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Mapping

Show Profile  Michael Posted: 11 July 2008, 2:59 PM  
I've been working with Linley Earnshaw on a map and we have decided to standardise on the numbering of symbols designed to help drawing and maintenance of the map but hidden on production prints.

I use several of these but have until now just used any old number (eg generated by "duplicate symbol") and this randomness is a pain when copying bits of one map into another. Here's our list. Anyone got any others?

750.0 Construction line
Purple solid line used for miscellaneous purposes, mostly a track/road visible on a photo but not yet verified in the field.

750.1 Miscellaneous contour
Purple dashed line used for stuff that can't be seen on a photo, such as old contour position during extensive changes, contour while looking for anomalies such as loose ends (orphans).

751.0 Vegetation line
Green line used for definite edges of vegetation visible on photos.

751.1 Uncertain vegetation line.
Green dashed line for lines on photos which might be edges of vegetation, or edges in shadow where it is hard to make out the true position.

752.0 GPS track line
Blue dashed line, may have colour variations to distinguish lines on different occasions, eg 752.1

753.0 GPS Waypoint.
A small blue dot. May have colour variations to distinguish readings on different occasions, eg 753.1

754.0 Cartographers Notes
Purple 5pt text used for miscellaneous purposes. General notes off the edge of the map, or specific notes relating to an area eg "?" to indicate fieldwork ambiguity needing revisit. May have size variations for specific purposes, eg 754.1


Show Profile  ole codger Posted: 11 July 2008, 6:14 PM  
We have been mapping the Old Glenora map and we could have done with another rock symbol. There are small and large boulders and big circumference boulders which are drawn. We could have done with a rock pillar type symbol for extra tall boulders that have a similar circumference to large boulders. These can be 5-10m high and stand out visually amongst the other boulders but on the map they are the same as a large 2m symbol . Of course if it is a control site the height can be described but it would be good for the orienteer to recognize them on the map while orienteering. I recall some mappers from the old hand drawn days attempting to draw them differently.

Show Profile  Michael Posted: 12 July 2008, 7:44 PM  
Following the World Masters Orienteering final on 17 October 2009, a two day mapping workshop will be held for Australian and New Zealand mappers on part of the areas used for the Masters qualification and final races. The emphasis will be on changing contours and the convenor will be Eric Andrews.

Source: http://www.nsw.orienteering.asn.au/

Show Profile  Michael Posted: 12 July 2008, 8:29 PM  
I found the above by mistake when I was looking for the OA rock mapping guidelines http://orienteering.asn.au/technical/mapping/mappingstandards/gfolder/opmanpdfs/602mappingrock.pdf

These were a bit ambiguous on Ole Codgers's rock pillar issue, I read that rock pillars were shown to scale, but also that they might need to be exaggerated to make them stand out from "boulders". Alex and Eric would have some recommendations on this, those guidelines are pre-2000.

Show Profile  Michael Posted: 12 July 2008, 8:41 PM  
Reading on to the "boulder" section, I wonder if you just need to adopt a bigger size for a boulder to be called "large". Oz recommends that no more than 10% of boulders be "large". You can use a medium dot for those that are in between.

Show Profile  robbie Posted: 12 July 2008, 10:01 PM  
You can make a symbol. Place it out side the drawn map then duplicate and place in position. I have done this with rock shapes similiar to Michaels knolls.It would also work with rock pillars

Show Profile  Michael Posted: 14 July 2008, 6:10 PM  
From the world champs maps on the web, I suspect they've used the "transparent" option for the purple. I haven't used it but think it has the potential of reducing the need to break circles and lines. Do you think the course stands out though? Wonder what the competitors thought.

http://www.woc2008.cz/files/images/scontent/maps/sprintF/sprintF_MEN.gif

Show Profile  onemanfanclub Posted: 14 July 2008, 9:00 PM  
In the context of a sprint map with lots of big buildings it worked for me sitting down in front of a screen. Not as hard a test as running with it in your hand though. And would it work so well in a more trad orienteering context?

Show Profile  Michael Posted: 9 October 2008, 10:26 PM  
The LINZ website says "Orthophotos are no longer commissioned by LINZ so no further images will be added to this collection." So we'll have to pay aerial photo companies where we want later coverage or areas that LINZ never got round to. Those who have done this might list here the companies and indicative costs.

Show Profile  Bryan Posted: 10 October 2008, 8:09 AM  
I've not used orthophotos very much - they usually were too expensive to pay for (because the aerial photos have been rectified and are registered to a map grid).

I have access to New Zealand Map Grid images over the whole country via my company, Terralink.

Other sources are: local councils, New Zealand Aerial Mapping, Google Earth, Microsoft Virtual Earth.

Quite often these days I don't order photogrammetry - I just interpolate contours from the LINZ 20m contours, overlay aerial photos in OCAD - just use the normal registration method in OCAD - this is fine for Orienteering areas which are only a few square kms. Recently I created a 5m base map and had a choice of Terralink images and Google images. I choose the Google images as Google drapes a 20m 3D terrain model over them and when interpolating you can pick out the gullies and ridges better.

Show Profile  Svend Posted: 10 October 2008, 8:14 AM  
All local authorities in NZ has access (licence) to high resolution
photos from the Quick Bird Satellite. The latest photos I got were only six months old. Because our club is an non-profit organisation
there was no cost involved.

Show Profile  Michael Posted: 10 October 2008, 8:39 AM  
IMO Google is not a replacement for orthophotos. They seem to be stitched together in a quick and dirty way, and there's definitely height distortion.

Show Profile  Selwyn Posted: 10 October 2008, 9:45 AM  
You are lucky Svend. The 5 councils in Auckland Region have varying policies re sale or supply of Photo data. Outside of Auckland city it seems the local body can supply small "tiles" (about 2 or 3 standard suburban street blocks)free if they wish, and some do. Bigger areas for the whole region must be purchased through Auckland City Council who hold the licensne and selling rights for the region. They have given a 50% discount.
I have found google photos to have distortion in some areas and the tree shadows are usually enormous compared to good summer orthophoto.


Show Profile  Selwyn Posted: 10 October 2008, 9:56 AM  
Re: Polyseter drafting film: It seems to be impossible to source single matt polyester drafting film in NZ any more. Does anyone have a supplier. If not, I have done some research and am prepared to import a roll and/or 1000 A4 sheets from England and on-sell o mappers at cost + local postage. Price would work out about 80c per A4 size, including freight from England, which is about 30-40% of the cost.
I have used double matt film for many years but I'm trying to get better visibilty of orthophotos through the film and I'm hoping single matt will perform better.
The English company sent me 2 sheets of sample of 50 micron film. It is rather flimsy and can crease easily which impacts negatively on clarity. So I would most likely order 70 micron thickness.
I also thought the improvement in clarity between double matt and single matt was marginal, maybe 20% clearer. In the past I haven't used the technique of wetting the underside of the film which enhances clarity a lot. I could do this if a I printed my base map on waterproof paper - but not sure if the waterproof paper holds it size when damp.
So, any comments on above. Who would purchase any film if I import?
Comments re 50 micron v. 70 micron.




Show Profile  Paul I Posted: 10 October 2008, 11:34 AM  
I sourced my last lot from Aarque Graphics in Auckland. Since I often overlay the film directly on aerial photos I found single sided matt almost essential to see through (I think it was 100gsm). At the time I think they had to hunt around a bit to get what I needed so I purchased 25 A1 sheets, 1/2 of which have now been used.


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