Projections iOS
Projections Lib
The Projections Library was developed at the National Geospatial-Intelligence Agency (NGA) in collaboration with BIT Systems. The government has "unlimited rights" and is releasing this software to increase the impact of government investments by providing developers with the opportunity to take things in new directions. The software use, modification, and distribution rights are stipulated within the MIT license.
Pull Requests
If you'd like to contribute to this project, please make a pull request. We'll review the pull request and discuss the changes. All pull request contributions to this project will be released under the MIT license.
Software source code previously released under an open source license and then modified by NGA staff is considered a "joint work" (see 17 USC ยง 101); it is partially copyrighted, partially public domain, and as a whole is protected by the copyrights of the non-government authors and must be released according to the terms of the original open source license.
About
Projections is an iOS library for performing projection conversions between coordinates.
For conversions between geometries, see Simple Features Projections.
Usage
View the latest Appledoc
// CLLocationCoordinate2D coordinate = ...
PROJProjection *projection1 = [PROJProjectionFactory projectionWithAuthority:PROJ_AUTHORITY_EPSG
andIntCode:PROJ_EPSG_WEB_MERCATOR];
PROJProjection *projection2 = [PROJProjectionFactory projectionWithName:@"EPSG:4326"];
NSString *params = @" proj=tmerc lat_0=0 lon_0=121 k=0.99995 x_0=500000 y_0=0 ellps=clrk66 towgs84=-127.62,-67.24,-47.04,-3.068,4.903,1.578,-1.06 units=m no_defs";
PROJProjection *projection3 = [PROJProjectionFactory projectionWithAuthority:PROJ_AUTHORITY_EPSG
andIntCode:3123
andParams:params];
NSMutableString *definition = [NSMutableString string];
[definition appendString:@"PROJCS[\"Lambert_Conformal_Conic (1SP)\","];
[definition appendString:@"GEODCRS[\"GCS_North_American_1983\","];
[definition appendString:@"DATUM[\"North_American_Datum_1983\","];
[definition appendString:@"SPHEROID[\"GRS_1980\",6371000,0]],"];
[definition appendString:@"PRIMEM[\"Greenwich\",0],"];
[definition appendString:@"UNIT[\"Degree\",0.017453292519943295]],"];
[definition appendString:@"PROJECTION[\"Lambert_Conformal_Conic_1SP\"],"];
[definition appendString:@"PARAMETER[\"latitude_of_origin\",25],"];
[definition appendString:@"PARAMETER[\"central_meridian\",-95],"];
[definition appendString:@"PARAMETER[\"scale_factor\",1],"];
[definition appendString:@"PARAMETER[\"false_easting\",0],"];
[definition appendString:@"PARAMETER[\"false_northing\",0],"];
[definition appendString:@"PARAMETER[\"standard_parallel_1\",25],"];
[definition appendString:@"UNIT[\"Meter\",1],AUTHORITY[\"EPSG\",\"9801\"]]"];
PROJProjection *projection4 = [PROJProjectionFactory projectionByDefinition:definition];
PROJProjectionTransform *transform = [projection1 transformationWithProjection:projection2];
PROJProjectionTransform *inverseTransform = [transform inverseTransformation];
CLLocationCoordinate2D transformed = [transform transform:coordinate];
CLLocationCoordinate2D inverseTransformed = [inverseTransform transform:transformed];
[transform destroy];
[inverseTransform destroy];
Build
IMPORTANT -
Be sure your Mac has the autoconf, automake, and glibtoolize utilities. These are required to build
the proj4-ios dependency. Without them, pod install will fail. The easiest way to get these is to brew install them:
brew install automake
brew install libtool
Build this repository using Xcode and/or CocoaPods:
pod repo update
pod install
Open proj-ios.xcworkspace in Xcode or build from command line:
xcodebuild -workspace 'proj-ios.xcworkspace' -scheme proj-ios build
Run tests from Xcode or from command line:
xcodebuild test -workspace 'proj-ios.xcworkspace' -scheme proj-ios -destination 'platform=iOS Simulator,name=iPhone 14'
Include Library
See the above note about automake and glibtoolize.
Include this repository by specifying it in a Podfile using a supported option.
Pull from CocoaPods:
pod 'proj-ios', '~> 2.0.0'
Pull from GitHub:
pod 'proj-ios', :git => 'https://github.com/ngageoint/projections-ios.git', :branch => 'master'
pod 'proj-ios', :git => 'https://github.com/ngageoint/projections-ios.git', :tag => '2.0.0'
Include as local project:
pod 'proj-ios', :path => '../projections-ios'
Swift
To use from Swift, import the proj-ios bridging header from the Swift project's bridging header
#import "proj-ios-Bridging-Header.h"
// CLLocationCoordinate2D coordinate = ...
let projection1 : PROJProjection = PROJProjectionFactory.projection(withAuthority: PROJ_AUTHORITY_EPSG, andIntCode: PROJ_EPSG_WEB_MERCATOR)
let projection2 : PROJProjection = PROJProjectionFactory.projection(withName: "EPSG:4326")
let projection3 : PROJProjection = PROJProjectionFactory.projection(withAuthority: PROJ_AUTHORITY_EPSG, andIntCode: 3123,
andParams: " proj=tmerc lat_0=0 lon_0=121 k=0.99995 x_0=500000 y_0=0 ellps=clrk66 "
" towgs84=-127.62,-67.24,-47.04,-3.068,4.903,1.578,-1.06 units=m no_defs")
let projection4 : PROJProjection = PROJProjectionFactory.projection(byDefinition: "PROJCS[\"Lambert_Conformal_Conic (1SP)\","
"GEODCRS[\"GCS_North_American_1983\","
"DATUM[\"North_American_Datum_1983\","
"SPHEROID[\"GRS_1980\",6371000,0]],"
"PRIMEM[\"Greenwich\",0],"
"UNIT[\"Degree\",0.017453292519943295]],"
"PROJECTION[\"Lambert_Conformal_Conic_1SP\"],"
"PARAMETER[\"latitude_of_origin\",25],"
"PARAMETER[\"central_meridian\",-95],"
"PARAMETER[\"scale_factor\",1],"
"PARAMETER[\"false_easting\",0],"
"PARAMETER[\"false_northing\",0],"
"PARAMETER[\"standard_parallel_1\",25],"
"UNIT[\"Meter\",1],AUTHORITY[\"EPSG\",\"9801\"]]")
let transform : PROJProjectionTransform = projection1.transformation(with: projection2)
let inverseTransform : PROJProjectionTransform = transform.inverseTransformation()
let transformed : CLLocationCoordinate2D = transform.transform(coordinate)
let inverseTransformed : CLLocationCoordinate2D = inverseTransform.transform(transformed)
transform.destroy()
inverseTransform.destroy()
Remote Dependencies
- PROJ (The MIT License (MIT)) - Cartographic projection software
- Coordinate Reference Systems (The MIT License (MIT)) - Coordinate Reference Systems Library