| 1 | As of 0.52, OpenGuides supports Google Maps using the API. The support has a |
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| 2 | few rough edges that still need ironing out, mostly relating to ellipsoids, |
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| 3 | and for that reason they aren't exposed by default. |
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| 4 | |
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| 5 | To use Google Maps, you need to get an API key from |
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| 6 | http://www.google.com/apis/maps/signup.html. When you've put this value into |
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| 7 | the config file as gmaps_api_key, the maps become available to you in two |
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| 8 | places. Firstly, if the user has set the user preference to display Google |
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| 9 | Maps, any node which has location information will get an inset map |
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| 10 | pinpointing the location. Secondly, the URL |
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| 11 | http://.../wiki.cgi?action=index;format=map becomes a large map with a list |
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| 12 | of all nodes (regardless of the user settings). The latter will become very |
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| 13 | slow on any sizable guide (there is work being done on speeding up indexes |
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| 14 | in general - please see the mailing list). If you don't get maps displayed |
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| 15 | when you know that the node has location information, read on. |
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| 16 | |
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| 17 | Ellipsoids and map accuracy |
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| 18 | --------------------------- |
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| 19 | |
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| 20 | If you are based in the US and inputting points using latitude/longitude, |
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| 21 | the values in your database will almost certainly correspond to points on |
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| 22 | Google Maps. If so, simply change the "ellipsoid" configuration variable |
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| 23 | to "WGS-84" if it's not already set to this, and your maps will display. |
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| 24 | |
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| 25 | If you are using the British Grid system things are more complicated and this |
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| 26 | support is incomplete. If you set the configuration variable force_wgs84 |
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| 27 | to 1, maps will display, but points will be offset from where they should |
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| 28 | be, normally by about 50 metres. This is because the British Grid uses a |
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| 29 | different ellipsoid from Google Maps. We plan to integrate conversion |
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| 30 | routines to fix this in a future release. In the meantime, if you |
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| 31 | advertise the maps you must make users aware of this flaw and tell them |
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| 32 | not to try and "correct" location data! |
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| 33 | |
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| 34 | You may be unlucky enough to be using the UTM input modes (ie not British |
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| 35 | or Irish National Grid) but have data entered in a mixture of formats. |
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| 36 | This is likely if your users are from the UK, as you may find a mixture of |
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| 37 | WGS-84 and Airy (ie British Grid style) based nodes. In this case, you |
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| 38 | *do* need to correct any that are offset. Only do this if your users |
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| 39 | input Lat/long values rather than grid Eastings/Northings. |
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