Using arcgis iOS longitude and latitude to show location results in a incorrect location

Question

all

I am new to arcgis for iOS, now I encounter a strange problem, and I have looked into other threads but haven't find any solutions.

I want to show a building whose longitude is 116.929167 and latitude is 34.727222 on my graphic layer. My base map layer is in a WGS84 spatial reference.

However, when I first tried the following code, it results in the point being misplaced. Note: the place is somewhere in Jangsu Province, China, but it was placed in Hunan Province, China.

//create an instance of a tiled map service layer
AGSTiledMapServiceLayer *tiledLayer = [[AGSTiledMapServiceLayer alloc] initWithURL:[NSURL URLWithString:kTiledMapServiceURL]];

//Add it to the map view
[self.mapView addMapLayer:tiledLayer withName:@"Tiled Layer"];

//release to avoid memory leaks

//set the callout delegate so we can display callouts
self.mapView.callout.delegate = self;

//add  graphics layer for the graphics
self.graphicsLayer = [AGSGraphicsLayer graphicsLayer];

//add the graphics layer to the map
[self.mapView addMapLayer:self.graphicsLayer withName:@"Graphics Layer"];

//zoom to china
AGSEnvelope *chinaEnv = [AGSEnvelope envelopeWithXmin:78.0000000
                                                ymin:0.4400000
                                                xmax:156.0000000
                                                ymax:75.0000000
                                    spatialReference:[AGSSpatialReference wgs84SpatialReference]];

[self.mapView zoomToEnvelope:chinaEnv animated:YES];

self.mapView.callout.customView = nil;

self.mapView.callout.accessoryButtonHidden = YES;

double longitude = 116.929167;
double latitude = 34.727222;

AGSPoint *graphicPoint = [AGSPoint pointWithX:longitude y:latitude spatialReference:[AGSSpatialReference wgs84SpatialReference]];

[self.mapView.callout showCalloutAt:graphicPoint screenOffset:CGPointMake(0, 0) animated:YES];

Can anyone tell me why it cannot show the correct location and how to fix this problem? Thank you very much for your time and answers! Best Regards.

Answer 1

I am afraid that you have confused between WGS84 Web Mercator and WGS84.

• WGS84 Web Mercator: it is a Projected Coordinate System, which is used by the most of the world map(google, esri, bing)
• WGS84:latitude/longitude

so back to your question, I think your basemap is WGS84 Web Mercator. but your mappoint is wgs84SpatialReference. you have to project it.

wish this solves your problem.