source: trunk/README.GMAPS @ 953

Last change on this file since 953 was 953, checked in by kake, 15 years ago

Add config option to suppress inline maps on geotagged nodes (#188). Fix preferences to take notice of users turning off inline Google maps (#189).

File size: 2.3 KB
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1As of 0.52, OpenGuides supports Google Maps using the API. The support has a
2few rough edges that still need ironing out, mostly relating to ellipsoids,
3and for that reason they aren't exposed by default.
4
5To use Google Maps, you need to get an API key from
6http://www.google.com/apis/maps/signup.html. When you've put this value into
7the config file as gmaps_api_key, the maps become available to you in two
8places. Firstly, if you've set "show_gmap_in_node_display", and if the user
9has set their preferences to display Google Maps, any node which has
10location information will get an inset map pinpointing the location.
11Secondly, the URL
12http://.../wiki.cgi?action=index;format=map becomes a large map with a list
13of all nodes (regardless of the user settings). The latter will become very
14slow on any sizable guide (there is work being done on speeding up indexes
15in general - please see the mailing list). If you don't get maps displayed
16when you know that the node has location information, read on.
17
18Ellipsoids and map accuracy
19---------------------------
20
21If you are based in the US and inputting points using latitude/longitude,
22the values in your database will almost certainly correspond to points on
23Google Maps. If so, simply change the "ellipsoid" configuration variable
24to "WGS-84" if it's not already set to this, and your maps will display.
25
26If you are using the British Grid system things are more complicated and this
27support is incomplete. If you set the configuration variable force_wgs84
28to 1, maps will display, but points will be offset from where they should
29be, normally by about 50 metres. This is because the British Grid uses a
30different ellipsoid from Google Maps. We plan to integrate conversion
31routines to fix this in a future release. In the meantime, if you
32advertise the maps you must make users aware of this flaw and tell them
33not to try and "correct" location data!
34
35You may be unlucky enough to be using the UTM input modes (ie not British
36or Irish National Grid) but have data entered in a mixture of formats.
37This is likely if your users are from the UK, as you may find a mixture of
38WGS-84 and Airy (ie British Grid style) based nodes. In this case, you
39*do* need to correct any that are offset. Only do this if your users
40input Lat/long values rather than grid Eastings/Northings.
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