# Multi-Unit n:1 (mobile transmitter)

The Multi-Unit n:1 (mobile transmitter) case has any number of receivers on AUVs, ROVs or divers, with a single transmitter also on an AUV, ROV or diver.  

The position of each receiver relative to the transmitter is updated at 1 Hz.

If swarming, the best vertical results will be had by also using a pressure sensor for calculating depth.

The Mk II model is the only ROVL model that can operate in this configuration. The receivers and transmitter must periodically address the relative clock drift (every hour or two) by periodically surfacing and re-acquiring the GPS signal. 

This configuration is mostly useful for coordinating a swarm of AUVs or ROVs. The lead AUV or ROV carries the transmitter. The followers carry receivers, from which they can calculate their positions relative to the lead AUV or ROV (e.g., "I'm 50 meters southeast of the lead AUV"). The lead AUV or ROV can use its transmitted  ping ID payload to send a four-bit value to everyone in the swarm. This payload could be used to select predefined mission segments (e.g., "Hey everyone, we should be in phase 10 of the mission, which you already know means we all want to be heading at 272 degrees at 10 knots"), or it could be used to directly select one of 16 different headings, or whatever other clever ideas you can come up with.

If using only Cerulean-supplied equipment, the AUV/ROV/diver position is known only to the individual receiver. If you need to supply a follower AUV/ROV/diver position to the other units or to a topside monitoring system, then you must supply your own communication links and software support. 

{% hint style="info" %}
It is possible to run two independent sets of autosync-capable ROVLs in a single operating area, by running one set on channel A and one set on channel B.
{% endhint %}

{% hint style="info" %}
CeruleanTracker and CeruleanMap softwares do not support the n:1 configuration.  Users must write their own software to make use of the positional information supplied.
{% endhint %}

<figure><img src="/files/gcFZqMbIsMAVYXtVau7f" alt=""><figcaption><p>n Receivers tracking a single transmitter on a mobile platform, with optional receiver (dotted box) also tracking the transmitter</p></figcaption></figure>


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