
Usually not spatially referenced
Attribution as floating text (annotation)
Line based  overshoots & undershoots
Contains unnecessary geometries (map elements)
Layer structure is not consistent
Does not contain Tax Parcels
Designed for drafting

4. Ground to Grid Correction
Ground: the measurements as they are captured by the surveyor on the ground. The direction might be relative to several definitions of north.
Grid: a projected coordinate system on the ellipsoid. E.g.: State plane
Ground to Grid Correction: scale & rotation

5. CAD Integration Methods
Method 1: The Ad Hoc Method
Method 2: The Systematic Method

6. The Ad Hoc Method Ad hoc steps Add CAD Data Select Lines Copy & Paste
Clean &
Build
Join
Attribute
Parcels
Ground to Grid

7. The Ad Hoc Method With small datasets (less than 1,000 lines) because:
When should I use it?
With small datasets (less than 1,000 lines) because:
Hard to fix errors on a large dataset
Hard to join a large dataset
Not limited to CAD lines
Attention:
Measurements are calculated during construction (ground)  do not georeferenced the CAD file if it is in ground

8. Ad Hoc Method
Chris Buscaglia
DEMO

9. The Ad Hoc Method Easy Fast Good for a small dataset (few parcels)
Pros
Easy
Fast
Good for a small dataset (few parcels)
Ability to manually correct the COGO dimensions for each line

10. The Ad Hoc Method Limited to a few parcels (1,000 lines)
Cons
Limited to a few parcels (1,000 lines)
Might be time consuming to fix many line errors
Line category has to be set manually
Need to set parcel type and name manually
… It might be just as fast to re-COGO

11. The Systematic Method Systematic Method Steps for a subdivision
Copy Lines
to Staging GDB
add COGO Attributes
Filter Out
Unnecessary
lines
Use Topology to
Clean Lines
Calculate
COGO
Prepare
Line
Attributes
Separate
Lines by
Parcel Type
Import Parcel
Names as
Annotation
Create
Polygons
Attribute
Polygons
Create Topology
& Import Subdivision
As Unjoined
Join
Subdivision
Import & Join
Lot Parcels

12. The Systematic Method Large datasets
Why use this method
Large datasets
QA and analyze the data in a staging environment
Preserves COGO-ed dimension
Efficient attribution for parcel names
Ability to improve geometry using geoprocessing tools and Add-ins (e.g. curves)
Similar to a migration process
Can be streamlined using a geoprocessing model

13. Systematic Method
Chris Buscaglia
DEMO

14. The Systematic Method Captures parcel attributes
Pros
Captures parcel attributes
Can be automated and streamlined
Scalable—Can process thousands of parcels at a time

15. The Systematic Method Involves more steps
Cons
Involves more steps
Not cost effective for only a few parcels

16. Methods Comparison Parameter/Method Ad Hoc Systematic
Size: Few parcels
Recommended
Too much effort unless automated
Size: Many parcels
Limited
Good
COGO attributes
Preserved
Automation
Not possible
Possible when data is structured
Parcel attributes
Have to be entered manually
Can be obtained from annotation
Digital submission standard does exist

17. Why Maintain Your Measurements (COGO)?
Ability to use labels or feature linked annotation.
Eliminate the need to go to the clerk's office to get legal dimensions
QA the data you receive: misclosures, rotation…
Maintain accuracy and run a meaningful least squares analysis (LSA).
Stated Area is calculated from COGO.
Misclosure is stored and based on COGO.
Categorize your lines correctly: boundary, road frontage…

18. Best Practices Use a digital submission standard
Update the pasted geometry with the record values

19. Road Ahead: 10.1 SP1
Automated workflows for maintaining Parcels

20. 10.1 SP Automated Workflows
Parcel Workflows
10.1 SP1 – even easier, more streamlined
LGIM enabled Parcel Fabric available with the core ArcGIS system
Workflows available with the core ArcGIS system, upgrade available at 10.1 SP1

21. Road Ahead 10.1 SP1
Amir Bar-Maor
DEMO

22. UC Presentations Technical Workshops
Sessions to attend
Technical Workshops
Editing Parcels with the Local Government Information Model Thursday, 8:30 - 9:45
Demo Theaters
Creating a Tax Map using the Local Government Solution Thursday, 11:00 – 11:30

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