Broken Star's diary

Recent diary entries

Somerset Levels and Moors (Part 2)

Posted by Broken Star on 19 March 2013 in English (English)

the current situation is that the boundary of the Somerset Levels and Moors is now relation 278627879.

At the time of writing this relation has the following ways as members: 207244544 207249332 54644027 207249333 207746811 207746818 207358221 207746813 190914419 29417895 207244546 153044009 153044010 72554425 148075256 207244538 207244543 Some of these were existing features (rivers) that I used as a boundary.

I also have (for the purposes of rendering) two ways tagged as natural=moor 208638587 - Western and Southern segment 210866783 - Middle segment

As a result of Potlatch misbehaving when trying to save an overlong way I also have the following ways created in error that probably ought to be deleted: 207882847 207881808 207881814 207882846

Somerset Levels and Moors (Part 1)

Posted by Broken Star on 19 March 2013 in English (English)

I thought I'd try and add this to the map, for two reasons. Firstly the search couldn't 't find it and secondly it didn't appear on the map so it couldn't be seen. It was as if the Somerset Levels and Moors did not exist.

I thought I could improve upon this situation. The first challenge was to identify the boundary.

I couldn't find an official definition of the boundary but I locally the area is notable as a low-lying area of wetlands. The only thing that google turned up was several extremely low-res approximation maps. I was disappointed to find that every map was slightly different.

With no official definition of the boundary I had to devise my own set of rules that would trace the boundary.

Looking at some of the out-of-copyright 'historic' maps (available as a background in Potlatch) showed that the Somerset Levels and Moors are criss-crossed with drainage channels. If you follow these to the edges there is a 25 foot (or 10 meter on some maps) contour. I decided to use this contour as the boundary.

My next major stumbling block was finding that there is a limit of 4000 nodes per way. Drawing the entire area as a single way was out of the question. I eventually ended up with a lot of untagged ways all members of a single relation. I tagged the relation as a National_Park but it did not render. I changed the tagging to natual=moor but it also did not render. However after a couple of days it did appear in a search so that was one of my original problems solved.

To be continued...