shrug-l: Compressing TIFFs and transforming CAD data

[Tripp Corbin]

Having attended several pre-release demos for 9.2 ESRI touched on the 2 point limit introduced with 9.2. Their logic was that in theory CAD files are normally more accurate at least relative to the features inside the drawing than GIS data. So to maintain the overall integratity of the drawing they do not allow skewing.
 
Tripp Corbin, MCP, CFM, GISP
Associate Vice President, GIS/Mapping
ESRI Authorized Instructor
Keck & Wood, Inc.
www.keckwood.com
(678) 417-4013
(678) 417-8785 fax
 
Keck & Wood, Inc offers instructor led and virtual training for ESRI's ArcGIS & ArcView software.
Please visit www.keckwood.com for more information including a schedule of upcoming classes.

________________________________

From: shrug-l-bounces at lists.dep.state.fl.us on behalf of Kristal Walsh
Sent: Thu 4/26/2007 3:11 PM
To: shrug-l at lists.dep.state.fl.us
Subject: FW: shrug-l: Compressing TIFFs and transforming CAD data



Hi all, thanks for everyone's input and offer of assistance last week on various approaches to referencing a large TIFF file that I was working with.  Here's the sum and a couple other comments on spatial referencing.  Would love to hear from some experienced users on best practices for working with CAD data. 

 

Several folks had suggested ArcScan to get around the size limit, however, at the present time I only had access to ArcView 9.2 with only a demo version of spatial analyst.  Rescanning at this point was not an option.  I tried to clip out aoi from the TIFF but that process was still running after several hours, so I had to try an alternative method.  I finally used the spatial adjustment tool, as Tripp had suggested, to get the CAD files close and then manually digitized/edited the rest also using the georeferenced TIFF as an additional resource.  Here's some issues I had with using the spatial adjustment tool and the georeference tools for CAD files. 

 

I exported the line drawing from the CAD file to a shapefile, then set several displacement links with the tool.  Transform from and to links didn't seem to yield a very good RMS even with >6 GCP and I had fairly good intersections and building corners to work with from a reliable doqq.  After doing a transformation project, I tried to rubber sheet a couple selected areas but got poor results from that attempt.  Is there a trick to this? I have not used this tool before.

 

I found with georeferencing the CAD file, the scale and shift tools don't allow a preview-as-you-go while performing the shift, so it's impossible to see how far you are actually scaling or moving the drawing. I've seen the demonstrations work well but the boundary 'guide box' didn't seem to show up for me.  Anyone know why they restrict 9.2 to 2 gcp  A coworker forwarded this lab to me from the ESRI forum - maybe this is the way to go next time (see attached). Thanks and hope to see everyone at SERUG next week. Kristal

 

Kristal Walsh, GIS Specialist

Baskerville-Donovan, Inc.

449 W. Main Street

Pensacola, Florida 32502

(850) 438-9661, ext. 4354

________________________________

From: Tripp Corbin [mailto:tcorbin at keckwood.com] 
Sent: Tuesday, April 17, 2007 11:42 AM
To: Kristal Walsh; shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Compressing TIFFs

 

Kristal,

Have you tried using ArcScan? I do not think it has a size limit. Other than that you will need to reduce the actual file size and not through compression. Compression only reduces the storage size. The image must decompress into memory when viewed bring it back to it's original size or at least that is the way I understand it. So you would need to reduce your resolution, trim the image or some combination of both.

 

 

Tripp Corbin, MCP, CFM, GISP

Associate Vice President, GIS/Mapping

ESRI Authorized Instructor

Keck & Wood, Inc.

www.keckwood.com <http://www.keckwood.com/> 

(678) 417-4013

(678) 417-8785 fax

 

Keck & Wood, Inc offers instructor led and virtual training for ESRI's ArcGIS & ArcView software.
Please visit www.keckwood.com <http://www.keckwood.com/>  for more information including a schedule of upcoming classes. 

	-----Original Message-----
	From: shrug-l-bounces at lists.dep.state.fl.us [mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Kristal Walsh
	Sent: Tuesday, April 17, 2007 11:42 AM
	To: shrug-l at lists.dep.state.fl.us
	Subject: shrug-l: Compressing TIFFs

	Good morning everybody, I have received a large TIFF of an old scanned map that is approx. 450mb.  I georeferenced it and tried to convert to vector for further clean-up but spatial analyst is giving me an 'over the max 2GB' error.  I tried a lossee compression because I just need the boundaries from the map but this did not help and took over 2 hours to process.  Can anyone give me a suggestion? Thanks! Kristal

	 

	Kristal Walsh, GIS Specialist

	Baskerville-Donovan, Inc.

	449 W. Main Street

	Pensacola, Florida 32502

	(850) 438-9661, ext. 4354

	 

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