Author Topic: A 1:25k vernier romer  (Read 4169 times)

captain paranoia

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A 1:25k vernier romer
« on: May 29, 2012, 06:25:30 PM »
Twelve years ago, in some boredom, I decided to log the positions of all the archaeological features on the OS Purbeck leisure map.  I used a ruler to measure 8-figure grid references, and it was tedious, but I stuck to it...

Thinking about the problem, I was reminded of vernier scales, and wondered if I could make a 2D vernier.  A little bit of thinking, and some PostScript programming later, and I had a working design.  As with many of my designs, I did nothing with it for years, until I entered it into Alpkit's CoLab08 design competition.  It didn't make the final.  My entry for the 2009 competition won first prize, though...

I thought micronavigators might be interested in the idea.  You can find a description of how it works at Alpkit's website, and the PostScript on an OutdoorsMagic thread.  It allows you to read an 8-figure grid ref from a 1:25k map with relative ease.

http://www.alpkit.com/colab08/entry/4-figure-vernier-romer/
http://www.outdoorsmagic.com/forum/forummessages/mps/UTN/5082

I've since incorporated it into a Portland Plotter to give a combined grid ref and bearing tool.

It's free for non-commercial reproduction (print it on transparency in a laser printer).

Have fun.

Skills4Survival

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Re: A 1:25k vernier romer
« Reply #1 on: May 29, 2012, 09:51:57 PM »
Captain P.,

Interested in all ideas, what is the point of doing this (not meaning to be blunt here !), is it the easy of use, or does it bring additional functionality, or both, or something else.
You talk about a problem in your intro, what do you mean with problem?

Ivo
Ivo

captain paranoia

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Re: A 1:25k vernier romer
« Reply #2 on: May 30, 2012, 12:33:47 PM »
The point is that a conventional, square-grid romer only allows you to measure to three figures in each axis (i.e. it measures 1/10 of a grid square, or 100m).  To get the fourth figure (1/100 grid, 10m), you have to estimate the gap within the 1/10 grid lines.

The vernier romer removes the need to estimate, and allows you to measure, accurately, the fourth figure.  It works in exactly the same way as a vernier micrometer, or any other vernier scale.

The original problem was trying to accurately measure to four-figure ordinates using a millimetre-scaled ruler in each axis, and then convert the reading to the 2-figure, 10m value within a 1km grid square (i.e. divide mm reading by 4).  This gets very tedious when you have a lot of points to plot...

Lyle Brotherton

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Re: A 1:25k vernier romer
« Reply #3 on: May 31, 2012, 12:25:38 PM »
What a great posting and such a neat idea :)

“Opinion is the medium between knowledge and ignorance” - Plato

captain paranoia

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Re: A 1:25k vernier romer
« Reply #4 on: May 31, 2012, 06:31:13 PM »
Is it actually a useful idea for navigation, though?  I've never been sure, as it's rare that I need to specify a grid ref for actually navigating, and even more rarely to generate an 8-fig grid ref.  The only time I really use grid refs is in making a route plan, and, in reality, I rarely use those...  I don't navigate by grid ref; I navigate by associating the map with the real world around me.

Which brings us to the question: what are grid references useful for?

Grid references are only really useful if you're trying to exchange a position on a map with someone else.  Or with something else (e.g. a mapping tool, or a GPS).

With the advent of computer mapping and route-planning, I can just click the mouse on a feature, and the tool should give me the grid ref very accurately, and then pass the route to a GPS receiver, if I want to follow a route.  GetAMap provided by the OS presents mapping tiles that are 625pixels/km, thus giving a resolution of 1.6m per pixel.  So, if I can point my cursor to an accuracy of one pixel, I can generate a grid ref accurate to 1.6m... Not that the mapping imagery is anywhere near that accurate, of course...

Skills4Survival

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Re: A 1:25k vernier romer
« Reply #5 on: May 31, 2012, 06:56:52 PM »
Outside of marking a spot on the map, which also works (e.g. nice camp place/ dry firewood :-) you could make a grid reference or use the GPS to have a waypoint database for it over time, what I do now. I also use it for easy estimates on distance in combination with the scale used. You can also use it to draw in the magnetic declination in relation to the grid north.

But, I know what you mean. I use the map the same way (use surroundings) and have not really used grids outside of rough distance estimation, linked to experience to come to a more educated guess upfront.
Ivo

John-C

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Re: A 1:25k vernier romer
« Reply #6 on: June 01, 2012, 07:06:21 AM »
 GetAMap provided by the OS presents mapping tiles that are 625pixels/km, thus giving a resolution of 1.6m per pixel

......have I missed a setting on GetaMap - I wanted a grid ref a week or so a go & it only gave me 6 fig - does it do better?.  Although I did move the point arount to estimate 4/8 on where it changed, I found it easier to use Lyles tool!

captain paranoia

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Re: A 1:25k vernier romer
« Reply #7 on: June 01, 2012, 12:55:41 PM »
> have I missed a setting on GetaMap - I wanted a grid ref a week or so a go & it only gave me 6 fig - does it do better?

Ah, I was talking about the linear resolution that should be available from the resolution of the mapping images, not what GetAMap actually gives you ('ve not used it since it went all 'WheresThePath'...).  I think it's pretty piss-poor if it won't spit out a 10-figure reference; most other online mapping tools will (StreetMap, WheresThePath).