# Determining Atmospheric Pressure from UWI

In the previous blog post we went through a couple examples outlining the importance of having the correct atmospheric pressure entered into an Electronic Flow Meter’s configuration. So how do we go about determining the correct atmospheric pressure at a given location?

Some EFMs have built in capability to determine atmospheric pressure based on elevation. Assuming the technician on location had access to a GPS it would stand to reason they could determine their current elevation and rely on the flow computer to do the rest. This works well enough, but what if the technician doesn’t have access to a GPS, or what if the flow computer is incapable of calculating atmospheric pressure based off of elevation?

This blog post will show one way to determine atmospheric pressure given only a UWI.

**Step #1 – convert the UWI into GPS coordinates**

For the purpose of this example let’s choose a random location: *100/03-22-040-24w4/00*

There are several tools available online to perform this function, I prefer this one made available for free from the Government of Alberta.

As shown in the screenshot below I have entered the coordinates into the associated fields.

After clicking the convert button, you will be presented with a myriad of information. For the purpose of our example scroll down to the bottom to find the latitude and longitude equivalent of our UWI. (Pictured Below)

As per the note above we now know that our GPS coordinates for this UWI are 52.4505285, -113.3784738.

If you were to punch these coordinates into Google Maps you could also quickly get a satellite view of this location.

**Step #2 – use GPS coordinates to determine elevation**

Now that we know the GPS coordinates of the UWI we are able to determine the elevation by references one of several databases made available to the general public. I prefer this one. GPS Visualizer is a very powerful website. In a future post I will explore some of the features available and how they can be of benefit to the energy industry.

As shown in the picture below we are only converting one set of coordinates, so we will use the ‘Single-point elevation lookup:’.

Using this tool we find our elevation at this UWI to be 877 M.

**Step #3 – Math**

The final step is to perform the same math the flow computer uses to determine atmospheric pressure.

Referring back to our previous example’s base pressure and temperature (101.325 kPa / 15° C ) and assuming pressure is measured in kPa and elevation is expressed in meters, the following formula can be used:

**Pressure = 101.56 – 0.0113 * Elevation**

Our atmospheric pressure at this location works out to be 91.6499 kPa.

### Conclusion

This is an easy enough process for an individual location but isn’t something I would wish to repeat for multiple UWI’s. Watch for the next post where I will show how to convert bulk amounts of data and represent it geographically.

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