How to define a local coordinate system by known points

In our previous post, we shared tips on how to set up a correct local coordinate system (CS) for your country. Today we want to provide you with steps you can take if you have a problem defining the required local coordinate system for your survey project.

Steps to take if you are completely unfamiliar with the local CS parameters

Suppose you need to survey an area, but you don’t know which local coordinate system to use. There is no projection or vertical datum available, you only have benchmarks with projected coordinates. Is there a way out? Yes, there is. You can still perform a survey using the localization feature in the Emlid Flow app, available with the Survey subscription. It allows you to calculate the parameters and survey in the coordinate system specific to that area.

The workflow is straightforward:

  1. Select Global CS for your project.
  2. Add manually or import known points to the project.
  3. Collect the same points in RTK.
  4. Go to Project localization.
  5. Pair known and control points.
  6. Analyze the residuals.
  7. Apply localization.

Learn more details in our guide on applying localization in Emlid Flow.

Steps to take if you’re not sure about the used local CS

There’s another case where localization will help you—when you’re not sure it’s exactly the same CS you need. For example, you know that the benchmarks have shifted over time but you still need to adjust to them. This can also be solved by localization.

The workflow is the same as above with the only exception—specify the on-hand or supposed projection and/or datum for your project and adjust the project based on the benchmarks.

Steps to take if you want to work in a CS with a false origin

And here is the last case. Let’s say you have a layout of house made using CAD in a CS with a false origin and you need to set it out in a certain area. No need to guess what will help you here.

Select Global CS for your project, import the known points in a CS with false origin to the project, collect the same points in RTK, and apply localization in the Emlid Flow app.

General instructions

The only thing you should always keep in mind is that localization depends on many factors—known points distribution, their quality, distortions of the local CS, etc. Read the instructions in our guide to get the highest possible accuracy. Got questions? Feel free to contact us at

If you have already tried localization, share your experience with us in the comments below.