Jump to content

 
Photo

Simplifying river data

- - - - -

  • Please log in to reply
19 replies to this topic

#16
Rob

Rob

    Legendary Contributor

  • Moderator
  • PipPipPipPipPip
  • 418 posts
  • Gender:Male
  • Location:Kailua, Hawaii
  • Interests:anything outside.
  • United States

Have you tried MapShaper to edit the shapefiles first, before going into Illy? I've had pretty good results from it.

Charles Syrett
Map Graphics
http://www.mapgraphics.com

I'm back to working on the SRWP watershed atlas. Work involves importing NHD flow-line data into AI via MAPublisher. The layer is immense with every river, stream and creek shown in great detail. My first step in working with this data is to clean it up, reduce the number of anchor points and convert the segmented geometry to smooth bezier curves. I've been using the AI Path> Simplify command at 99% or 98% with some success, but overall I'm not happy with the results and would like to know if any one has some tips or tricks for working with data like this?

In particular I'm wondering if there is a way to automatically get rid of kick backs?

David


I'd suggest MapShaper too. I had the same issues with the simplify path command.

#17
Garvan

Garvan

    Contributor

  • Validated Member
  • PipPip
  • 12 posts
  • Location:Toronto
  • Canada

What is a kickback? I assume it is some artifact of line-to-bezier conversion. If you would like, post some data or send it to support@avenza.com, and we can take a look at in more detail.
Garvan Keeley
Software Development Manager
Avenza Systems Inc.

#18
David Medeiros

David Medeiros

    Hall of Fame

  • Validated Member
  • PipPipPipPipPipPipPip
  • 1,089 posts
  • Gender:Male
  • Location:Redwood City CA
  • Interests:Cartography, wood working, wooden boats, fishing, camping, overland travel, exploring.
  • United States

What is a kickback? I assume it is some artifact of line-to-bezier conversion. If you would like, post some data or send it to support@avenza.com, and we can take a look at in more detail.


A kick back is when the handles of a bezier curve are reversed creating a loop or kink in the line. When using the AI simplify command on segmented lines in a shape-file AI converts the straight lines to bezier curves giving them splines and handles. For whatever reason it sometimes flips the direction of one set of curve handles kinking the line. It's usually obvious but some of the kick backs look ok until you really get in there or try to apply special line effects to them.

Kick back may not be the correct term for this, I think I got it from my GIS classes.

The top line below shows and obvious kick back. The lower line shows one that is harder to see, but the center anchor point is reversed or flipped.

Attached Files


GIS Reference and Instruction Specialist, Stanford Geospatial Center.

 

www.mapbliss.com

 


#19
Garvan

Garvan

    Contributor

  • Validated Member
  • PipPip
  • 12 posts
  • Location:Toronto
  • Canada

Thanks for the explanation David.

In our experience this happens after a join operation, where overlapping paths were incorrectly handled, creating a loopback at the joining vertices.
We tried to recreate this on river data that has not been joined, and it didn't happen.

I'll file a feature request for a tool that rectifies this type of data, maybe we'll get to it if there is enough interest.
Garvan Keeley
Software Development Manager
Avenza Systems Inc.

#20
David Medeiros

David Medeiros

    Hall of Fame

  • Validated Member
  • PipPipPipPipPipPipPip
  • 1,089 posts
  • Gender:Male
  • Location:Redwood City CA
  • Interests:Cartography, wood working, wooden boats, fishing, camping, overland travel, exploring.
  • United States

Thanks for the explanation David.

In our experience this happens after a join operation, where overlapping paths were incorrectly handled, creating a loopback at the joining vertices.
We tried to recreate this on river data that has not been joined, and it didn't happen.

I'll file a feature request for a tool that rectifies this type of data, maybe we'll get to it if there is enough interest.


That would be great and certainly help alleviate some of the hassle associated with moving segmented line work from shapefile into AI.

GIS Reference and Instruction Specialist, Stanford Geospatial Center.

 

www.mapbliss.com

 





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

-->