Overview

OSMapView provides an interface to Ordnance Survey OpenSpace maps, supporting the same mapping layers as the OpenSpace and OpenSpace Pro JavaScript APIs.

OSMapView is intended to provide a drop-in replacement for MapKit’s MKMapView and has a largely similar API. The API is as close as can it can be, while maintaintaining differentation with the use of the OS prefix (instead of MK) for all classes. In general, therefore, OSMapView is adequately documented by the MapKit documentation which cannot be reproduced here for copyright reasons. There are a few main differences:

• OSMapView uses the OSGB36 National Grid map projection. Applications which have assumed a Mercator projection may have to take the different projection into account.
• OSMapView does not support drawing maps outside the UK.
• OSMapView requires an API key and a tile source to be set before using the online data source.
• OSMapView supports many more map configurations than can be easily expressed with a single mapType property.
• OSMapView and OSOverlayView do not use power-of-2 zoom levels.
• OSMapView cannot be completely initialised from a NIB.
• OSGridPoint is in a specified coordinate system: it’s is a National Grid reference in metres.
• OSMapViewDelegate does not have map-loading callbacks.

Tile sources and API keys

OSMapView requires either an OS OpenSpace API key or a file containing map tiles in “OSTiles” format.

idOSTileSource tileSource = [OSMapView webTileSourceWithAPIKey:YOUR_API_KEY refererUrl:YOUR_PAGE_URL openSpacePro:false];
mapView.tileSources = [NSArray arrayWithObject:tileSource];

Coordinate conversions

OSGridPoint represents OSGB36 National Grid easting/northing (i.e. a “numeric-only” National Grid reference).

CLLocationCoordinate2D represents WGS84 latitude/longitude.

OSGB36 latitude/longitude is not currently supported. ETRS89 is not explicitly supported, but is closely approximated by WGS84.

Conversion between CLLocationCoordinate2D and OSGridPoint is largely handled internally — applications should not need to perform more conversions than with WGS84-based mapping APIs.

However, applications should be aware of the limitations of these conversions:

• The conversion is approximate. It is usually correct to within 3m compared to OSTN02.
• WGS84 lines of latitude/longitude are not aligned with National Grid. A consequence is that OSCoordinateRegion and OSGridRect represent different shapes, and thus cannot be interconverted accurately.
• The conversions used are subject to change (in particular, accuracy may be improved).

Applications should avoid unnecessary conversions. Coordinates should be stored in their source coordinate system in order to benefit from future accuracy improvements.

Subclassing notes

OSMapView is not designed to be subclassed.