Calculate inverse
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This guide explains how to use the Inverse tool in Emlid Flow and Emlid Flow 360 to calculate coordinate geometry data such as area, distance, azimuth, and more for known points.
Overview
The Inverse tool in Emlid Flow and Emlid Flow 360 allows you to calculate geometry data for existing points. The tool can assist you in such projects as planning civil or utility engineering works and monitoring construction progress.
The software calculates the following values based on the number of input points:
When you select two and more points:
 Direction (True North azimuth, Grid North azimuth)
 Slope distance (Slope Ground distance, Slope Grid distance)
 2D distance (2D Ground distance, 2D Grid distance)
 Height difference
 Grade
 Delta East (for points in a local CS only)
 Delta North (for points in a local CS only)
When you select three and more points:
 Slope distance (Slope Ground distance, Slope Grid distance)
 2D distance (2D Ground distance, 2D Grid distance)
 Area
 Slope perimeter
 2D perimeter
Depending on the coordinate system (CS) used in your project, different distance and azimuth types are used in the calculations:
CS type  Distance type  Azimuth type 

Global CS  Ground distance  True North azimuth 
Local CS  Grid distance  Grid North azimuth 
See our Introduction to coordinate systems guide to learn more about distance and azimuth types in different CSs.
When calculating area in a local coordinate system, the software applies a variation of the Shoelace formula, which approximates the area using trapezoids:
Area in a global coordinate system can be calculated for ellipsoid (on the ellipsoid surface) or ground (at the mean ground elevation). We use the method described in section 6 of Algorithms for geodesics by C. F. F. Karney (2013).
Workflow
 Emlid Flow
 Emlid Flow 360
To apply the Inverse tool in the Emlid Flow app, follow these steps:

Open the project in Emlid Flow.

Tap the tools button at the bottom left corner of the screen.

Tap Inverse.

Select the points you want to calculate the inverse for from the map or Objects list.
tipIn Emlid Flow & Emlid Flow 360 you can also find the pointtopoint, line, and closed line information for each line. To see this information, just tap on the line.

Click Review to see the calculated results. To calculate results for more than two points, use the arrow buttons to switch to a different set of two points.
noteThe displayed results will be different depending on the selected points. If you select 2 points, you'll see the pointtopoint calculations. If you select 3 points, you'll also see the calculations on the area, slope perimeter, etc.
noteYou can only use Closed line and Line for geometry measurements. It is not possible to import or export them as geometrical figures.
tipYou can change the order of the points in the Inverse section by dragging and dropping them. To delete a point, tap the delete button.

To exit the Inverse calculation mode, tap the close button in the upperright corner.
To apply the Inverse tool in the Emlid Flow 360 app, follow these steps:

Open the project in Emlid Flow 360.

Tap Inverse at the top of the screen to calculate the results.

Select the points you want to calculate the inverse for from the map or Objects list.
tipIn Emlid Flow & Emlid Flow 360 you can also find the pointtopoint, line, and closed line information for each line. To see this information, just tap on the line.

Find the calculated results on the right side of the screen. To calculate results for more than two points, use the arrow buttons to switch to a different set of two points.
noteThe displayed results will be different depending on the selected points. If you select 2 points, you'll see the pointtopoint calculations. If you select 3 points, you'll also see the calculations on the area, slope perimeter, etc.
noteYou can only use Closed line and Line for geometry measurements. It is not possible to import or export them as geometrical figures.
tipYou can change the order of the points in the Inverse section by dragging and dropping them. To delete a point, tap the delete button.

To exit the Inverse calculation mode, tap Cancel in the upperright corner.