<p>This work presents a <strong>survey </strong>for the indoor localization systems handling multi-floor environments, including <em>floor localization</em>, and <em>estimating the floor and the 2D location of the user</em>. It focuses on approaches targetting users and user devices. </p>
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<p>The survey comprehensively covers various techniques and technologies focusing especially on the recent solutions to give insights to the researchers for further development in the domain of indoor localization.</p>
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<p>Finally, several challenges are addressed and possible solutions are proposed pointing to future research directions.</p>
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<p>No data was collected for this work.</p>