source: trunk/npemap.org.uk/static/FAQ.html @ 360

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Start on hard-to-find islands page

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5
6<h3>What is it?</h3>
7
8<p>There are a lot of applications on websites for being able to tell where
9people are from their postcode. For example "Where is my nearest
10B&amp;Q?". Unfortunately this data is expensive to licence (a few
11thousand pounds/year for a website). <a
12href="http://www.freethepostcode.org">Free the postcode</a> are doing a
13good job, but it is hard to contribute to their database as you
14need a GPS, so they have few postcodes.</p>
15
16<p>Our goal is to collect postcode data by getting users to locate
17themselves on a map of the country. They need only give the first part
18of their postcode, and if we can collect locations for all of these
19parts then we can create a database that is good enough for many
20applications. We are also accepting complete postcodes and 'partial'
21postcodes including the number portion of the second half of the postcode,
22in order to improve our accuracy.
23</p>
24
25<h3>What licence does the data have?</h3>
26
27<p>The data will be will be in the public domain; consequently, users
28submitting data agree to their submission being in the public domain
29when they enter their postcode.</p>
30
31<h3>What maps are you using?</h3>
32
33<p>We have scans of out of copyright OS maps of England and Wales.
34You can <a href="scotlandAndNI.html">register interest in future
35projects involving Scotland and Northern Ireland</a>.</p>
36
37<h3>So can I do what I like with your scans/tiles?</h3>
38
39<p>
40No. The scans and tiles have been placed under a
41<a href="tileLicence.html">licence</a>; they are not in the public
42domain.
43</p>
44
45<h3>Okay; I can use the tiles for some things; can I download the complete set?</h3>
46
47<p>
48Not yet. We need to make sure we've uncovered all the obvious flaws with
49the current tiles (eg human error in cropping and numbering the tiles)
50and have worked out an efficient distribution format.
51<a href="reportBug.html">Let us know</a> if you want to
52use the tiles; please don't try and crawl our tileserver to obtain the entire
53set.
54</p>
55
56<h3>Isn't orthowotsiting an old map hard?</h3>
57
58<p>Luckily we're going to work in the OSGB coordinate system that
59matches up with the grid lines on the map; this means we don't have to
60distort the maps too much. We also are not overly fussy about the
61accuracy, so this step can be done quickly.</p>
62
63<h3>Why don't you use maps created from <a
64href="http://www.openstreetmap.org">OpenStreetMap</a> data?</h3>
65
66<p>Because they are licensed under Creative Commons Share-alike
67licences, so we wouldn't be able to make our data public domain.</p>
68
69<p>There are people who believe that locating a point on a map creates a
70derived work, and hence requires a licence. We don't want to be the first
71to prove them wrong in a court, as that will be pricy.</p>
72
73<p>Also, the OpenStreetMap maps are not yet complete enough to achieve our
74goal of country-wide coverage.</p>
75
76<h3>Will this data be imported back into Free the Postcode?</h3>
77
78<p>Probably not directly. We are looking at the best way of presenting
79data from both projects whilst not polluting the Free the Postcode database
80with our lower accuracy data. We are importing Free the Postcode data into
81our database for display, but not re-exporting it currently.</p>
82
83<h3>If you are using scans of old maps, how accurate will the locations
84be?</h3>
85
86<p>Some of the scans are out by a degree or two but they are fairly
87good. We hope to be able to get better than 100 metres accuracy out of it in
88the end. This is more than good enough to locate a region as large as
89the first half of a postcode, and hopefully as much as the 'partial'
90postcodes described in the answer to 'What is it?' above.</p>
91
92<h3>My house isn't on a 1950s map</h3>
93
94<p>Find some local landmarks and guess where your house is. This is
95accurate enough for our purposes.</p>
96
97<h3>I know exactly where I am, and what my postcode is</h3>
98
99<p>If you have a GPS, enter your data into <a
100href="http://www.freethepostcode.org">Free the Postcode</a> and make the
101world a better place.</p>
102
103<h3>I can't seem to find a certain island on your overview map</h3>
104<p>We've put together a list of <a href="islands.html">hard to find
105 islands</a>, so you might well be able to find it from there.</p>
106
107<h3>So, how do I use it?</h3>
108
109<p>Find your location on our map, click where your postcode is, enter
110the postcode, agreeing to release your data.</p>
111
112<h3>Psst, I have a copy of the codepoint database. Wanna look?</h3>
113
114<p>No thanks, we want free data so we don't have to keep paying the nice
115codepoint people. </p>
116
117<h3>Won't you drive codepoint out of business?</h3>
118
119<p>We don't think so. There are a lot of places where this level of
120accuracy just isn't enough. Those people will still have to pay until
121<a href="http://www.freethepostcode.org">Free the Postcode</a> improves
122its coverage.</p>
123
124<h3>The map doesn't join up.</h3>
125
126<p>Yes, it isn't perfect. The OS didn't publish a single map of the whole
127country, so you have to scan then stick together data from several maps.
128We don't really know how to correct it perfectly. It would be really cool
129if someone could write software to detect the gridlines and automatically
130cut the images up on the lines and make them square.</p> 
131
132<h3>The wonkiness is so annoying it drives me mad, and I have experience of orthrectifying maps. Please let me straighten your maps.</h3>
133
134<p>Cool. Contact us, that would be great.</p>
135
136<h3>Why didn't you use proj/gdal?</h3>
137
138<p>Because we don't know how to work them. If you feel like improving how this
139works, let us know.</p>
140
141<h3>Why don't you have good mapping data of Scotland and Northern Ireland?</h3>
142
143<p>I don't think they were part of the New Popular Edition at 1 inch to the
144mile. If you have free higher resolution images of either of these places
145(we only have quarter inch to the mile) then we might be interested in them.</p>
146
147<h3>Who did the work?</h3>
148
149<ul>
150<li>Richard Fairhurst acquired and scanned the maps,</li>
151<li>Dominic Hargreaves and David Sheldon straightened and tiled the maps,</li>
152<li>Matthew Westcott, David Sheldon, Dominic Hargreaves and Nick Burch worked on the user interface and backend software.</li>
153</ul>
154
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