The story was first penned in The Manawatu Standard, and it’s since been picked up by Morning Report on National Radio (streaming available in your choice of [Windows Media Player], [MP3] or [Ogg Vorbis] depending on your preference).

I don’t know what the errors are, and perhaps they’re especially bad. On the other hand, I wonder if the fact that the Topo50 series maps have errors means that they’re any worse than the 260 series. It’s hard to tell for sure without more information. It’s in everyone’s interests to have maps that are correct, but it’s common for NZ topo maps to have errors here and there, and sometimes it’s just necessary to accept this. The only way to really be sure about a region, short of asking someone trustworthy or going out with them, is to be prepared for anything, look at the landscape, be in a frame of mind to change plans if necessary and then learn about an area from experience.

I vaguely remember something from a while back (but can’t find a reference) in preparing Topo50, whereby LINZ was convinced to include older tracks and emergency routes that had been removed from some of the more recent 260 series maps. Prior to that there had been discussions about removing even more tracks from the map, but there was an outcry to the best of my recollection. We discussed this in our tramping triangle at work today, and someone suggested that perhaps the false or missing tracks are old tracks that were shown on older maps of the region, and have since been put back in the new Topo50 series.

The strength of topo maps (at least in New Zealand) has never really been about tracks, it’s terrain and topography. Keeping track of tracks and routes is a difficult thing to do, because they’re often difficult to see from the air, especially under trees. They change frequently, often without any official influence. People will sometimes go out expecting to find a good track or poled route based on a map, and find something quite different, but this isn’t something unusual with earlier maps and I’m not sure why it should be different with Topo50 maps. If you happen to go out expecting to find a track, but there isn’t a track, then clearly the map’s wrong. All it does it change the rules a little. it may make sense to continue depending on things like circumstances, experience, conditions and knowledge of the rest of the environment. If you happen to be not terribly confident with continuing, though, the obvious thing to do is something different. In other words, do what it takes to get back into whatever your comfort zone happens to be.

This may mean returning to where there was a track, and going back the way you came to return another day, or stopping and finding a safe place to camp for the night (unless you’re a victim of The Hut Fallacy) to consider things properly with a clear head in the morning. I guess this whole philosophy implies some kind of good judgement, which isn’t always present and not because people are irresponsible. Sometimes people just have bad days, or groups make strange decisions that individuals might never make alone. I don’t know exactly what to do about this because there have forever been people getting into trouble for these reasons and most likely there will be in the future, irrespective of improvements to track details on maps.

Some good news with the switch to Topo50 is that changes and updates are likely to get into the mapping system much more rapidly. With its overhaul of mapping systems, LINZ also completely changed the way it publishes maps. Pre-processing is now all done in-house, such that LINZ can now run off a new map edition soon after updating their system. It won’t take existing maps with errors off the shelves, but it could mean that new orders from retailers sent to replace them have corrections. Previously, new editions only came out every decade or so, and each map had to be manually re-plotted and carefully examined (which is why some maps had inconsistent shadings), and was probably pre-printed in large numbers.

Hopefully the ability to correct maps more quickly will also lead to more people submitting corrections. There are enough people out tramping with good GPS devices these days that getting accurate positions of the tracks is becoming much easier, as long as you can trust the person providing the data, and trusting the data may be the most difficult part. For instance, I’m now trying to digitally track every time I go out for a walk, but just because my GPS has been somewhere doesn’t mean it’s a track. My GPS stops and starts, it takes short-cuts, it ventures off-track to look at interesting things, and sometimes it just leaves the track completely because there is no formed track to wherever my GPS wants to go. When I return, I don’t always have a reliable memory of exactly when I was and wasn’t on a track, or the standard of that track, but then that’s not my main motivation for digitally recording where I’ve been. I guess time will tell.

A couple of weeks ago, I took part in a bulk order of the new Topo50 maps, which replace the old 260 series that’s been in publication for several decades until now. I’m now the owner of 18 Topo50 maps to get me started, having picked up most of them for $3.50 each, around half the usual retail price. You can get this price (which includes GST but not postage) if you have a bulk order or 20 or more maps direct from LINZ, which makes it useful for clubs or groups of friends who know in advance what they want. I wrote about these maps last year, including more detail about why it’s actually happening and what the main changes are. The new maps have a couple of obvious differences:

• They’re smaller. All maps are now metric A1 size. This means they fit less information, but they should also fit more nicely into other equipment that takes metric paper sizes such as photocopiers and satchels. Smaller maps also means less to carry, unless you happen to be crossing map boundaries (which is more likely). Another side effect is that the boundaries between maps have shifted all over the place. Some areas fit more nicely into the Topo50 map boundaries, whereas others definitely don’t.
• The map grid has changed, which means all reference coordinates have changed. This is the most important reason why LINZ wants people to start using new maps, so as to reduce confusion between the old and new map grids.

Strictly speaking it’s no longer necessary to buy the maps at all. LINZ now makes them downloadable, letting people with adequate facilities print their own and mix and match the parts they want. Personally I still prefer to go with the standard pre-printed maps, mostly because I trust the consistency of production, with an idea of how the paper and toner will last, knowing that every map will have coordinates properly produced, and so on.

I possibly haven’t broken these regions into the same segments that everyone else would have, but a few notes about the various regions are:

Wellington Old maps: R27, R28 & Pt. Q27 (Wellington), R26 & Pt. R25 (Paraparaumu). New maps: BQ31 (Wellington), BQ32 (Lower Hutt), BP32 (Paraparaumu) for the northern-most part.

In the 260 series, the bulk of the Wellington region used to exist on a single map titled “R27, R28 & Pt. Q27“, of which R27 was the main component and the other two parts were tacked on to two different edges making it an unusually large 260 map. Further north up to Waikanae, including Kapiti Island was on another spliced-together map. These inconsistent sizes splattered around the system were one of the things making the 260 series more expensive to produce. The Wellington map contained all of Te Kopohau Reserve, Makara and the coast up to Porirua, all of Belmont Regional Park, everything around the Hutt Valley and the bulk of the Orongorongos and Rimutaka Range as far as the south coast, with a tiny part of the southern Wairarapa on the edge (really only Lake Oneke). The northern map (which I’ve rarely used) contained Kapiti Island, most of the Akatarawas, and a slight fringe of the Tararuas east of the Akatarawa Road between Upper Hutt and Waikanae.

In the Topo50 series, the same region now crosses three main maps. Map BQ31 (Wellington) covers all of Wellington out to the Cook Straight on the south and west, but only extends north to about Tawa (not as far as Porirua) and east-wards doesn’t quite reach Petone. Pencarrow Head juts into the eastern edge of the map, but apart from this none of the Eastbourne side of Wellington Harbour reaches this map. All of Lower Hutt and the bulk of the Orongorongos and Rimutaka Range is drawn on map BQ32 (Lower Hutt), although without as much to the north. The eastern edge of this map is roughly the same as the old 260 Wellington map, just reaching Lake Oneke. Everything north of Tawa, and still reaching about the same fringe of the Tararuas, is now on BP32 (Paraparaumu). Most of Kapiti Island appears on this map, but the north end with Waiorua Bay is chopped off. If you specifically care about the north end of Kapiti Island, it’s worth noting that Topo50 map BN32ptBP32 has been intentionally shifted south to overlap, and includes all of Kapiti Island. (I don’t own this map.)

Tararuas Old maps: S26 (Carterton) for the southern end, S25 (Levin) for the northern end. New maps: BP33 (Featherston), BP34 (Masterton), BN33 (Levin), BN34 (Shannon).

I think the Tararuas lost out with the new map divisions. In the 260 series nearly the entire range was nicely covered by two maps, but now there’s a mixture of mountain range, flat farms and populated towns and coastal areas. I was going to take my new maps into the Tararuas last weekend, but took the old ones instead when I realised our stint on the middle part of the main range was going to cross three different maps. The route just fitted the old maps so much more nicely.

All of the Southern Crossing region fits into BP33 (Featherston), which also seems to be the most filled-up of these maps as far as tramping regions go. It also includes the Southern Main Range right up to Anderson, and (nearly) all of the route down to Waitewaewae Hut. The map extends north to Otaki Forks and Waitewaewae Hut, about the same line as the old map. It’s the east-west split where things get annoying, as the Featherston map only extends as far east as Mt Holdsworth and much of the Totara Creek track. If you want a map that includes places like Holdsworth Lodge, Mountain House and Powell Hut, you’ll also need to get map BP34 (Masterton), which is mostly farm-land but includes this corner of the Tararuas and also the Barra Track up to Mitre Flats (but not Mitre). That whole area falls into a frustrating network of map boundaries. If you wanted to head further north to somewhere like Cow Creek, or up over Three Kings or Mitre on the tops, you’d find yourself getting onto yet another map, BN34 (Shannon).

Much of the northern end of the Tararuas falls on map BN34 (Shannon). The souther end of this map falls a little further south than the Kiriwhakapapa Shelter and North King. The Shannon map includes pretty much all of the Northern Main Range, north-west of Arete and past Dundas, down past Herepai Hut or onward into the leatherwood-laden hell-hole towards the Mangahao Dams. West of Arete, it’s necessary to switch to map BN33 (Levin), which includes most of Carkeek and Dorset Ridges on the far east, most of the middle Main Range, and Oriwa Ridge.

Ruahines Old maps: T23 (Kimbolton), U23 (Dannevirke), T22 (Mangaweka), U22 (Ongaonga), U21 (Kereru). New maps: BL36 (Norsewood), BK36 (Taoroa Junction), BK37 (Tikokino).

I haven’t really visited enough of the Ruahines to know where all the best bits are, but at face value I think the area’s done much better for map boundaries in Topo50 than it did in the 260 series. The Ruahines are long and thin (especially at the southern end), and trend diagonally up the North Island, at least compared with the map sheet indeces. In the 260 series, the range crossed at least 5 maps, possibly more, but often only cutting corners or scraping edges of the maps. For instance, the walk into Heritage Lodge or Rangiwahia Hut occurs on the far east of map T22 (Mangaweka) — a map which is almost entirely farmland irrelevant to the range. Further east, the bulk of the Ruahine Range at that latitude falls onto U22 (Ongaonga), but still only uses 1/3 of the map surface. Further south, most of the range fell diagonally across T23 (Kimbolton), but just cuts the corner of U23 (Dannevirke), and that could have been annoying for anyone wanting to walk across to any of the 6 huts marked on that tiny corner of the Dannevirke map. Towards the northern end, map U21 (Kereru) was actually reasonably full of Ruahine Range area.

The reason I think the Ruahines win so much under Topo50 is because the west and east map boundaries are placed to fit the full width of the range so much more nicely than in the old maps. About the same area for which I needed 5 large maps with lots of farmland is now covered by 3 smaller maps of mostly mountain range. The thinner parts of the range around Rangiwahia, Heritage and further south now have the entire width of the range falling within a single map — in this case BL36 (Norsewood). The two maps further north and north-east, BK36 (Taoroa Junction) and BK37 (Tikokino) cover the whole area up the Ruahine Main Range, and out to the edges on both sides without huge amounts of extra.

Aorangis Old map: S28 (Palliser). New maps: BQ33 (Lake Wairarapa), BR33 (Ngawi).

The Aorangi Range, mostly a hunter’s playground on the south-east coast of the North Island, used to be entirely on one map. I guess there’s a slight loss here because it’s now mostly on two. The southern border of map BQ33 falls just south of the Putangirua Pinnacles, which is a starting point for a trip I’ve now done twice, to walk south from there out to Cape Palliser. Both maps have a lot of wasted space outside the mountain range, but at least the whole range does seem to be covered on just two maps, though, and it doesn’t get more complex.

Mt Taranaki / Egmont Old maps: P20 (Egmont), plus a few extras around the edges. New maps: BJ29 (Mount Taranaki or Mount Egmont), BH29 (New Plymouth).

Most of Mt Taranaki/Egmont used to fit on P20 (Egmont), with the exception of a couple of edges of the national park falling onto P19 (New Plymouth) or Q20 (Stratford). The design of Egmont National Park, I think, means that those two edge maps often wouldn’t have been relevant anyway, simply because they mostly involve just the beginning of well define tracks up to the mountain in the middle, and also because the Park has several roads leading up to the inner section in which many people start their activities regardless. Consequently it was often possible to get by in all of Egmont with a single map.

In the Topo50 maps, I think the boundaries become slightly less efficient. There is still a single map, BJ29 (Mount Taranaki or Mount Egmont) that covers the central cone of the mountain. Most of the national park is restricted to the north-west corner of this map, however, and the entirety of the Pouakai Range to the north east has been cut off. To get the park in its entirety, it’d be necessary to obtain three more maps: BJ28 (Opunake), BH29 (New Plymouth) and possibly BH28 (Oakura). I don’t own any of these, but might get them in the next bulk order I take part in.

I have a few other maps scattered around, but this covers the main Wellington-based regions I tend to spend most time tramping in. If you’d like a look at the boundaries for yourself without leaving the internet, LINZ has published map sheet guides for the new map series, including comparisons between where the old sheets and new sheets lie. My current favourite way to check out the Topo50 map extents online, however, is to visit Koordinates.com and search for “Topo50″, switch on the Topo50 map layer, zoom around to find what I want, then toggle the Topo50 sheet index layer to see which map it’s on.

LINZ has a large section of their website which describes the project in detail, explaining how it will affect people’s use of maps, GPS devices and other related systems. It’s good to see this actually happening — we’ve been hearing about it for several years now.

Everything you need to know is behind the link above, but I thought I might try to summarise the changes, perhaps to help people understand it better but as much to help myself to get a grasp on what’s changing and why. I’m doing my best to get this as correct as I can, but please keep in mind that I’m an amateur at this. If you notice inaccuracies or omissions, I’d appreciate it if you could point them out by posting a comment. If necessary, I’ll correct the post and credit as appropriate. Meanwhile if you’re keen to get more authoritative information from the source, a good place to start is the LINZ Publications & Other Resources page. The downloadable Topo50 map Reading Guide and the Where in the World Are We? booklets are especially helpful, and much of what I’ve written here is really just a dumbed down version of them.

For a long time now, LINZ has produced both the NZMS260 and NZMS262 series’ of maps, the former of which is used extensively for tramping. These maps are about as official as it’s possible to get for topographic maps of New Zealand. It’s taken decades to produce the entire series, with each map having been manually drawn. As the series of maps has been produced over such a long time, some maps don’t even match properly with neighbouring maps in properties such as colouring, especially if the maps were produced at different times. A few years ago, LINZ announced that as a major project, the map system would be changing and the various coordinate systems associated with New Zealand mapping would change with it.

There are a variety of reasons why it makes sense for LINZ to update the mapping system, but the most important is to make it work more nicely with the alternative “Geodetic Datum” that LINZ decided to adopt a few years ago. To understand why on earth this was necessary at all, let alone what a “Geodetic Datum” actually is and why LINZ cares about it, it’s necessary to understand something about how maps work and how they’re put together.

It’s all about projections

If you’ve dealt with maps before, you’ve probably heard something about map projections. A “projection” is the necessarily imperfect answer to the problem of how to represent the curved surface on a flat piece of paper.

Each of the maps in the NZMS260 series, the NZMS262 series, and probably most other series’ that LINZ publishes, is drawn on a flat sheet of paper, but the land that it represents isn’t flat. What it comes down to is that a flat map is not a perfect representation of the land it represents, and it can’t be. If every map in the series were laid side by side, the combined land area would look very skewed, and if the maps were pushed around to make the land appear closer to the correct shape, they would no longer line up properly side by side, and all of the nice, parallel lines of the overlaid map grid would no longer be parallel. In practice, the Earth is so large that the area represented by a single map is almost flat, and for most common uses (such as trampers taking compass bearings), it’s easily good enough for the job.

This is what a projection is. To ensure that the map can be displayed most usefully in a flat context, LINZ has to skew the shape of the entire country both so it’s not quite correct, and so it’s as un-obvious as possible that it’s not quite correct.

Points of reference and coordinates

Until recently, I’d intuitively assumed that things like latitude and longitude were very easy concepts. ie. With a specific coordinate, just draw a line from the centre of the Earth in whatever direction some brilliant maths indicates, and the geographic point for a given latitude and longitude will be where that line intersects the Earth’s surface. The intuition falls apart once it’s realise that to do this, just for starters, some way is needed for deciding where the centre of the Earth is. It falls apart even further when it’s realised that the Earth isn’t a perfect sphere, or even a sphere with mountains and valleys messing up the surface. It’s actually an oblique spheroid, which means it’s a flattened sphere that’s much wider in the middle than at the poles. The simplicity of projecting lines from the centre is getting less simple all the time.

You don’t necessarily need to know the centre of the Earth to draw a decent map that’s a good representation of an area, but you need reliable points of reference for which you do know the latitudes and longitudes already. The reference points can’t move, because if they do then it means you can no longer be certain about every measurement you’ve taken from them. New Zealand is a geologically active place, where the land moves around, and this is essentially the problem with the old NZGD1949 Geodetic Datum on which the existing LINZ topo maps have been based until now.

Geodetic datums define the reference system

This is where we come back to geodetic datums, because a datum is essentially the reference system on which everything is based. It might be something derived from the centre of the Earth, or it might be something else. It’s essential that it’s reliable and well understood, however, or everything derived from it becomes confused.

NZGD1949 is what’s known as a “local horizontal datum”, and also a “static datum”. It’s a reference system based on the known positions of trig stations around New Zealand that have been measured very accurately, and it also assumes that they never move. This isn’t exactly true, and the way the datum works makes it more difficult for surveyors to model geological movement without a lot of effort. Therefore this kind of system is not sufficient for use in New Zealand for some of today’s needs, because it’s not a reliable reference to the level of accuracy those needs require. Another issue with NZGD1949 is that having been designed to only fit New Zealand’s land-shape and nothing else, it’s not naturally compatible with much of the globally-aware navigation technology available today, notably GPS systems. To work with NZGD1949 and systems based upon it such as the New Zealand Map Grid, such technology has to incorporate lots of conversions. Through doing so, they waste resources and lose accuracy.

NZGD2000, the new Geodetic Datum which LINZ internally adopted in 1998 (but didn’t immediately use publicly in place of the NZMS260 or NZMS262 series’ of maps), is known as a “geocentric three dimensional datum”, and a “semi-dynamic datum”. It’s a referencing system based on a particular definition of the centre of the Earth and it’s been designed from knowledge that takes the whole planet into account. It’s designed around a model that estimates the shape of the entire Earth well beyond just New Zealand. Obviously the use of NZGD2000 doesn’t prevent New Zealand’s land-mass from morphing by about 5 cm relative to itself each year, but through its design it does help the surveyors and geographers at LINZ keep track of what’s actually moving around in New Zealand much more accurately. Otherwise it’s like trying to measure a distance while someone’s pulling the carpet out from underneath you. Also, being a globally-defined datum, it’s much more easily compatible with the GPS network, which operates in that context.

Collateral damage to coordinate systems

Being naive about the topic as I am, it hadn’t occurred to me until I learned of these changes is that latitudes and longitudes, which I’d always assumed were absolute everywhere, are really only subjective to the system used to plot them and that the systems vary in different places. When LINZ switches its maps to use NZGD2000, all places in New Zealand will be assigned a new latitude and longitude, as far as the predominant series of maps are concerned. Effectively, if you were to go to a specific position of latitude and longitude according to an old map and then again according to a new map, it will be as if New Zealand has shifted about 190 metres north and 10 metres east. (Check out the Differences section of the LINZ FAQ for more information about this.) What’s really happening, of course, is that those latitude and longitude lines are slightly offset from where they used to be because New Zealand is properly aligning itself with the same reference point used by much of the rest of the world.

The New Zealand Map Grid (NZMG) will also disappear, to be replaced by a new grid called the New Zealand Transverse Mercator projection (NZTM2000). This happens for the same reason, because the old NZMG was projected onto New Zealand using systems derived from the old NZGD1949 reference system. With NZTM2000, drawing the old map grid doesn’t quite work any more.

Even though LINZ has been doing its surveying using the new NZTM2000 for more than a decade now, it’s certainly possible to hack together maps with the old grids on them and use the old numbers and draw the old lines. In fact, this is what’s been happening over the past decade. During all this time LINZ has still released newly surveyed editions of their NZMS260 and NZMS262 topo maps with all the internally surveyed new coordinates converted back to the old coordinates for publication. This has been so that the new maps would be compatible with those already in circulation, giving LINZ more time to prepare for the change-over which is now here. Ultimately though, this is inefficient and leads to more and more complications and maintenance problems. Sooner or later, it all has to change.

Change happens on 29th 23rd September 2009

On 29th September 2009 (edit: 23rd September 2009), LINZ will finally release its new series of maps into shops. The old NZMS260 and NZMS262 series’ of maps are no longer being produced, and they’ll be completely withdrawn on that date. At the same time, the complete series of all Topo50 and Topo250 maps will be released, and LINZ is taking the opportunity to make several additional changes to the production system of its maps. Notably,

• The standard printed size of map sheets will become smaller and more consistent. In the NZMS260 and NZMS262 series’, maps were printed on a non-standard, and very large, sized sheet. Some maps were even sized inconsistently with their neighbouring maps, especially if a small segment of land existed off to the side, and making an existing map slightly wider would remove the need to print a new map of mostly water. With the new Topo50 and Topo250 map series’, all map sheets will be produced as metric A1 size. In cases where a map will only have tiny amount of land to be nearly useless for land navigation, LINZ will overlap the maps with neighbouring maps to ensure that every map displays a useful amount of land. Therefore some land may be duplicated on multiple maps, but will also do away with maps that are 95% water.
• Maps will be cheaper. LINZ really wants to encourage people to switch to the new Topo50 and Topo250 maps as soon as possible. Part of this encouragement is to make them available to anyone at the wholesale price of $3.50, as long as 20 or more maps are purchased. (ie. A minimum of $70 spent.) This means you could potentially replace your entire map collection relatively cheaply, or alternatively you could put together an order with several friends. LINZ is switching away from sub-contracting the printing of maps, and will now print them in-house, and this is contributing towards the cheaper costs (as I understand it, at least).

  To help people figure out which maps they might need, LINZ has provided material that compares the NZMS260 and Topo50 Map series’, including diagrams showing how grids of the map sheets overlap each other. If you have a collection of NZMS260 maps and need to know which Topo50 maps to buy for the same areas, it’s a good place to start.

The Topo50 maps are already accessible, in a sense. The complete database from which they’re produced is available using NZTopoOnline, part of the LINZ website which can be used to generate and print maps of sections of New Zealand on the fly. Presently the maps from NZTopoOnline don’t come out quite the same, however, because it’s an automated system that only has raw mapping data to generate from. Apart from having been printed professionally and with predictable consistency, printed LINZ maps, once available, will all be rendered more nicely as a consequence of people having gone through the data to ensure it looks readable, notably by doing things such as ensuring labels of features don’t overlap each other, and that kind of thing. With the natural move towards a more digital and centralised storage of all the information, however, it may become much more feasible in the future to print maps on demand, or have agents do so on LINZ’s behalf rather than require retailers to stock hundreds of different maps just in case someone might walk in wanting one. This is more towards the future, however.

Consequences for old maps

Obviously the old NZMS260 maps will still work, and it’s not as if geography changes simply because the New Zealand government decides to draw a new set of lines over it. There’s an underlying theme of encouraging people to stop using their old NZMG maps, but it might take a while for them to disappear completely. I certainly won’t throw out my maps simply because they’re old, and I doubt many of my friends will. Old maps are a great source of information about things like old tracks and routes that are no longer officially marked. Some people have lots of lines and marked up information drawn over their existing maps which is great for reference material when visiting somewhere, and that won’t be thrown out quickly. What I expect to do, however, is to move towards the Topo50 series of maps and take them out tramping with me.

The real problems will occur when communicating information about maps using two different systems, however. For instance, the potential of confusion if someone gives an NZMG grid reference from a 260 series map, which another person tries to apply to the NZTM2000 grid of a Topo250 map. New Zealand’s Land Search and Rescue is taking this seriously, and at the change-over date, all of SAR will immediately switch to the new mapping system in an attempt to avoid confusion when communicating between each other.

The confusion between the two map grids has been of particular concern, and a decision made to reduce confusion has been to design the new NZTM2000 grid so that the New Zealand land mass which it describes does not even overlap the same land mass in the NZMG when the reference numbers are the same. In other words, a grid reference in either system for anywhere in New Zealand will appear as if it’s pointing to open sea if it’s applied back to the wrong system.

Now it’s just a case of waiting

Hopefully this is a reasonable summary of not just what’s changing, but why it’s changing. The “what” part is easy, but having written this up I now feel as if I’m getting a better grasp on what the reasons and problems are. As I wrote earlier, I’d appreciate feedback and corrections, and whatever further thoughts or comments anyone might have on this.

I guess the most important thing to keep in mind is that it’s coming very soon. It seems like a very significant and important change in the use of maps in New Zealand, yet to date I haven’t seen much publicity of it outside tramping circles. I’ve wondered if there may be large clusters of people whom it might affect, who aren’t even aware that the entire mapping system is about to change.