topic Re: Datum conversion from etrs89 to wgs84 in Developers Questions

Datum conversion from etrs89 to wgs84

RatikantaLenka — Thu, 25 Jun 2015 07:38:10 GMT

i have a chart with etrs89 coordinate system, i want to load the chart into wgs84 vector layer. Any one can help how to do this?

Re: Datum conversion from etrs89 to wgs84

DanPatterson_Retired — Thu, 25 Jun 2015 08:35:23 GMT

Do they both have a defined coordinate system? Define Projection—Help | ArcGIS for Desktop

Is the chart a raster? Project Raster—Help | ArcGIS for Desktop

Have you tried projecting the vector data? Project—Help | ArcGIS for Desktop

have you tried reversing the order of adding them to a new dataframe?

In any event, whatever format they are, they both need to have a defined coordinate system or they have to be projected to a common one

Re: Datum conversion from etrs89 to wgs84

ArnoldKuilman — Thu, 25 Jun 2015 09:32:35 GMT

Transformations between ETRS89 en WGS84 are not straight forward.

Comprehensive explanation: ETRS89 is a European system, fixed to the Eurasian plate, where WGS is an international system (ITRS). Since ETRS89 was realized until today (2012), a difference of 50 to 60 centimeters has accrued between WGS84/ITRS and ETRS89 which continues to grow dynamically at a rate of approximately 2.5 centimeters annually. The difference varies depending upon the location of a given coordinate on the Eurasian plate, because the continent slowly but steadily rotates around the Earth center of mass.

For direct measurements the conversion to or from ETRS89 is usually not necessary, as it in terms of the systemic high inaccuracy of several meters would not lead to a significant improvement. Here, the equating of WGS84 and ETRS89 can be tolerated.

If you have small scale maps where an error or mismatch between 0 till 60 centimetre is no problem, you can leave the coordinates as they are, and consider them as wgs84.

If you have large scale maps, where a high accuracy is necessary you need to take into account the epoch (datestamp) when the data was collected, and you need to find specific transformation parameters for that date.