How can I accurately determine the Hoist altitude on a 70 storey building


I am trying to measure the altitude of a Hoist elevator ( on 200m high building), by installing sensors on top of it and publishing the altitude to the cloud using Particle Photon. Could someone please suggest a reliable way of measuring the hoist/elevator altitude. Below are the options that I am aware of:

1. Using Barometric pressure sensors (Installing a pressure sensor on the Ground level and one on the hoist); Calculate the altitude based on difference in pressure. As the building is 200m high, I am concerned about accuracy due to high wind speeds, temperature variation etc.
2. Laser Range finder: I am not aware of any off the shelf products, that I can connect with Spark electron, to measure that altitude.
3. RTK GPS: I learnt that the accuracy is in cm’s on flat surface, but unsure about accuracy in measuring height. Again, as there are building around, getting satellite signals would not be reliable.

Below is the image showing the hoist going up on a construction site.

Thank you.

You might take a look here:

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I know my Phontom 4 Drone and many others use Barometric pressure to maintain their altitude when GPS is not avaliable and it does a really good job at maintaining the proper height. I would for sure test one of CE’s sensors out since they provide the code needed to work with the Photon or Electron.

Let us know how it goes.

Also how will you use this data?

How accurate and repeatable does it have to be? Also, what are the consequences of being wrong? Barometric pressure changes all the time in the real world… If a storm comes up and changes the barometric pressure significantly, you could be off by hundreds of feet. I’d recommend that as the elevator goes up and down, you at least have a known point that somehow gets detected to calibrate your system to a known altitude, even if it’s just an “end stop” switch at the bottom, and maybe even have a stationary pressure sensor on the roof at a known point to do a difference calculation between sensor 1 and sensor 2. That would be way more accurate than just an arbitrary sensor riding up and down.

Is there any way to measure how much cable is out ? Like the
height of the cable on the spool ?

@Falcon, are you looking for the altitude or which floor the elevator is on? What about an optical proximity sensor that trips when its light bounces off each floor slab as the elevator goes up or down. Or add reflecting tape at each floor where a sensor could bounce light off of it. These would allow you to count the floors the elevator passed.

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