# Emlid Flow and cartesian coordinates

I have a Reach RS2 running firmware 31.8. I’m using Emlid Flow version 9.6.

The app and the web interface display the device’s position in longitude, latitude and ellipsoidal height. It used to be possible to switch to cartesian (x,y,z) coordinates but I can no longer see how to do this.

Is it possible to view the position in cartesian coordinates?

If not,what is Emlid’s recommended way to convert the results?

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Currently, it is not possible to view the position in geocentric. The only possible workaround, for now, is to use online coordinate converters. The proj library also allows you to do geodetic to cartesian coordinate conversion via CLI.

Cartesian coordinates are better for finding the distance between two positions. In any case, I believe that internally any GNSS device finds its position in cartesian terms, so if the result is shown in cartesian, there is no need for conversion and the inevitable small loss of accuracy.

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Do you need the distance between points in real-time, eg. during data collection? This sounds like one of the COGO features to me. We plan to support this in Emlid Flow, but since this is quite complex, the implementation will take some time.

I’m mainly interested in finding the location of a single fixed point. The reach user interface used to do that - you could switch between seeing the position in cartesian coordinates or latitude, longitude, height. For a base station you could also choose which format you use to set the location. For some reason, these choices were removed in a later version.

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Side note: You probably are aware, but those cartesian coordinates (x,y,z ECEF) have no sense of elevation and no sense of “level.” So, for most people they are not practical units, and require some kind of translation to make sense of them.

e.g. if you move your rover along a straight and level line on the earth’s surface, the x,y,z coordinates are all moving, including the z.

Yes, the two formats have different purposes. Longitude, latitude and height are great for finding your way around and (x,y,z) coordinates are great if you need the distance between two points.

Regards

Simon

Thanks for explaining! I can see how this feature could be useful. I’ll pass it on to the team for further discussion. I’ll let you know once we have any updates.

Thanks.

It’s worth saying that the user interface used to do this, so the functionality exists in earlier versions of the source code. For some reason it was removed, which I regards as a retrograde step. It was one of the advantage that the Reach range has over my Trimble Catalyst.

Regards

Simon

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