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+--- Thread: Digitising tablets (/showthread.php?tid=1512)
Digitising tablets - kevin wooldridge - 16th April 2009
Bob, I dont use a stitching programme because basically they don't work. It may look good but it is never accurate.
My suggestion is (especially if you are using MoL style planning sheets) that you scan each feature by centering it on the scanner. Name each scan after the structure/feature number and give it a gridsquare prefix (i.e 100/200-P23). Load up each individual scan into ArcView, trace the feature, save and move on. The error in such a method is limited to the error inherent in your scanner.
The joy of the single context planning system vis a vis a programme like ArcView is that you only need to georeference one plan in each grid square and then all other plans share the same co-ordinates. The
joy of gridded plan sheets is that you always have a background scale in which to test/measure potential distortion.
With peace and consolation hath dismist, And calm of mind all passion spent...
Digitising tablets - chiz - 16th April 2009
thats pretty much how I was planning on doing it, which is a relief.
Good suggestion re pre-fixing the files so you block calibrate, although that way you have to go back and rename the polygons manually. Can you use a / in filenames in arcView, I was always under the impression you couldn't as it indicates a new folder level? Get around that by separate folders for each 5m square? then 'join' the segments of multi-square plans later? faff either way I suppose.
It is indeed the distortion from the scanner which I've had trouble with in the past. It was quite bad in times, too bad in fact.
Digitising tablets - kevin wooldridge - 16th April 2009
In ArcView I use an extension programme that prompts me to fill in attribute boxes as I draw so you do have to fill in the details manually, but you do it whilst still in that drawing. Can't think of the name of the ArcView extension at the moment, as I only have ArcGIS on this computer. I will check it out on my laptop and let you know tomorrow....It might be Points to Polygons or something similar.
With peace and consolation hath dismist, And calm of mind all passion spent...
Digitising tablets - BAJR Host - 16th April 2009
Anyone fancy putting all this down in text form... would love to make this into a BAJR Guide... very useful discussion that I would hate to lose to the archives...
Kevin knows his stuff! no sausages there!
"Entrepreneurs are simply those who understand that there is little difference between obstacle and opportunity and are able to turn both to their advantage."
Niccolo Machiavelli
Digitising tablets - kevin wooldridge - 16th April 2009
As it happens I only have a first aid course to attend next week so lots of spare time. Leave it with me. I will make a draft based on our discussions to date and then submit it for others to consider and/or add to and/or fill in the gaps....
With peace and consolation hath dismist, And calm of mind all passion spent...