# Transmitter & GPS Topside and Receiver Deepside

In the case where the transmitter is topside with a co-located GPS, and the receiver is deepside, and the GPS data can be downlinked to the deepside system, the location of the receiver can be computed. The process is almost identical to the above case, with the positions reversed. The changes to the above case look like this:

latitude\_tx :: from GPS co-located with transmitter (in degrees that include minutes and seconds)

longitude\_tx :: from GPS co-located with transmitter (in degrees that include minutes and seconds)

long\_m\_per\_deg = lat\_m\_per\_deg x cos(latitude\_tx)      // meters per degree of longitude    \[note 1]

latitude\_rx = latitude\_tx + (sin(bearing + 180°) x map\_radius / lat\_m\_per\_deg) \[note 1, 2]

longitude\_rx = longitude\_tx + (cos(bearing + 180°) x map\_radius / long\_m\_per\_deg  \[note 1, 2]

{% hint style="info" %}
Note 1: Remember, most computer functions require you to convert degrees to radians
{% endhint %}

{% hint style="info" %}
Note 2: the signs of the degrees as noted above are needed in the computations
{% endhint %}

{% hint style="info" %}
Note 3: longitude degrees that are West are negative, East are positive. Latitude degrees that are North are positive, South are negative.
{% endhint %}


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