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Mapping

Show Profile  Michael Posted: 30 May 2014, 4:28 PM  
Thanks. You're relying on matching them up by eye?

Show Profile  Dwayne Posted: 31 May 2014, 10:39 AM  
The tiles I download from Auckland Council GIS website don't overlap and GIMP has an align layers function to snap them together. I used 800% magnification at first (before I discovered the layer alignment function) to move selected layer pixel by pixel which worked as well.

Show Profile  Michael Posted: 5 June 2014, 10:57 AM  
Take a small gap between two buildings that has a garden in it and you don't want people to cross. For argument's sake the garden is 0.6X0.25mm at map scale. A patch of olive green would be very hard to see, and there are minimum sizes of areas of colour. An impassable wall across the gap might just be legible but could look odd because it would be fatter (0.4mm) than it is long. It could also be confusing on the ground to find no wall - am I in the right place? What other solutions?

Show Profile  Martin Posted: 5 June 2014, 11:49 AM  
Try 421 Impassable vegetation, minimum width 0.4mm

Show Profile  Greg Posted: 5 June 2014, 1:07 PM  
or just follow ISSOM

2.1 Map legibility
Map legibility depends on the chosen map scale and a well-chosen set of symbols as well as the
application of generalisation rules. The ideal representation would be realised if every feature could be
represented in true shape. Obviously, this is impossible, and an effort to draw each feature true to scale
would result in a map impossible to read even with the aid of a magnifying glass. Depending on the chosen
map scale, some symbols must represent features and be exaggerated in size, often far beyond the actual
ground limits of the feature represented

and under 3.3 Dimensions of map symbols
All features smaller than the dimensions above must be either exaggerated or omitted, depending on
whether or not they are of significance to the competitor

To me its pretty clear, I wish map makers would actually read the (entire) specifications and understand them, rather than just make their own stuff up.

Show Profile  Bryan Posted: 6 June 2014, 10:28 AM  
Lots of different options: (all are part of ISSOM)
- olive
- impassable vegetation
- temporary out of bounds (purple)

All of these could be made clearer in the field with appropriate taping especially near a control or where
a possible route exists but the planner wants it out of bounds and wants to ensure that competitors don't accidentally or on purpose take that route.

Also, all options can be made clearer through exaggeration making the gap bigger but you run the risk of distorting the building shape so much that it causes more problems than it solves.

ISSOM also mentions for buildings with forbidden access that they may be just represented in a simplified manner and that areas totally contained within a building shall be mapped as being a part of the building - another option is to have just one building with no gap but this may cause
navigation errors when the competitor finds the gap and can't see it on the map.

There are many ways of showing the same thing - depending on the area, some will end up fairer/clearer than others.
I remember in the World Cup two different features in Wellington College (underpass tunnel and split level) each went through more than 15 different versions before the planner, controller, mapper, NZ controller and IOF SEA came up with the final compromised version that they were happy to live with.

Show Profile  Michael Posted: 6 June 2014, 12:18 PM  
Thanks for contributions. I didn't think of 421 as I thought it had an implication of dense vegetation (and re-reading it, I still think so). Didn't think of 714 either which seems to have an implication of "construction".

Regardless of the colour, the difficulty is that we are making a sport out of tiny gaps and obstacles. A patch of full green is going to have to be exaggerated 3X to get near the minimum area of colour, a patch of olive 6X, and there's no minimum area of 50% purple but it would be one of the above.

Show Profile  Jamie Posted: 7 June 2014, 7:18 PM  
yeah impassable vegetation wouldn't be appropriate if it was passable. I would think about exaggerating the gap between buildings and using the olive green (with outlines).

Show Profile  Jason Posted: 8 June 2014, 7:00 PM  
In my experience of sprint events some of the best legs on paper are compromised in the terrain by a technically impassable feature that is impossible to map and mark clearly. Where the mapper can't resolve this the planner's final option is to redesign the course.

Show Profile  Michael Posted: 14 July 2014, 10:03 AM  
Have any Dropbox users met this? Uploaded an OCAD file. Went to use the original again and "cannot open file..." Sidelined the offending file, downloaded, opens OK. Later, signed out of Dropbox; the offending file now opens successfully. Dropbox to blame or is it coincidental?

Show Profile  mcroxford Posted: 14 July 2014, 8:41 PM  
I has a problem with a mystery disappearing file about a month ago that reappeared again. Put an OCAD map in a folder and shared link on the course planning workshop I was running. Everyone accessed it before the training got there opened Dropbox and nothing was there. Got home and behold it was there again.

Show Profile  Michael Posted: 14 July 2014, 11:57 PM  
May indicate deeper problems with Dbox? Any other issues out there? Is it a suitable place to keep a club's master files?

This message was edited by Michael on 14 July 2014, 11:59 PM

Show Profile  Michael Posted: 22 July 2014, 1:22 PM  
There's now elevation data on an 8m grid on the LINZ Data Service, this is twice as fine as the previous best. That's fine horizontally not vertically, it has been compiled from the same source data (the LINZ 20m contours which are now pretty old hat). It may not be much better at finding the holy grail, er, generating contours finer than 20m where you don't have photogrammetry or LIDAR. Anyone used it?

Show Profile  Michael Posted: 3 August 2014, 3:14 PM  
Got some and it works OK in terms of allowing OCAD to calculate contours. Always disappointing when the subtle shapes that we depend on to indicate spurs and valleys get lost in the interpolation processes. (I compared to the digitised 20m contours, which may even have lost something compared to the original topo, would they have been hand plotted?) Perhaps OK to fill in stuff where you don't have anything else, say just outside a council's LIDAR coverage.

Show Profile  Michael Posted: 5 August 2014, 1:54 PM  
Further to above Dropbox issue, it hit me today except in regards to largish background files. An OCAD file that wasn't sent via Dropbox refuses to open because its backgrounds WERE. Furthermore it freezes OCAD and I have to "end process" to get out. All pointing to my Dropbox sign-in as the problem because when I sign out it goes away.



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