Map of Yorkshire Caves

[bill chadwick]

Yes the difference in projection is important.

On Mercator / Google Maps True North is straight up the screen.

Most UK cave surveys are done referenced to UK grid north which is not straight up the screen on Google Maps see http://tinyurl.com/2s2f99

As a minimum the survey must be rotated by the Convergence value (difference between UK grid North and True North) at the survey's approximate centre before it can be accurately overlayed. Convergence can be readily computed for any point on the UKOS projection - an average value for a sheet is shown in the marginalia of printed OS maps. Convergence is very small around the central meridean of the projection (2 degrees West) and the York Dales are at approx 2.25W.

If you use MapCruncher to set the correspondances between cave survey and point on the ground then it will do all the necessary rubber sheeting from UKOS to Mercator for you. You need to give at least 6 correspondances (use survey corners, entrances etc.) to get good results.

 

[footleg]

So presumably you believe that anyone who publishes a grid reference gained from an Ordnance Survey map in a guide book is in breach of copyright for exactly the same reasons?

Fortunately for the rest of us, it would seem that the Ordnance Survey don't agree. It all comes down to fair use...

Whoa! I'm not in any way a legal expert, and I'm not saying I believe anything so specific. I am just saying that you need to consider these matters carefully before published data. Somewhere between publishing a single grid reference and putting enough grid references together in a data file that you are essentially describing all the features on a map, you are going to cross a line between fair use and breach of copyright. If you gathered all that data yourself by going out and measuring the landscape yourself then you own rights to that data. If you take it all off an OS map then you don't. Maybe you are technically in breach of copyright if you take one grid reference off a map? But the OS might allow you to do so because it is part of the value of purchasing their mapping products?

I am not saying what is or isn't allowed, nor accusing anyone of doing anything I might consider wrong. Just raising the point that you need to consider carefully what you publish and where you get it from. Maybe someone on this forum has some legal training and can comment one whether publishing cave locations derived from Googlemaps aerial photographs is fair use or breaching copyright?

 

[littlebear]

Check this out:

v.cool

 

[Cave Mapper]

New features:

• Some cave locations have been corrected (e.g. Borrins Moor is no longer in the Irish Sea)
• All the locations that are based on 6 figure grid references are now more accurately placed (+/- 50m), previously they could be between 0 and 100m out
• The data files containing the location coordinates can now be downloaded
• The data is also provided in KML format for viewing in Google Earth. Here's some screen shots http://cavemaps.50webs.com/googleearth.htm
  

 

[Cave Mapper]

Footleg's GPS data for West Kingsdale, Easegill, Marble Steps and other areas is now online

 

[bill chadwick]

I have just posted some fairly detailed instructions on how to get cave overlays on to Google Maps at http://www.bdcc.co.uk/GoogleCrunch/Crunch.htm

Bill

 

[footleg]

Incredibly useful Bill, as always! I'm creating my tiles from massive bitmaps in photoshop because I the large area I am working with, but your code examples for adding custom map types saved me a whole lot of work.

 

[Cave Mapper]

CaveMaps.org is now more intuitive

 

[Cave Mapper]

Most of the Alum Pot area and Allotment entrances are now placed with pinpoint accuracy