Errors in Discovery series maps (2005?)

johngalway

Hi folks,

We've noticed on number 38 1:50,000 there are quite a few errors, as in missing streams, missing contour lines, tracks not included. We've checked older versions of the same map, 1995 I think, and these features were included. Bit disappointing when you shell out 22 Euro for the laminated version, and pretty dodgy I'd think navigating in dark or fog! Anyone else find the same?

ATB,

John

Cookie_Monster

there are plenty of track that are or never will be included for whatever reason.

missing contours are not that big a deal, missing rivers would be an issue but not streams. at that scale there's only so much that can be fitted, they may have taken the decision that certain areas were too cluttered to read easily and removed some unimportant features

Alun

Tracks: always a bit hit and miss on OS maps IME. In open countryside, they're not very reliable, some tracks that are shown on the map don't exist at all on the ground, but conversely (esp. in well walked areas) most commonly used tracks on the ground just aren't marked at all. Forest tracks on Coillte property are a bit more reliable, but are subject to change as forest areas are felled / replanted. Farm tracks for example, are a bit hit and miss too ... maybe some of them had been deliberately removed upon request by the landowner to discourage walkers using them? I can't really think of any other reason why something like that would disappear from one edition to another.

Streams: Usually reasonably reliable, however given the nature of upland streams, they can only be completely relied upon for navigation purposes when they're reasonably wide, i.e. lower down away from the source as marked on the map, where they're often virtually invisible either due to being largely underground or dried out in summer. Again though, I can't really think of any other reason why something like that would disappear from one edition to another. There were a few examples on a recent upgrade to sheet 56 where a stream was 'promoted' to being a river and therefore got a slightly thicker blue line as a result, but I've not heard of one being removed completely.

The contours thing intrigues me though. When you say there are missing contour lines, what do you mean exactly? Any chance of two side by side examples? I know that on the UK OS maps they often (deliberately) miss out the minor (10m) contour lines on very steep ground, since not doing so results in a bit of a mess, but I didn't think they did this on the Irish maps.

The only other thing I can think of is that the newer map is based on a newer, more accurate, survey and as a result the contour lines have shifted slightly in the area you were looking at. This kind of thing is particularly noticeable on shallow, flat summit areas, where for example in a previous survey, the summit just about managed to poke above a contour line boundary, but on the newer survey it comes in just below it, so a small contour ring near the summit disappears. In certain cases (but again not on OSI maps) the map makers will add a dashed 'auxiliary' contour line to indicate this fact and to aid navigation.

johngalway

I don't have access to a 1995 map, someone else had one and we were comparing mine with his.

There's a spot height of 192 at M 070 560. There's a track marked on the map running through that spot height. We couldn't find it, there was 6 of us, plus another group of 6 who also couldn't find any trace of it.

There are missing contours on top of Benlevy on my map compared to the 1995 map. It is flat-ish up there but I think the 1995 is more accurate, having been up there.

There was also a stream coming out of a lake, which was marked on the 1995 maps, but not on mine, 2005, but which was still very much there. I can't remember where that one was.

Like I say, my concern is if you're on the hills and the fog comes down, or night falls, or you get delayed, the your visibility is greatly reduced so you're navigating needs to be spot on. If you cross a stream that's not on your map, but may be on the 1995 map, you may question where you are.