We consider a daylight-adaptive lighting control system to adapt dimming levels of artificial light sources with changing daylight, under illumination constraints specified at the horizontal workspace plane of an occupant. We propose a control method for achieving a minimum illuminance at the workspace plane using illuminance measurements at light sensors situated at the ceiling, and additional prior-information from sensor calibration. The proposed method results in a linear programming optimization problem with inequality constraints. Using simulations with photometric data, we compare our sub-optimum solution with the solution where knowledge of the illuminance mapping from the light sensors to workspace illuminance values is available, and with a reference method that is based on satisfying illuminance constraints specified at the light sensors. (C) 2014 Elsevier B.V. All rights reserved.