A position fix for a mobile platform is determined using RSSI values for wireless signals received from access points (APs), at least one of which has dynamic transmission power control. The transmission power data for the APs is received from an entity separate from the APs, e.g., a central entity or a positioning assistance server. The RSSI values for wireless signals received from the APs are acquired, as is an RSSI heatmap. Using the transmission power data, the RSSI values and the RSSI heatmap, the position fix for the mobile platform is determined. The position fix may be determined by the mobile platform or a positioning assistance server. Additionally, a server may receive transmission power data for APs and may provide to a mobile platform RSSI heatmap information based on the transmission power data. The RSSI heatmap information may be, e.g., the transmission power data or a RSSI heatmap.