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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 § 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.


Projections is an iOS library for performing projection conversions between coordinates.

For conversions between geometries, see Simple Features Projections.


View the latest Appledoc

// CLLocationCoordinate2D coordinate = ...

PROJProjection *projection1 = [PROJProjectionFactory projectionWithAuthority:PROJ_AUTHORITY_EPSG
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
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];


Build & Test

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', '~> 1.0.4'

Pull from GitHub:

pod 'proj-ios', :git => '', :branch => 'master'
pod 'proj-ios', :git => '', :tag => '1.0.4'

Include as local project:

pod 'proj-ios', :path => '../projections-ios'


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)

Remote Dependencies