# Formula/ calculation for ESRI map coordinate conversion (meter to decimal degrees)

I'm new to ESRI mapping. I have a set of points in ESRI, with x, y, z coordinates, which I believe is in meters.

I am now writing an Android program, and I do not want to depend on ESRI, thus I would like to get the coordinates and pin them on Google map.

I have tried to use ESRI and export the coordinates to decimal degrees and pin them on Google map. But the position is not very accurate (varies from original position about 500m).

So I was thinking if there any hard coding calculations that I could do to convert meters to decimal degrees? I'm looking for accuracy at around 1m.

• need to know what projection 'your set of points' are in
– Mapperz
Nov 8 '13 at 4:12
• Sorry but isn't "meters" a kind of projection? In the ESRI program I could toggle from "meters" to "decimal degrees".... Nov 8 '13 at 7:50
• Because the points are off around 500 m, your projected data may be using a different geographic coordinate ref system / datum and are not being exported with an appropriate transformation to WGS84. We (and you!) need to know the CRS to help. Nov 8 '13 at 17:21
• Don't know if this will shield some light, I clicked open the data frame properties -> coordinate system, and it showed using Hong_Kong_1980_Grid, Transverse Mercator, Angular Unit: Degree (0.017453292519943299) Prime Meridian: Greenwich (0.000000000000000000) Datum: D_Hong_Kong_1980 Spheroid: International_1924 Nov 9 '13 at 4:20

The discrepancy you are seeing is because your original features are using a different coordinate system and datum than Google Maps.

To correct this you need to reproject your dataset to WGS84 which is pretty straight forward in ArcGIS as there is a tool available to do it. Check out this support article from Esri to see how to do it.

• Is there any way of hard coding/ doing calculation to it? Thanks!! Nov 11 '13 at 0:13

You don't want to do the calculation yourself. You should use a library.

Before you do that, you should know what a coordinate system is: http://en.wikipedia.org/wiki/Geographic_coordinate_system

When you have an idea what that is, work out what your coordinate system your original data is in. This is very important!

When you know what your original coordinate system is, you can use a transformation or reprojection in order to get those coordinates into the system that you want to use for Google Maps. The coordinate system you want to use is WGS84: http://spatialreference.org/ref/epsg/4327/. To convert data to this, use a GIS or use a library like Proj http://trac.osgeo.org/proj/ or OGR as a command line utility.

Halo, Perhaps before you export the coordinates (in meters)you need to change the layers data frame properties coordinate to WGS84 in your ArcMAP. Then you can export it out in KMZ format so you can display it in google earth. If you are using DMS should be OK instead of using DD. Thank you.