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Mapping

Show Profile  addison Posted: 21 April 2006, 7:09 PM  
To be honest I would prefer more detail than less. Let us do the simplification in our own minds.

One thing I really did notice when in Switzerland last year was the overall consistency in mapping. They all abide by the same rules and therefore the overall quality of the events that they run is enhanced. You dont have to worry about travelling to a certain area because it is notorious for bad mapping.

The consistent mapping was a massive help for trying to gain confidence in a new area. By the time we left Europe you could look at a rock and straight away know if it was a large or small boulder, or if it wasnt worth mapping. All I can say is that I wish I could do the same here in NZ. Sure mappers have their own "style" but its time to get off the throne and realise that mapping things your way isnt always best.

Show Profile  Michael Posted: 21 April 2006, 9:26 PM  
Interesting views on styles. But they miss the point that we have an international mapping specification. This lays down symbol sizes for legibility. See the specification, page three. Why is that sentence in bold do you suppose?

Show Profile  Bryan Posted: 24 April 2006, 8:28 AM  
Reading the ISO 2000 specification it is easy to see that the specification is open to interpretation. Which is why we are getting wide ranges of styles of mapping in New Zealand. I feel that mappers from both extreme ends of the spectrum (those that generalise too much and those that map too much detail) should take note
of feedback and subsequently map a little bit differently in the future.

I sometimes put too much detail on a map - a trait I'm reluctant to change much - but I will be more aware of the specifications for the future. I trust and hope that others will do the same.

It is interesting to note that Alex Tarr who was on the committee who made the specifications was also the IOF Controller for WMOC2000 and he actually added small detail missing from the maps but never asked for anything to be removed for clarity.

Here are some relevant sections from ISO2000:

Section 2.4 Generalization and Legibility

Good orienteering terrain contains a large number and a great variety of features. Those which are most essential for the runner in competition must be selected and presented on the orienteering map. To achieve this, in such a way that the map is legible and easy to interpret, cartographic generalization must be employed. There
are two phases of generalization - selective generalization and graphic generalization.

Selective generalization is the decision as to which details and features should be presented on the map. Two important considerations contribute to this decision - the importance of the feature from the runners' point of view and its influence on the legibility of the map. These two considerations will sometimes be incompatible, but the demand for legibility must never be relaxed in order to present an excess of small details and features on the
map. Therefore it will be necessary at the survey stage to adopt minimum sizes for many types of detail. These minimum sizes may vary somewhat from one map to another according to the amount of detail in question.

However, consistency is one of the most important qualities of the orienteering map.

Graphic generalization can greatly affect the clarity of the map. Simplification, displacement and exaggeration are used to this end.

Legibility requires that the size of symbols, line thicknesses and spacing between lines be based on the perception of normal sight in daylight. In devising symbols, all factors except the distance between neighbouring
symbols are considered.

The size of the smallest feature which will appear on the map depends partly on the graphic qualities of the symbol (shape, format and colour) and partly on the position of neighbouring symbols. With immediately neighbouring features, which take up more space on the map than on the ground, it is essential that the correct
relationships between these and other nearby features are also maintained.

Section 3.1 Scale

The scale for an orienteering map is 1:15 000. Terrain that cannot be fieldworked at a scale of 1:7 500 and legibly presented at a scale of 1:15 000, is not suitable for international foot-orienteering.

The scale 1:10 000 is recommended for older age groups (age classes 45 and above) where reading fine lines and small symbols may cause
problems or for (age classes 16 and below) where the capacity of reading complex maps is not fully developed.

Where practical the same dot screens as used at 1:15 000 will give the most legible map and are therefore to be preferred.

For practical reasons a map should not be larger than is necessary for the orienteering competition. Maps larger than A3 should be avoided.

(In Bold) Maps at 1:10 000 must be drawn with lines, line screens and symbol dimensions 50% greater than those
used for 1:15 000 maps.



Show Profile  Michael Posted: 1 May 2006, 1:19 PM  
Enough time has elapsed for me to comment on the nationals mapping. As I said I don't like doing it too soon.

Canaan Downs was undermapped to my eyes. I can understand why - the photogrammetry of the treed areas would have been fairly useless, and all of those holes would have had to be fieldworked in. Not to mention the smaller reentrants and other land features. Adding to that the time to get there, makes a big job. Most mapping takes me between 15 and 50 hours/sq.km, and this would be towards the high end. I would like to see more work put in, but I don't think NZOF has ever felt that mapping was its role. Maybe the World Cup was an exception.

Having said that there were some things that I think were objectively wrong. The absence of the track which ran alongside or just inside the patch of dark green forest. The absence of any symbol for a row of stumps which ran down an open ridge. It took significant time to cross, though I'm not sure how I would show it. The absence of the crop, which should have at least been shown as rough open. I didn't run thru it, but if slow enough (and the specification lists HOW slow) it would have justified green stripes.

Which brings me to green stripes. Roger, I think you have a different interpretation of this from the rest of the world:-)) The green stripes that I encountered were not areas of "undergrowth but otherwise good visibility (brambles, heather, low bushes, and including cut branches)". They were areas where the visibility was reduced in line with the reduced running speed, and should have been mapped with the green shade.

Finally, and this isn't strictly a mapping matter. If Roger was the main mapper, then he shouldn't have been the controller. It's impossible to look objectively at the mapping and courses if you have been involved in making the map. This might be OK at a club event where resources are limited, but not for an A level event. Though perhaps NOC was relying on Graham Teahan as the IOF controller for that independant assessment.

It would be good to have some criticism of the other nationals maps.

Show Profile  jeffg Posted: 2 May 2006, 2:24 PM  
It may be that I'm just used to blue north lines on Auckland sand dune maps but I mistook a north line for a road on The Big Rabbit. On checking the ISOM2000 mapping standards I discovered that black is actually the standard but it can be replaced with blue on maps with few [linear] water features. This would apply to most sand dune maps so I think blue north lines would have been good.

Another small error of mine arose from assuming the north lines were 2.5 cm (250 m) apart on this map but they were further apart(an issue raised by Bryan on the Canaan Downs 1:10000 map). So what do the rules say? "Their spacing on the map should be 33.33mm which represents 500m on the ground at the scale of 1:15 000. For maps with other scales lines placing should be at intervals which represents a round number of meters (e.g. 50 m, 100 m, 250 m, 500 m) and the spacing should be between 20mm and 40mm on the map." Well, the examples suggest that 250m is the appropriate spacing for 1:10000, although one could interpret 300m and 350m as round numbers also.

At least the programme for the long distance event forewarned people that the depressions were undermapped.

Getting a bit risky now as I don't have map or control descriptions in front of me, but what the hell, it's only maptalk: the last control on the relay map. Looking at it on the ground you'd say it would be described as the side of a thicket, with a dark green blob on the map. But it didn't look like this on the map at all, and I suspect that people who heard the announcement that it was THE final control and who memorised its position (and checked the code of course) rather than reading the map had fewer problems than those who actually tried to read their way into it. Only reason I mention this is that there were some fairly high profile difficulties in finding the final control.

But all this stuff is small change and I must say how much I enjoyed all the events and maps.



Show Profile  Martin Posted: 2 May 2006, 2:51 PM  
I also mistook the one of the north lines to be a road in the middle dist, no wonder I never hit it! The finish of the middle was marked on the map as being on a single distinctive tree, infact the finish on the ground was right out in the open, and there were two large distinctive trees not one...

I think it was #2 and #3 on course 2, both were mapped as contour depressions, in reality they were hugely different in size: #2 would have fitted a truck, #3 a mini.

Not a mapping issue, but what was up with the random start times? some 6min, some 3min?

Show Profile  svendp Posted: 3 May 2006, 7:44 PM  
I have some comments regarding the relay map.
A large part of the map was residential area showing streets only and symbol 527 Settlement to fill in the areas between the streets.
We were told at the briefing that any area marked with this colour
was out of bounds and that the symbol was an official IOF out of bounds symbol or something to that effect.

Checking the the ISOM 2000, there is no indication that symbol 527
is an out-of-bounds symbol or forbidden area.

The mapping specification has two - and only two - out of bounds symbols (we are talking standard foot-o maps here, not sprint-o)
and symbol 527 in not one of them.
The symbol was included in the map legend but no mention of it being out of bounds.
If an area is out of bounds, is there any reason why symbol 528 or 709 should not be used? These two symbols are, after all, the only
two shown in the mapping specification as being out of bounds.

The symbol 527 Settlement was used incorrectly by the mapper. The specification reads: "Roads, buildings and other significant features must be shown."
So either the buildings should be shown or the alternative symbol should have been used.

On my relay course I observed several older people struggeling to cross fences and I think it would be a good idea to mark the position of gates with symbol 525. It is generally easier to gross at a gate.

Regarding north lines I think it should be compulsary to use arrowheads. The mapping specification does not make arrowheads a requirement but suggest they may be used, The word "may" have been used too frequently in the mapping specifications and should be replaced with "shall" or "must". Any specification should be exact and precise and not open to interpretation. The ISOM 2000 has failed in thet respect.

Another thing regarding the relays, which has nothing to do with mapping - why is it so difficult to do a control description with the correct symbols?

In spite of all the above I enjoyed all the events and I take the opportunity to thank the Nelson and Marlborough orienteering clubs for a tremendous effort in hosting the 2006 Nationals.

Show Profile  Greg Posted: 3 May 2006, 8:23 PM  
Are the north facing numbers for controls not enough to show you which way is north, when you have you map folded (or scrunched like Neil) it is easier than unfolding and looking for arrows

Show Profile  Neil K Posted: 3 May 2006, 8:26 PM  
9 6 1 1 11 11 8 8

Show Profile  Martin Posted: 3 May 2006, 8:48 PM  
i far prefer the olive green over say the black stripe for out of bounds. face it, on a map like that it'd be much harder to read the course if it was full of black.

the way I see it, we don't need the black OOB to add to the darkness of a map when there's a adequate green symbol that we've been told about and can see easily.

Show Profile  SJ Posted: 3 May 2006, 9:03 PM  
I tend to agree with Martin here, that the green may not be the official standard, but is much clearer and less obtrusive I find.

I would add that I, too, have been caught out in the past by black north lines. I prefer blue, as there is generally not so many water features present on NZ maps that this causes confusion. What's more, water courses rarely run in straight lines, while tracks and roads often do.

Another thing that has been pointed out is control descriptions. I have noticed recently (not only at Nationals, but inluding Nationals) that there has been a bit of an interpretation-required style of doing control descriptions. Perhaps the course setters have not checked the standards, or they are unsure of what is what... But I feel that if runners are expected to know how to interpret all of the IOF descriptions, then surely course setters should be expected to use them correctly.

I find it offputting in a race to have to try and decipher what a control description means, or to see a control description which actually reads something like "knoll, western part" instead of "western foot". In fact, I think there is often incorrect use of the placement of a control with respect to the feature ie. side, part, foot, edge, etc. I would also add that it seems that re-entrant description is often forgotten - upper, middle or lower part, and I have found on several occasions that this ambiguity has lost me 5 or 10 seconds, and a couple of times it has even led me to think I have made a mistake and run off, when in fact the control was just up the re-entrant a bit further. Although 5 or 10 seconds does not seem a lot, it can add up, and when there is a "bingo" component of finding controls it is not very fair.

This message was edited by SJ on 3 May 2006, 10:05 PM

Show Profile  Martin Posted: 3 May 2006, 9:33 PM  
i can think of one of the control at NISS that could have been described much more accurately as reentrant upper part, instead of just reentrant. it was near the top of a damn big hill!

Show Profile  Marquita G Posted: 3 May 2006, 9:47 PM  
As I understand it, the control description "re-entrant" is used when the control is in the middle of the re-entrant. Therefore "re-entrant, middle part" shouldn't be used. "Upper part" or "lower part" are used when the control is placed near to one end or the other. This is especially important when the re-entrant is a very long one and covers several contours. If the re-entrant is a single contour, "upper part" or "lower part" wouldn't be applicable.

Show Profile  SJ Posted: 3 May 2006, 10:37 PM  
Yes, you're right - there is no "middle part". But I disagree that a description is not needed if the re-entrant is a single contour. I can think of many control sites I have visited where a re-entrant covers only one contour, but is long and shallow, 20+ metres. Remember that is still only 2mm on a 1:10000 map, but means a 4-5 second run at least from one end to the other, plus more time stuffing round looking left and right along the re-entrant, and the time can easily add up to 15 seconds each control, and it could quite conceivably happen several times on a course of 15 controls.

This message was edited by SJ on 3 May 2006, 11:37 PM

Show Profile  Michael Posted: 3 May 2006, 11:08 PM  
I intended this to be a mapping topic. Could I ask that other technical topics go on another one?

Svend you're right, the treatment of "settlement" as OOB is "common usage" and not there in black and white. But I understand it is so common in Europe that Carsten disqualified himself from a race when he realised he had run through some, didn't he?


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