From speed maps to plasma parameter errors: an update to the ISgeometry package by Ilkka Virtanen, University of Oulu The ISgeometry package was developed more than 10 yeas ago for purposes of EISCAT3D site selection. The package was used for producing measurement "speed maps" for different radar system configurations. The original package calculated ACF noise levels, which can be converted into standard deviations of fitted plasma parameters using precalculated lookup tables. We have developed an updated version of the package, which avoids the last step that users may find cumbersome. The updated package calculates estimates of plasma parameter uncertainties from radar system parameters and plasma parameters provided by the user. We introduce the basic working principle of ISgeometry, show some validation results, and present our estimates of plasma parameter uncertainties in the first light measurements of EISCAT3D.